/* * kernel/sched/core.c * * Kernel scheduler and related syscalls * * Copyright (C) 1991-2002 Linus Torvalds * * 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and * make semaphores SMP safe * 1998-11-19 Implemented schedule_timeout() and related stuff * by Andrea Arcangeli * 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar: * hybrid priority-list and round-robin design with * an array-switch method of distributing timeslices * and per-CPU runqueues. Cleanups and useful suggestions * by Davide Libenzi, preemptible kernel bits by Robert Love. * 2003-09-03 Interactivity tuning by Con Kolivas. * 2004-04-02 Scheduler domains code by Nick Piggin * 2007-04-15 Work begun on replacing all interactivity tuning with a * fair scheduling design by Con Kolivas. * 2007-05-05 Load balancing (smp-nice) and other improvements * by Peter Williams * 2007-05-06 Interactivity improvements to CFS by Mike Galbraith * 2007-07-01 Group scheduling enhancements by Srivatsa Vaddagiri * 2007-11-29 RT balancing improvements by Steven Rostedt, Gregory Haskins, * Thomas Gleixner, Mike Kravetz */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_PARAVIRT #include #endif #include "sched.h" #include "../workqueue_internal.h" #include "../smpboot.h" #define CREATE_TRACE_POINTS #include DEFINE_MUTEX(sched_domains_mutex); DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); static void update_rq_clock_task(struct rq *rq, s64 delta); void update_rq_clock(struct rq *rq) { s64 delta; lockdep_assert_held(&rq->lock); if (rq->clock_skip_update & RQCF_ACT_SKIP) return; delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; if (delta < 0) return; rq->clock += delta; update_rq_clock_task(rq, delta); } /* * Debugging: various feature bits */ #define SCHED_FEAT(name, enabled) \ (1UL << __SCHED_FEAT_##name) * enabled | const_debug unsigned int sysctl_sched_features = #include "features.h" 0; #undef SCHED_FEAT /* * Number of tasks to iterate in a single balance run. * Limited because this is done with IRQs disabled. */ const_debug unsigned int sysctl_sched_nr_migrate = 32; /* * period over which we average the RT time consumption, measured * in ms. * * default: 1s */ const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC; /* * period over which we measure -rt task cpu usage in us. * default: 1s */ unsigned int sysctl_sched_rt_period = 1000000; __read_mostly int scheduler_running; /* * part of the period that we allow rt tasks to run in us. * default: 0.95s */ int sysctl_sched_rt_runtime = 950000; /* cpus with isolated domains */ cpumask_var_t cpu_isolated_map; /* * this_rq_lock - lock this runqueue and disable interrupts. */ static struct rq *this_rq_lock(void) __acquires(rq->lock) { struct rq *rq; local_irq_disable(); rq = this_rq(); raw_spin_lock(&rq->lock); return rq; } /* * __task_rq_lock - lock the rq @p resides on. */ struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf) __acquires(rq->lock) { struct rq *rq; lockdep_assert_held(&p->pi_lock); for (;;) { rq = task_rq(p); raw_spin_lock(&rq->lock); if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rf->cookie = lockdep_pin_lock(&rq->lock); return rq; } raw_spin_unlock(&rq->lock); while (unlikely(task_on_rq_migrating(p))) cpu_relax(); } } /* * task_rq_lock - lock p->pi_lock and lock the rq @p resides on. */ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) __acquires(p->pi_lock) __acquires(rq->lock) { struct rq *rq; for (;;) { raw_spin_lock_irqsave(&p->pi_lock, rf->flags); rq = task_rq(p); raw_spin_lock(&rq->lock); /* * move_queued_task() task_rq_lock() * * ACQUIRE (rq->lock) * [S] ->on_rq = MIGRATING [L] rq = task_rq() * WMB (__set_task_cpu()) ACQUIRE (rq->lock); * [S] ->cpu = new_cpu [L] task_rq() * [L] ->on_rq * RELEASE (rq->lock) * * If we observe the old cpu in task_rq_lock, the acquire of * the old rq->lock will fully serialize against the stores. * * If we observe the new cpu in task_rq_lock, the acquire will * pair with the WMB to ensure we must then also see migrating. */ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rf->cookie = lockdep_pin_lock(&rq->lock); return rq; } raw_spin_unlock(&rq->lock); raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags); while (unlikely(task_on_rq_migrating(p))) cpu_relax(); } } #ifdef CONFIG_SCHED_HRTICK /* * Use HR-timers to deliver accurate preemption points. */ static void hrtick_clear(struct rq *rq) { if (hrtimer_active(&rq->hrtick_timer)) hrtimer_cancel(&rq->hrtick_timer); } /* * High-resolution timer tick. * Runs from hardirq context with interrupts disabled. */ static enum hrtimer_restart hrtick(struct hrtimer *timer) { struct rq *rq = container_of(timer, struct rq, hrtick_timer); WARN_ON_ONCE(cpu_of(rq) != smp_processor_id()); raw_spin_lock(&rq->lock); update_rq_clock(rq); rq->curr->sched_class->task_tick(rq, rq->curr, 1); raw_spin_unlock(&rq->lock); return HRTIMER_NORESTART; } #ifdef CONFIG_SMP static void __hrtick_restart(struct rq *rq) { struct hrtimer *timer = &rq->hrtick_timer; hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED); } /* * called from hardirq (IPI) context */ static void __hrtick_start(void *arg) { struct rq *rq = arg; raw_spin_lock(&rq->lock); __hrtick_restart(rq); rq->hrtick_csd_pending = 0; raw_spin_unlock(&rq->lock); } /* * Called to set the hrtick timer state. * * called with rq->lock held and irqs disabled */ void hrtick_start(struct rq *rq, u64 delay) { struct hrtimer *timer = &rq->hrtick_timer; ktime_t time; s64 delta; /* * Don't schedule slices shorter than 10000ns, that just * doesn't make sense and can cause timer DoS. */ delta = max_t(s64, delay, 10000LL); time = ktime_add_ns(timer->base->get_time(), delta); hrtimer_set_expires(timer, time); if (rq == this_rq()) { __hrtick_restart(rq); } else if (!rq->hrtick_csd_pending) { smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); rq->hrtick_csd_pending = 1; } } #else /* * Called to set the hrtick timer state. * * called with rq->lock held and irqs disabled */ void hrtick_start(struct rq *rq, u64 delay) { /* * Don't schedule slices shorter than 10000ns, that just * doesn't make sense. Rely on vruntime for fairness. */ delay = max_t(u64, delay, 10000LL); hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), HRTIMER_MODE_REL_PINNED); } #endif /* CONFIG_SMP */ static void init_rq_hrtick(struct rq *rq) { #ifdef CONFIG_SMP rq->hrtick_csd_pending = 0; rq->hrtick_csd.flags = 0; rq->hrtick_csd.func = __hrtick_start; rq->hrtick_csd.info = rq; #endif hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); rq->hrtick_timer.function = hrtick; } #else /* CONFIG_SCHED_HRTICK */ static inline void hrtick_clear(struct rq *rq) { } static inline void init_rq_hrtick(struct rq *rq) { } #endif /* CONFIG_SCHED_HRTICK */ /* * cmpxchg based fetch_or, macro so it works for different integer types */ #define fetch_or(ptr, mask) \ ({ \ typeof(ptr) _ptr = (ptr); \ typeof(mask) _mask = (mask); \ typeof(*_ptr) _old, _val = *_ptr; \ \ for (;;) { \ _old = cmpxchg(_ptr, _val, _val | _mask); \ if (_old == _val) \ break; \ _val = _old; \ } \ _old; \ }) #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) /* * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, * this avoids any races wrt polling state changes and thereby avoids * spurious IPIs. */ static bool set_nr_and_not_polling(struct task_struct *p) { struct thread_info *ti = task_thread_info(p); return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); } /* * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set. * * If this returns true, then the idle task promises to call * sched_ttwu_pending() and reschedule soon. */ static bool set_nr_if_polling(struct task_struct *p) { struct thread_info *ti = task_thread_info(p); typeof(ti->flags) old, val = READ_ONCE(ti->flags); for (;;) { if (!(val & _TIF_POLLING_NRFLAG)) return false; if (val & _TIF_NEED_RESCHED) return true; old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED); if (old == val) break; val = old; } return true; } #else static bool set_nr_and_not_polling(struct task_struct *p) { set_tsk_need_resched(p); return true; } #ifdef CONFIG_SMP static bool set_nr_if_polling(struct task_struct *p) { return false; } #endif #endif void wake_q_add(struct wake_q_head *head, struct task_struct *task) { struct wake_q_node *node = &task->wake_q; /* * Atomically grab the task, if ->wake_q is !nil already it means * its already queued (either by us or someone else) and will get the * wakeup due to that. * * This cmpxchg() implies a full barrier, which pairs with the write * barrier implied by the wakeup in wake_up_q(). */ if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL)) return; get_task_struct(task); /* * The head is context local, there can be no concurrency. */ *head->lastp = node; head->lastp = &node->next; } void wake_up_q(struct wake_q_head *head) { struct wake_q_node *node = head->first; while (node != WAKE_Q_TAIL) { struct task_struct *task; task = container_of(node, struct task_struct, wake_q); BUG_ON(!task); /* task can safely be re-inserted now */ node = node->next; task->wake_q.next = NULL; /* * wake_up_process() implies a wmb() to pair with the queueing * in wake_q_add() so as not to miss wakeups. */ wake_up_process(task); put_task_struct(task); } } /* * resched_curr - mark rq's current task 'to be rescheduled now'. * * On UP this means the setting of the need_resched flag, on SMP it * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ void resched_curr(struct rq *rq) { struct task_struct *curr = rq->curr; int cpu; lockdep_assert_held(&rq->lock); if (test_tsk_need_resched(curr)) return; cpu = cpu_of(rq); if (cpu == smp_processor_id()) { set_tsk_need_resched(curr); set_preempt_need_resched(); return; } if (set_nr_and_not_polling(curr)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); } void resched_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; if (!raw_spin_trylock_irqsave(&rq->lock, flags)) return; resched_curr(rq); raw_spin_unlock_irqrestore(&rq->lock, flags); } #ifdef CONFIG_SMP #ifdef CONFIG_NO_HZ_COMMON /* * In the semi idle case, use the nearest busy cpu for migrating timers * from an idle cpu. This is good for power-savings. * * We don't do similar optimization for completely idle system, as * selecting an idle cpu will add more delays to the timers than intended * (as that cpu's timer base may not be uptodate wrt jiffies etc). */ int get_nohz_timer_target(void) { int i, cpu = smp_processor_id(); struct sched_domain *sd; if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu)) return cpu; rcu_read_lock(); for_each_domain(cpu, sd) { for_each_cpu(i, sched_domain_span(sd)) { if (cpu == i) continue; if (!idle_cpu(i) && is_housekeeping_cpu(i)) { cpu = i; goto unlock; } } } if (!is_housekeeping_cpu(cpu)) cpu = housekeeping_any_cpu(); unlock: rcu_read_unlock(); return cpu; } /* * When add_timer_on() enqueues a timer into the timer wheel of an * idle CPU then this timer might expire before the next timer event * which is scheduled to wake up that CPU. In case of a completely * idle system the next event might even be infinite time into the * future. wake_up_idle_cpu() ensures that the CPU is woken up and * leaves the inner idle loop so the newly added timer is taken into * account when the CPU goes back to idle and evaluates the timer * wheel for the next timer event. */ static void wake_up_idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); if (cpu == smp_processor_id()) return; if (set_nr_and_not_polling(rq->idle)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); } static bool wake_up_full_nohz_cpu(int cpu) { /* * We just need the target to call irq_exit() and re-evaluate * the next tick. The nohz full kick at least implies that. * If needed we can still optimize that later with an * empty IRQ. */ if (cpu_is_offline(cpu)) return true; /* Don't try to wake offline CPUs. */ if (tick_nohz_full_cpu(cpu)) { if (cpu != smp_processor_id() || tick_nohz_tick_stopped()) tick_nohz_full_kick_cpu(cpu); return true; } return false; } /* * Wake up the specified CPU. If the CPU is going offline, it is the * caller's responsibility to deal with the lost wakeup, for example, * by hooking into the CPU_DEAD notifier like timers and hrtimers do. */ void wake_up_nohz_cpu(int cpu) { if (!wake_up_full_nohz_cpu(cpu)) wake_up_idle_cpu(cpu); } static inline bool got_nohz_idle_kick(void) { int cpu = smp_processor_id(); if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu))) return false; if (idle_cpu(cpu) && !need_resched()) return true; /* * We can't run Idle Load Balance on this CPU for this time so we * cancel it and clear NOHZ_BALANCE_KICK */ clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)); return false; } #else /* CONFIG_NO_HZ_COMMON */ static inline bool got_nohz_idle_kick(void) { return false; } #endif /* CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL bool sched_can_stop_tick(struct rq *rq) { int fifo_nr_running; /* Deadline tasks, even if single, need the tick */ if (rq->dl.dl_nr_running) return false; /* * If there are more than one RR tasks, we need the tick to effect the * actual RR behaviour. */ if (rq->rt.rr_nr_running) { if (rq->rt.rr_nr_running == 1) return true; else return false; } /* * If there's no RR tasks, but FIFO tasks, we can skip the tick, no * forced preemption between FIFO tasks. */ fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running; if (fifo_nr_running) return true; /* * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left; * if there's more than one we need the tick for involuntary * preemption. */ if (rq->nr_running > 1) return false; return true; } #endif /* CONFIG_NO_HZ_FULL */ void sched_avg_update(struct rq *rq) { s64 period = sched_avg_period(); while ((s64)(rq_clock(rq) - rq->age_stamp) > period) { /* * Inline assembly required to prevent the compiler * optimising this loop into a divmod call. * See __iter_div_u64_rem() for another example of this. */ asm("" : "+rm" (rq->age_stamp)); rq->age_stamp += period; rq->rt_avg /= 2; } } #endif /* CONFIG_SMP */ #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH))) /* * Iterate task_group tree rooted at *from, calling @down when first entering a * node and @up when leaving it for the final time. * * Caller must hold rcu_lock or sufficient equivalent. */ int walk_tg_tree_from(struct task_group *from, tg_visitor down, tg_visitor up, void *data) { struct task_group *parent, *child; int ret; parent = from; down: ret = (*down)(parent, data); if (ret) goto out; list_for_each_entry_rcu(child, &parent->children, siblings) { parent = child; goto down; up: continue; } ret = (*up)(parent, data); if (ret || parent == from) goto out; child = parent; parent = parent->parent; if (parent) goto up; out: return ret; } int tg_nop(struct task_group *tg, void *data) { return 0; } #endif static void set_load_weight(struct task_struct *p) { int prio = p->static_prio - MAX_RT_PRIO; struct load_weight *load = &p->se.load; /* * SCHED_IDLE tasks get minimal weight: */ if (idle_policy(p->policy)) { load->weight = scale_load(WEIGHT_IDLEPRIO); load->inv_weight = WMULT_IDLEPRIO; return; } load->weight = scale_load(sched_prio_to_weight[prio]); load->inv_weight = sched_prio_to_wmult[prio]; } static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { update_rq_clock(rq); if (!(flags & ENQUEUE_RESTORE)) sched_info_queued(rq, p); p->sched_class->enqueue_task(rq, p, flags); } static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) { update_rq_clock(rq); if (!(flags & DEQUEUE_SAVE)) sched_info_dequeued(rq, p); p->sched_class->dequeue_task(rq, p, flags); } void activate_task(struct rq *rq, struct task_struct *p, int flags) { if (task_contributes_to_load(p)) rq->nr_uninterruptible--; enqueue_task(rq, p, flags); } void deactivate_task(struct rq *rq, struct task_struct *p, int flags) { if (task_contributes_to_load(p)) rq->nr_uninterruptible++; dequeue_task(rq, p, flags); } static void update_rq_clock_task(struct rq *rq, s64 delta) { /* * In theory, the compile should just see 0 here, and optimize out the call * to sched_rt_avg_update. But I don't trust it... */ #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING) s64 steal = 0, irq_delta = 0; #endif #ifdef CONFIG_IRQ_TIME_ACCOUNTING irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; /* * Since irq_time is only updated on {soft,}irq_exit, we might run into * this case when a previous update_rq_clock() happened inside a * {soft,}irq region. * * When this happens, we stop ->clock_task and only update the * prev_irq_time stamp to account for the part that fit, so that a next * update will consume the rest. This ensures ->clock_task is * monotonic. * * It does however cause some slight miss-attribution of {soft,}irq * time, a more accurate solution would be to update the irq_time using * the current rq->clock timestamp, except that would require using * atomic ops. */ if (irq_delta > delta) irq_delta = delta; rq->prev_irq_time += irq_delta; delta -= irq_delta; #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((¶virt_steal_rq_enabled))) { steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; rq->prev_steal_time_rq += steal; delta -= steal; } #endif rq->clock_task += delta; #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING) if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) sched_rt_avg_update(rq, irq_delta + steal); #endif } void sched_set_stop_task(int cpu, struct task_struct *stop) { struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; struct task_struct *old_stop = cpu_rq(cpu)->stop; if (stop) { /* * Make it appear like a SCHED_FIFO task, its something * userspace knows about and won't get confused about. * * Also, it will make PI more or less work without too * much confusion -- but then, stop work should not * rely on PI working anyway. */ sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m); stop->sched_class = &stop_sched_class; } cpu_rq(cpu)->stop = stop; if (old_stop) { /* * Reset it back to a normal scheduling class so that * it can die in pieces. */ old_stop->sched_class = &rt_sched_class; } } /* * __normal_prio - return the priority that is based on the static prio */ static inline int __normal_prio(struct task_struct *p) { return p->static_prio; } /* * Calculate the expected normal priority: i.e. priority * without taking RT-inheritance into account. Might be * boosted by interactivity modifiers. Changes upon fork, * setprio syscalls, and whenever the interactivity * estimator recalculates. */ static inline int normal_prio(struct task_struct *p) { int prio; if (task_has_dl_policy(p)) prio = MAX_DL_PRIO-1; else if (task_has_rt_policy(p)) prio = MAX_RT_PRIO-1 - p->rt_priority; else prio = __normal_prio(p); return prio; } /* * Calculate the current priority, i.e. the priority * taken into account by the scheduler. This value might * be boosted by RT tasks, or might be boosted by * interactivity modifiers. Will be RT if the task got * RT-boosted. If not then it returns p->normal_prio. */ static int effective_prio(struct task_struct *p) { p->normal_prio = normal_prio(p); /* * If we are RT tasks or we were boosted to RT priority, * keep the priority unchanged. Otherwise, update priority * to the normal priority: */ if (!rt_prio(p->prio)) return p->normal_prio; return p->prio; } /** * task_curr - is this task currently executing on a CPU? * @p: the task in question. * * Return: 1 if the task is currently executing. 0 otherwise. */ inline int task_curr(const struct task_struct *p) { return cpu_curr(task_cpu(p)) == p; } /* * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, * use the balance_callback list if you want balancing. * * this means any call to check_class_changed() must be followed by a call to * balance_callback(). */ static inline void check_class_changed(struct rq *rq, struct task_struct *p, const struct sched_class *prev_class, int oldprio) { if (prev_class != p->sched_class) { if (prev_class->switched_from) prev_class->switched_from(rq, p); p->sched_class->switched_to(rq, p); } else if (oldprio != p->prio || dl_task(p)) p->sched_class->prio_changed(rq, p, oldprio); } void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) { const struct sched_class *class; if (p->sched_class == rq->curr->sched_class) { rq->curr->sched_class->check_preempt_curr(rq, p, flags); } else { for_each_class(class) { if (class == rq->curr->sched_class) break; if (class == p->sched_class) { resched_curr(rq); break; } } } /* * A queue event has occurred, and we're going to schedule. In * this case, we can save a useless back to back clock update. */ if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) rq_clock_skip_update(rq, true); } #ifdef CONFIG_SMP /* * This is how migration works: * * 1) we invoke migration_cpu_stop() on the target CPU using * stop_one_cpu(). * 2) stopper starts to run (implicitly forcing the migrated thread * off the CPU) * 3) it checks whether the migrated task is still in the wrong runqueue. * 4) if it's in the wrong runqueue then the migration thread removes * it and puts it into the right queue. * 5) stopper completes and stop_one_cpu() returns and the migration * is done. */ /* * move_queued_task - move a queued task to new rq. * * Returns (locked) new rq. Old rq's lock is released. */ static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new_cpu) { lockdep_assert_held(&rq->lock); p->on_rq = TASK_ON_RQ_MIGRATING; dequeue_task(rq, p, 0); set_task_cpu(p, new_cpu); raw_spin_unlock(&rq->lock); rq = cpu_rq(new_cpu); raw_spin_lock(&rq->lock); BUG_ON(task_cpu(p) != new_cpu); enqueue_task(rq, p, 0); p->on_rq = TASK_ON_RQ_QUEUED; check_preempt_curr(rq, p, 0); return rq; } struct migration_arg { struct task_struct *task; int dest_cpu; }; /* * Move (not current) task off this cpu, onto dest cpu. We're doing * this because either it can't run here any more (set_cpus_allowed() * away from this CPU, or CPU going down), or because we're * attempting to rebalance this task on exec (sched_exec). * * So we race with normal scheduler movements, but that's OK, as long * as the task is no longer on this CPU. */ static struct rq *__migrate_task(struct rq *rq, struct task_struct *p, int dest_cpu) { if (unlikely(!cpu_active(dest_cpu))) return rq; /* Affinity changed (again). */ if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) return rq; rq = move_queued_task(rq, p, dest_cpu); return rq; } /* * migration_cpu_stop - this will be executed by a highprio stopper thread * and performs thread migration by bumping thread off CPU then * 'pushing' onto another runqueue. */ static int migration_cpu_stop(void *data) { struct migration_arg *arg = data; struct task_struct *p = arg->task; struct rq *rq = this_rq(); /* * The original target cpu might have gone down and we might * be on another cpu but it doesn't matter. */ local_irq_disable(); /* * We need to explicitly wake pending tasks before running * __migrate_task() such that we will not miss enforcing cpus_allowed * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. */ sched_ttwu_pending(); raw_spin_lock(&p->pi_lock); raw_spin_lock(&rq->lock); /* * If task_rq(p) != rq, it cannot be migrated here, because we're * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because * we're holding p->pi_lock. */ if (task_rq(p) == rq) { if (task_on_rq_queued(p)) rq = __migrate_task(rq, p, arg->dest_cpu); else p->wake_cpu = arg->dest_cpu; } raw_spin_unlock(&rq->lock); raw_spin_unlock(&p->pi_lock); local_irq_enable(); return 0; } /* * sched_class::set_cpus_allowed must do the below, but is not required to * actually call this function. */ void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask) { cpumask_copy(&p->cpus_allowed, new_mask); p->nr_cpus_allowed = cpumask_weight(new_mask); } void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) { struct rq *rq = task_rq(p); bool queued, running; lockdep_assert_held(&p->pi_lock); queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) { /* * Because __kthread_bind() calls this on blocked tasks without * holding rq->lock. */ lockdep_assert_held(&rq->lock); dequeue_task(rq, p, DEQUEUE_SAVE); } if (running) put_prev_task(rq, p); p->sched_class->set_cpus_allowed(p, new_mask); if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE); if (running) set_curr_task(rq, p); } /* * Change a given task's CPU affinity. Migrate the thread to a * proper CPU and schedule it away if the CPU it's executing on * is removed from the allowed bitmask. * * NOTE: the caller must have a valid reference to the task, the * task must not exit() & deallocate itself prematurely. The * call is not atomic; no spinlocks may be held. */ static int __set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask, bool check) { const struct cpumask *cpu_valid_mask = cpu_active_mask; unsigned int dest_cpu; struct rq_flags rf; struct rq *rq; int ret = 0; rq = task_rq_lock(p, &rf); if (p->flags & PF_KTHREAD) { /* * Kernel threads are allowed on online && !active CPUs */ cpu_valid_mask = cpu_online_mask; } /* * Must re-check here, to close a race against __kthread_bind(), * sched_setaffinity() is not guaranteed to observe the flag. */ if (check && (p->flags & PF_NO_SETAFFINITY)) { ret = -EINVAL; goto out; } if (cpumask_equal(&p->cpus_allowed, new_mask)) goto out; if (!cpumask_intersects(new_mask, cpu_valid_mask)) { ret = -EINVAL; goto out; } do_set_cpus_allowed(p, new_mask); if (p->flags & PF_KTHREAD) { /* * For kernel threads that do indeed end up on online && * !active we want to ensure they are strict per-cpu threads. */ WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) && !cpumask_intersects(new_mask, cpu_active_mask) && p->nr_cpus_allowed != 1); } /* Can the task run on the task's current CPU? If so, we're done */ if (cpumask_test_cpu(task_cpu(p), new_mask)) goto out; dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); if (task_running(rq, p) || p->state == TASK_WAKING) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ task_rq_unlock(rq, p, &rf); stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); tlb_migrate_finish(p->mm); return 0; } else if (task_on_rq_queued(p)) { /* * OK, since we're going to drop the lock immediately * afterwards anyway. */ lockdep_unpin_lock(&rq->lock, rf.cookie); rq = move_queued_task(rq, p, dest_cpu); lockdep_repin_lock(&rq->lock, rf.cookie); } out: task_rq_unlock(rq, p, &rf); return ret; } int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) { return __set_cpus_allowed_ptr(p, new_mask, false); } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); void set_task_cpu(struct task_struct *p, unsigned int new_cpu) { #ifdef CONFIG_SCHED_DEBUG /* * We should never call set_task_cpu() on a blocked task, * ttwu() will sort out the placement. */ WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING && !p->on_rq); /* * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING, * because schedstat_wait_{start,end} rebase migrating task's wait_start * time relying on p->on_rq. */ WARN_ON_ONCE(p->state == TASK_RUNNING && p->sched_class == &fair_sched_class && (p->on_rq && !task_on_rq_migrating(p))); #ifdef CONFIG_LOCKDEP /* * The caller should hold either p->pi_lock or rq->lock, when changing * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks. * * sched_move_task() holds both and thus holding either pins the cgroup, * see task_group(). * * Furthermore, all task_rq users should acquire both locks, see * task_rq_lock(). */ WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || lockdep_is_held(&task_rq(p)->lock))); #endif #endif trace_sched_migrate_task(p, new_cpu); if (task_cpu(p) != new_cpu) { if (p->sched_class->migrate_task_rq) p->sched_class->migrate_task_rq(p); p->se.nr_migrations++; perf_event_task_migrate(p); } __set_task_cpu(p, new_cpu); } static void __migrate_swap_task(struct task_struct *p, int cpu) { if (task_on_rq_queued(p)) { struct rq *src_rq, *dst_rq; src_rq = task_rq(p); dst_rq = cpu_rq(cpu); p->on_rq = TASK_ON_RQ_MIGRATING; deactivate_task(src_rq, p, 0); set_task_cpu(p, cpu); activate_task(dst_rq, p, 0); p->on_rq = TASK_ON_RQ_QUEUED; check_preempt_curr(dst_rq, p, 0); } else { /* * Task isn't running anymore; make it appear like we migrated * it before it went to sleep. This means on wakeup we make the * previous cpu our target instead of where it really is. */ p->wake_cpu = cpu; } } struct migration_swap_arg { struct task_struct *src_task, *dst_task; int src_cpu, dst_cpu; }; static int migrate_swap_stop(void *data) { struct migration_swap_arg *arg = data; struct rq *src_rq, *dst_rq; int ret = -EAGAIN; if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu)) return -EAGAIN; src_rq = cpu_rq(arg->src_cpu); dst_rq = cpu_rq(arg->dst_cpu); double_raw_lock(&arg->src_task->pi_lock, &arg->dst_task->pi_lock); double_rq_lock(src_rq, dst_rq); if (task_cpu(arg->dst_task) != arg->dst_cpu) goto unlock; if (task_cpu(arg->src_task) != arg->src_cpu) goto unlock; if (!cpumask_test_cpu(arg->dst_cpu, tsk_cpus_allowed(arg->src_task))) goto unlock; if (!cpumask_test_cpu(arg->src_cpu, tsk_cpus_allowed(arg->dst_task))) goto unlock; __migrate_swap_task(arg->src_task, arg->dst_cpu); __migrate_swap_task(arg->dst_task, arg->src_cpu); ret = 0; unlock: double_rq_unlock(src_rq, dst_rq); raw_spin_unlock(&arg->dst_task->pi_lock); raw_spin_unlock(&arg->src_task->pi_lock); return ret; } /* * Cross migrate two tasks */ int migrate_swap(struct task_struct *cur, struct task_struct *p) { struct migration_swap_arg arg; int ret = -EINVAL; arg = (struct migration_swap_arg){ .src_task = cur, .src_cpu = task_cpu(cur), .dst_task = p, .dst_cpu = task_cpu(p), }; if (arg.src_cpu == arg.dst_cpu) goto out; /* * These three tests are all lockless; this is OK since all of them * will be re-checked with proper locks held further down the line. */ if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu)) goto out; if (!cpumask_test_cpu(arg.dst_cpu, tsk_cpus_allowed(arg.src_task))) goto out; if (!cpumask_test_cpu(arg.src_cpu, tsk_cpus_allowed(arg.dst_task))) goto out; trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu); ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg); out: return ret; } /* * wait_task_inactive - wait for a thread to unschedule. * * If @match_state is nonzero, it's the @p->state value just checked and * not expected to change. If it changes, i.e. @p might have woken up, * then return zero. When we succeed in waiting for @p to be off its CPU, * we return a positive number (its total switch count). If a second call * a short while later returns the same number, the caller can be sure that * @p has remained unscheduled the whole time. * * The caller must ensure that the task *will* unschedule sometime soon, * else this function might spin for a *long* time. This function can't * be called with interrupts off, or it may introduce deadlock with * smp_call_function() if an IPI is sent by the same process we are * waiting to become inactive. */ unsigned long wait_task_inactive(struct task_struct *p, long match_state) { int running, queued; struct rq_flags rf; unsigned long ncsw; struct rq *rq; for (;;) { /* * We do the initial early heuristics without holding * any task-queue locks at all. We'll only try to get * the runqueue lock when things look like they will * work out! */ rq = task_rq(p); /* * If the task is actively running on another CPU * still, just relax and busy-wait without holding * any locks. * * NOTE! Since we don't hold any locks, it's not * even sure that "rq" stays as the right runqueue! * But we don't care, since "task_running()" will * return false if the runqueue has changed and p * is actually now running somewhere else! */ while (task_running(rq, p)) { if (match_state && unlikely(p->state != match_state)) return 0; cpu_relax(); } /* * Ok, time to look more closely! We need the rq * lock now, to be *sure*. If we're wrong, we'll * just go back and repeat. */ rq = task_rq_lock(p, &rf); trace_sched_wait_task(p); running = task_running(rq, p); queued = task_on_rq_queued(p); ncsw = 0; if (!match_state || p->state == match_state) ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ task_rq_unlock(rq, p, &rf); /* * If it changed from the expected state, bail out now. */ if (unlikely(!ncsw)) break; /* * Was it really running after all now that we * checked with the proper locks actually held? * * Oops. Go back and try again.. */ if (unlikely(running)) { cpu_relax(); continue; } /* * It's not enough that it's not actively running, * it must be off the runqueue _entirely_, and not * preempted! * * So if it was still runnable (but just not actively * running right now), it's preempted, and we should * yield - it could be a while. */ if (unlikely(queued)) { ktime_t to = ktime_set(0, NSEC_PER_SEC/HZ); set_current_state(TASK_UNINTERRUPTIBLE); schedule_hrtimeout(&to, HRTIMER_MODE_REL); continue; } /* * Ahh, all good. It wasn't running, and it wasn't * runnable, which means that it will never become * running in the future either. We're all done! */ break; } return ncsw; } /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread * * Cause a process which is running on another CPU to enter * kernel-mode, without any delay. (to get signals handled.) * * NOTE: this function doesn't have to take the runqueue lock, * because all it wants to ensure is that the remote task enters * the kernel. If the IPI races and the task has been migrated * to another CPU then no harm is done and the purpose has been * achieved as well. */ void kick_process(struct task_struct *p) { int cpu; preempt_disable(); cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); preempt_enable(); } EXPORT_SYMBOL_GPL(kick_process); /* * ->cpus_allowed is protected by both rq->lock and p->pi_lock * * A few notes on cpu_active vs cpu_online: * * - cpu_active must be a subset of cpu_online * * - on cpu-up we allow per-cpu kthreads on the online && !active cpu, * see __set_cpus_allowed_ptr(). At this point the newly online * cpu isn't yet part of the sched domains, and balancing will not * see it. * * - on cpu-down we clear cpu_active() to mask the sched domains and * avoid the load balancer to place new tasks on the to be removed * cpu. Existing tasks will remain running there and will be taken * off. * * This means that fallback selection must not select !active CPUs. * And can assume that any active CPU must be online. Conversely * select_task_rq() below may allow selection of !active CPUs in order * to satisfy the above rules. */ static int select_fallback_rq(int cpu, struct task_struct *p) { int nid = cpu_to_node(cpu); const struct cpumask *nodemask = NULL; enum { cpuset, possible, fail } state = cpuset; int dest_cpu; /* * If the node that the cpu is on has been offlined, cpu_to_node() * will return -1. There is no cpu on the node, and we should * select the cpu on the other node. */ if (nid != -1) { nodemask = cpumask_of_node(nid); /* Look for allowed, online CPU in same node. */ for_each_cpu(dest_cpu, nodemask) { if (!cpu_active(dest_cpu)) continue; if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) return dest_cpu; } } for (;;) { /* Any allowed, online CPU? */ for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) { if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu)) continue; if (!cpu_online(dest_cpu)) continue; goto out; } /* No more Mr. Nice Guy. */ switch (state) { case cpuset: if (IS_ENABLED(CONFIG_CPUSETS)) { cpuset_cpus_allowed_fallback(p); state = possible; break; } /* fall-through */ case possible: do_set_cpus_allowed(p, cpu_possible_mask); state = fail; break; case fail: BUG(); break; } } out: if (state != cpuset) { /* * Don't tell them about moving exiting tasks or * kernel threads (both mm NULL), since they never * leave kernel. */ if (p->mm && printk_ratelimit()) { printk_deferred("process %d (%s) no longer affine to cpu%d\n", task_pid_nr(p), p->comm, cpu); } } return dest_cpu; } /* * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable. */ static inline int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags) { lockdep_assert_held(&p->pi_lock); if (tsk_nr_cpus_allowed(p) > 1) cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags); else cpu = cpumask_any(tsk_cpus_allowed(p)); /* * In order not to call set_task_cpu() on a blocking task we need * to rely on ttwu() to place the task on a valid ->cpus_allowed * cpu. * * Since this is common to all placement strategies, this lives here. * * [ this allows ->select_task() to simply return task_cpu(p) and * not worry about this generic constraint ] */ if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) || !cpu_online(cpu))) cpu = select_fallback_rq(task_cpu(p), p); return cpu; } static void update_avg(u64 *avg, u64 sample) { s64 diff = sample - *avg; *avg += diff >> 3; } #else static inline int __set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask, bool check) { return set_cpus_allowed_ptr(p, new_mask); } #endif /* CONFIG_SMP */ static void ttwu_stat(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq; if (!schedstat_enabled()) return; rq = this_rq(); #ifdef CONFIG_SMP if (cpu == rq->cpu) { schedstat_inc(rq->ttwu_local); schedstat_inc(p->se.statistics.nr_wakeups_local); } else { struct sched_domain *sd; schedstat_inc(p->se.statistics.nr_wakeups_remote); rcu_read_lock(); for_each_domain(rq->cpu, sd) { if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { schedstat_inc(sd->ttwu_wake_remote); break; } } rcu_read_unlock(); } if (wake_flags & WF_MIGRATED) schedstat_inc(p->se.statistics.nr_wakeups_migrate); #endif /* CONFIG_SMP */ schedstat_inc(rq->ttwu_count); schedstat_inc(p->se.statistics.nr_wakeups); if (wake_flags & WF_SYNC) schedstat_inc(p->se.statistics.nr_wakeups_sync); } static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags) { activate_task(rq, p, en_flags); p->on_rq = TASK_ON_RQ_QUEUED; /* if a worker is waking up, notify workqueue */ if (p->flags & PF_WQ_WORKER) wq_worker_waking_up(p, cpu_of(rq)); } /* * Mark the task runnable and perform wakeup-preemption. */ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags, struct pin_cookie cookie) { check_preempt_curr(rq, p, wake_flags); p->state = TASK_RUNNING; trace_sched_wakeup(p); #ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* * Our task @p is fully woken up and running; so its safe to * drop the rq->lock, hereafter rq is only used for statistics. */ lockdep_unpin_lock(&rq->lock, cookie); p->sched_class->task_woken(rq, p); lockdep_repin_lock(&rq->lock, cookie); } if (rq->idle_stamp) { u64 delta = rq_clock(rq) - rq->idle_stamp; u64 max = 2*rq->max_idle_balance_cost; update_avg(&rq->avg_idle, delta); if (rq->avg_idle > max) rq->avg_idle = max; rq->idle_stamp = 0; } #endif } static void ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, struct pin_cookie cookie) { int en_flags = ENQUEUE_WAKEUP; lockdep_assert_held(&rq->lock); #ifdef CONFIG_SMP if (p->sched_contributes_to_load) rq->nr_uninterruptible--; if (wake_flags & WF_MIGRATED) en_flags |= ENQUEUE_MIGRATED; #endif ttwu_activate(rq, p, en_flags); ttwu_do_wakeup(rq, p, wake_flags, cookie); } /* * Called in case the task @p isn't fully descheduled from its runqueue, * in this case we must do a remote wakeup. Its a 'light' wakeup though, * since all we need to do is flip p->state to TASK_RUNNING, since * the task is still ->on_rq. */ static int ttwu_remote(struct task_struct *p, int wake_flags) { struct rq_flags rf; struct rq *rq; int ret = 0; rq = __task_rq_lock(p, &rf); if (task_on_rq_queued(p)) { /* check_preempt_curr() may use rq clock */ update_rq_clock(rq); ttwu_do_wakeup(rq, p, wake_flags, rf.cookie); ret = 1; } __task_rq_unlock(rq, &rf); return ret; } #ifdef CONFIG_SMP void sched_ttwu_pending(void) { struct rq *rq = this_rq(); struct llist_node *llist = llist_del_all(&rq->wake_list); struct pin_cookie cookie; struct task_struct *p; unsigned long flags; if (!llist) return; raw_spin_lock_irqsave(&rq->lock, flags); cookie = lockdep_pin_lock(&rq->lock); while (llist) { int wake_flags = 0; p = llist_entry(llist, struct task_struct, wake_entry); llist = llist_next(llist); if (p->sched_remote_wakeup) wake_flags = WF_MIGRATED; ttwu_do_activate(rq, p, wake_flags, cookie); } lockdep_unpin_lock(&rq->lock, cookie); raw_spin_unlock_irqrestore(&rq->lock, flags); } void scheduler_ipi(void) { /* * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting * TIF_NEED_RESCHED remotely (for the first time) will also send * this IPI. */ preempt_fold_need_resched(); if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) return; /* * Not all reschedule IPI handlers call irq_enter/irq_exit, since * traditionally all their work was done from the interrupt return * path. Now that we actually do some work, we need to make sure * we do call them. * * Some archs already do call them, luckily irq_enter/exit nest * properly. * * Arguably we should visit all archs and update all handlers, * however a fair share of IPIs are still resched only so this would * somewhat pessimize the simple resched case. */ irq_enter(); sched_ttwu_pending(); /* * Check if someone kicked us for doing the nohz idle load balance. */ if (unlikely(got_nohz_idle_kick())) { this_rq()->idle_balance = 1; raise_softirq_irqoff(SCHED_SOFTIRQ); } irq_exit(); } static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) { if (!set_nr_if_polling(rq->idle)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); } } void wake_up_if_idle(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; rcu_read_lock(); if (!is_idle_task(rcu_dereference(rq->curr))) goto out; if (set_nr_if_polling(rq->idle)) { trace_sched_wake_idle_without_ipi(cpu); } else { raw_spin_lock_irqsave(&rq->lock, flags); if (is_idle_task(rq->curr)) smp_send_reschedule(cpu); /* Else cpu is not in idle, do nothing here */ raw_spin_unlock_irqrestore(&rq->lock, flags); } out: rcu_read_unlock(); } bool cpus_share_cache(int this_cpu, int that_cpu) { return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); } #endif /* CONFIG_SMP */ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); struct pin_cookie cookie; #if defined(CONFIG_SMP) if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) { sched_clock_cpu(cpu); /* sync clocks x-cpu */ ttwu_queue_remote(p, cpu, wake_flags); return; } #endif raw_spin_lock(&rq->lock); cookie = lockdep_pin_lock(&rq->lock); ttwu_do_activate(rq, p, wake_flags, cookie); lockdep_unpin_lock(&rq->lock, cookie); raw_spin_unlock(&rq->lock); } /* * Notes on Program-Order guarantees on SMP systems. * * MIGRATION * * The basic program-order guarantee on SMP systems is that when a task [t] * migrates, all its activity on its old cpu [c0] happens-before any subsequent * execution on its new cpu [c1]. * * For migration (of runnable tasks) this is provided by the following means: * * A) UNLOCK of the rq(c0)->lock scheduling out task t * B) migration for t is required to synchronize *both* rq(c0)->lock and * rq(c1)->lock (if not at the same time, then in that order). * C) LOCK of the rq(c1)->lock scheduling in task * * Transitivity guarantees that B happens after A and C after B. * Note: we only require RCpc transitivity. * Note: the cpu doing B need not be c0 or c1 * * Example: * * CPU0 CPU1 CPU2 * * LOCK rq(0)->lock * sched-out X * sched-in Y * UNLOCK rq(0)->lock * * LOCK rq(0)->lock // orders against CPU0 * dequeue X * UNLOCK rq(0)->lock * * LOCK rq(1)->lock * enqueue X * UNLOCK rq(1)->lock * * LOCK rq(1)->lock // orders against CPU2 * sched-out Z * sched-in X * UNLOCK rq(1)->lock * * * BLOCKING -- aka. SLEEP + WAKEUP * * For blocking we (obviously) need to provide the same guarantee as for * migration. However the means are completely different as there is no lock * chain to provide order. Instead we do: * * 1) smp_store_release(X->on_cpu, 0) * 2) smp_cond_load_acquire(!X->on_cpu) * * Example: * * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule) * * LOCK rq(0)->lock LOCK X->pi_lock * dequeue X * sched-out X * smp_store_release(X->on_cpu, 0); * * smp_cond_load_acquire(&X->on_cpu, !VAL); * X->state = WAKING * set_task_cpu(X,2) * * LOCK rq(2)->lock * enqueue X * X->state = RUNNING * UNLOCK rq(2)->lock * * LOCK rq(2)->lock // orders against CPU1 * sched-out Z * sched-in X * UNLOCK rq(2)->lock * * UNLOCK X->pi_lock * UNLOCK rq(0)->lock * * * However; for wakeups there is a second guarantee we must provide, namely we * must observe the state that lead to our wakeup. That is, not only must our * task observe its own prior state, it must also observe the stores prior to * its wakeup. * * This means that any means of doing remote wakeups must order the CPU doing * the wakeup against the CPU the task is going to end up running on. This, * however, is already required for the regular Program-Order guarantee above, * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire). * */ /** * try_to_wake_up - wake up a thread * @p: the thread to be awakened * @state: the mask of task states that can be woken * @wake_flags: wake modifier flags (WF_*) * * If (@state & @p->state) @p->state = TASK_RUNNING. * * If the task was not queued/runnable, also place it back on a runqueue. * * Atomic against schedule() which would dequeue a task, also see * set_current_state(). * * Return: %true if @p->state changes (an actual wakeup was done), * %false otherwise. */ static int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) { unsigned long flags; int cpu, success = 0; /* * If we are going to wake up a thread waiting for CONDITION we * need to ensure that CONDITION=1 done by the caller can not be * reordered with p->state check below. This pairs with mb() in * set_current_state() the waiting thread does. */ smp_mb__before_spinlock(); raw_spin_lock_irqsave(&p->pi_lock, flags); if (!(p->state & state)) goto out; trace_sched_waking(p); success = 1; /* we're going to change ->state */ cpu = task_cpu(p); /* * Ensure we load p->on_rq _after_ p->state, otherwise it would * be possible to, falsely, observe p->on_rq == 0 and get stuck * in smp_cond_load_acquire() below. * * sched_ttwu_pending() try_to_wake_up() * [S] p->on_rq = 1; [L] P->state * UNLOCK rq->lock -----. * \ * +--- RMB * schedule() / * LOCK rq->lock -----' * UNLOCK rq->lock * * [task p] * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq * * Pairs with the UNLOCK+LOCK on rq->lock from the * last wakeup of our task and the schedule that got our task * current. */ smp_rmb(); if (p->on_rq && ttwu_remote(p, wake_flags)) goto stat; #ifdef CONFIG_SMP /* * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be * possible to, falsely, observe p->on_cpu == 0. * * One must be running (->on_cpu == 1) in order to remove oneself * from the runqueue. * * [S] ->on_cpu = 1; [L] ->on_rq * UNLOCK rq->lock * RMB * LOCK rq->lock * [S] ->on_rq = 0; [L] ->on_cpu * * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock * from the consecutive calls to schedule(); the first switching to our * task, the second putting it to sleep. */ smp_rmb(); /* * If the owning (remote) cpu is still in the middle of schedule() with * this task as prev, wait until its done referencing the task. * * Pairs with the smp_store_release() in finish_lock_switch(). * * This ensures that tasks getting woken will be fully ordered against * their previous state and preserve Program Order. */ smp_cond_load_acquire(&p->on_cpu, !VAL); p->sched_contributes_to_load = !!task_contributes_to_load(p); p->state = TASK_WAKING; cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags); if (task_cpu(p) != cpu) { wake_flags |= WF_MIGRATED; set_task_cpu(p, cpu); } #endif /* CONFIG_SMP */ ttwu_queue(p, cpu, wake_flags); stat: ttwu_stat(p, cpu, wake_flags); out: raw_spin_unlock_irqrestore(&p->pi_lock, flags); return success; } /** * try_to_wake_up_local - try to wake up a local task with rq lock held * @p: the thread to be awakened * @cookie: context's cookie for pinning * * Put @p on the run-queue if it's not already there. The caller must * ensure that this_rq() is locked, @p is bound to this_rq() and not * the current task. */ static void try_to_wake_up_local(struct task_struct *p, struct pin_cookie cookie) { struct rq *rq = task_rq(p); if (WARN_ON_ONCE(rq != this_rq()) || WARN_ON_ONCE(p == current)) return; lockdep_assert_held(&rq->lock); if (!raw_spin_trylock(&p->pi_lock)) { /* * This is OK, because current is on_cpu, which avoids it being * picked for load-balance and preemption/IRQs are still * disabled avoiding further scheduler activity on it and we've * not yet picked a replacement task. */ lockdep_unpin_lock(&rq->lock, cookie); raw_spin_unlock(&rq->lock); raw_spin_lock(&p->pi_lock); raw_spin_lock(&rq->lock); lockdep_repin_lock(&rq->lock, cookie); } if (!(p->state & TASK_NORMAL)) goto out; trace_sched_waking(p); if (!task_on_rq_queued(p)) ttwu_activate(rq, p, ENQUEUE_WAKEUP); ttwu_do_wakeup(rq, p, 0, cookie); ttwu_stat(p, smp_processor_id(), 0); out: raw_spin_unlock(&p->pi_lock); } /** * wake_up_process - Wake up a specific process * @p: The process to be woken up. * * Attempt to wake up the nominated process and move it to the set of runnable * processes. * * Return: 1 if the process was woken up, 0 if it was already running. * * It may be assumed that this function implies a write memory barrier before * changing the task state if and only if any tasks are woken up. */ int wake_up_process(struct task_struct *p) { return try_to_wake_up(p, TASK_NORMAL, 0); } EXPORT_SYMBOL(wake_up_process); int wake_up_state(struct task_struct *p, unsigned int state) { return try_to_wake_up(p, state, 0); } /* * This function clears the sched_dl_entity static params. */ void __dl_clear_params(struct task_struct *p) { struct sched_dl_entity *dl_se = &p->dl; dl_se->dl_runtime = 0; dl_se->dl_deadline = 0; dl_se->dl_period = 0; dl_se->flags = 0; dl_se->dl_bw = 0; dl_se->dl_throttled = 0; dl_se->dl_yielded = 0; } /* * Perform scheduler related setup for a newly forked process p. * p is forked by current. * * __sched_fork() is basic setup used by init_idle() too: */ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) { p->on_rq = 0; p->se.on_rq = 0; p->se.exec_start = 0; p->se.sum_exec_runtime = 0; p->se.prev_sum_exec_runtime = 0; p->se.nr_migrations = 0; p->se.vruntime = 0; INIT_LIST_HEAD(&p->se.group_node); #ifdef CONFIG_FAIR_GROUP_SCHED p->se.cfs_rq = NULL; #endif #ifdef CONFIG_SCHEDSTATS /* Even if schedstat is disabled, there should not be garbage */ memset(&p->se.statistics, 0, sizeof(p->se.statistics)); #endif RB_CLEAR_NODE(&p->dl.rb_node); init_dl_task_timer(&p->dl); __dl_clear_params(p); INIT_LIST_HEAD(&p->rt.run_list); p->rt.timeout = 0; p->rt.time_slice = sched_rr_timeslice; p->rt.on_rq = 0; p->rt.on_list = 0; #ifdef CONFIG_PREEMPT_NOTIFIERS INIT_HLIST_HEAD(&p->preempt_notifiers); #endif #ifdef CONFIG_NUMA_BALANCING if (p->mm && atomic_read(&p->mm->mm_users) == 1) { p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); p->mm->numa_scan_seq = 0; } if (clone_flags & CLONE_VM) p->numa_preferred_nid = current->numa_preferred_nid; else p->numa_preferred_nid = -1; p->node_stamp = 0ULL; p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0; p->numa_scan_period = sysctl_numa_balancing_scan_delay; p->numa_work.next = &p->numa_work; p->numa_faults = NULL; p->last_task_numa_placement = 0; p->last_sum_exec_runtime = 0; p->numa_group = NULL; #endif /* CONFIG_NUMA_BALANCING */ } DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); #ifdef CONFIG_NUMA_BALANCING void set_numabalancing_state(bool enabled) { if (enabled) static_branch_enable(&sched_numa_balancing); else static_branch_disable(&sched_numa_balancing); } #ifdef CONFIG_PROC_SYSCTL int sysctl_numa_balancing(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; int state = static_branch_likely(&sched_numa_balancing); if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &state; err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) set_numabalancing_state(state); return err; } #endif #endif #ifdef CONFIG_SCHEDSTATS DEFINE_STATIC_KEY_FALSE(sched_schedstats); static bool __initdata __sched_schedstats = false; static void set_schedstats(bool enabled) { if (enabled) static_branch_enable(&sched_schedstats); else static_branch_disable(&sched_schedstats); } void force_schedstat_enabled(void) { if (!schedstat_enabled()) { pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n"); static_branch_enable(&sched_schedstats); } } static int __init setup_schedstats(char *str) { int ret = 0; if (!str) goto out; /* * This code is called before jump labels have been set up, so we can't * change the static branch directly just yet. Instead set a temporary * variable so init_schedstats() can do it later. */ if (!strcmp(str, "enable")) { __sched_schedstats = true; ret = 1; } else if (!strcmp(str, "disable")) { __sched_schedstats = false; ret = 1; } out: if (!ret) pr_warn("Unable to parse schedstats=\n"); return ret; } __setup("schedstats=", setup_schedstats); static void __init init_schedstats(void) { set_schedstats(__sched_schedstats); } #ifdef CONFIG_PROC_SYSCTL int sysctl_schedstats(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; int state = static_branch_likely(&sched_schedstats); if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &state; err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) set_schedstats(state); return err; } #endif /* CONFIG_PROC_SYSCTL */ #else /* !CONFIG_SCHEDSTATS */ static inline void init_schedstats(void) {} #endif /* CONFIG_SCHEDSTATS */ /* * fork()/clone()-time setup: */ int sched_fork(unsigned long clone_flags, struct task_struct *p) { unsigned long flags; int cpu = get_cpu(); __sched_fork(clone_flags, p); /* * We mark the process as NEW here. This guarantees that * nobody will actually run it, and a signal or other external * event cannot wake it up and insert it on the runqueue either. */ p->state = TASK_NEW; /* * Make sure we do not leak PI boosting priority to the child. */ p->prio = current->normal_prio; /* * Revert to default priority/policy on fork if requested. */ if (unlikely(p->sched_reset_on_fork)) { if (task_has_dl_policy(p) || task_has_rt_policy(p)) { p->policy = SCHED_NORMAL; p->static_prio = NICE_TO_PRIO(0); p->rt_priority = 0; } else if (PRIO_TO_NICE(p->static_prio) < 0) p->static_prio = NICE_TO_PRIO(0); p->prio = p->normal_prio = __normal_prio(p); set_load_weight(p); /* * We don't need the reset flag anymore after the fork. It has * fulfilled its duty: */ p->sched_reset_on_fork = 0; } if (dl_prio(p->prio)) { put_cpu(); return -EAGAIN; } else if (rt_prio(p->prio)) { p->sched_class = &rt_sched_class; } else { p->sched_class = &fair_sched_class; } init_entity_runnable_average(&p->se); /* * The child is not yet in the pid-hash so no cgroup attach races, * and the cgroup is pinned to this child due to cgroup_fork() * is ran before sched_fork(). * * Silence PROVE_RCU. */ raw_spin_lock_irqsave(&p->pi_lock, flags); /* * We're setting the cpu for the first time, we don't migrate, * so use __set_task_cpu(). */ __set_task_cpu(p, cpu); if (p->sched_class->task_fork) p->sched_class->task_fork(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); #ifdef CONFIG_SCHED_INFO if (likely(sched_info_on())) memset(&p->sched_info, 0, sizeof(p->sched_info)); #endif #if defined(CONFIG_SMP) p->on_cpu = 0; #endif init_task_preempt_count(p); #ifdef CONFIG_SMP plist_node_init(&p->pushable_tasks, MAX_PRIO); RB_CLEAR_NODE(&p->pushable_dl_tasks); #endif put_cpu(); return 0; } unsigned long to_ratio(u64 period, u64 runtime) { if (runtime == RUNTIME_INF) return 1ULL << 20; /* * Doing this here saves a lot of checks in all * the calling paths, and returning zero seems * safe for them anyway. */ if (period == 0) return 0; return div64_u64(runtime << 20, period); } #ifdef CONFIG_SMP inline struct dl_bw *dl_bw_of(int i) { RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(), "sched RCU must be held"); return &cpu_rq(i)->rd->dl_bw; } static inline int dl_bw_cpus(int i) { struct root_domain *rd = cpu_rq(i)->rd; int cpus = 0; RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(), "sched RCU must be held"); for_each_cpu_and(i, rd->span, cpu_active_mask) cpus++; return cpus; } #else inline struct dl_bw *dl_bw_of(int i) { return &cpu_rq(i)->dl.dl_bw; } static inline int dl_bw_cpus(int i) { return 1; } #endif /* * We must be sure that accepting a new task (or allowing changing the * parameters of an existing one) is consistent with the bandwidth * constraints. If yes, this function also accordingly updates the currently * allocated bandwidth to reflect the new situation. * * This function is called while holding p's rq->lock. * * XXX we should delay bw change until the task's 0-lag point, see * __setparam_dl(). */ static int dl_overflow(struct task_struct *p, int policy, const struct sched_attr *attr) { struct dl_bw *dl_b = dl_bw_of(task_cpu(p)); u64 period = attr->sched_period ?: attr->sched_deadline; u64 runtime = attr->sched_runtime; u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0; int cpus, err = -1; /* !deadline task may carry old deadline bandwidth */ if (new_bw == p->dl.dl_bw && task_has_dl_policy(p)) return 0; /* * Either if a task, enters, leave, or stays -deadline but changes * its parameters, we may need to update accordingly the total * allocated bandwidth of the container. */ raw_spin_lock(&dl_b->lock); cpus = dl_bw_cpus(task_cpu(p)); if (dl_policy(policy) && !task_has_dl_policy(p) && !__dl_overflow(dl_b, cpus, 0, new_bw)) { __dl_add(dl_b, new_bw); err = 0; } else if (dl_policy(policy) && task_has_dl_policy(p) && !__dl_overflow(dl_b, cpus, p->dl.dl_bw, new_bw)) { __dl_clear(dl_b, p->dl.dl_bw); __dl_add(dl_b, new_bw); err = 0; } else if (!dl_policy(policy) && task_has_dl_policy(p)) { __dl_clear(dl_b, p->dl.dl_bw); err = 0; } raw_spin_unlock(&dl_b->lock); return err; } extern void init_dl_bw(struct dl_bw *dl_b); /* * wake_up_new_task - wake up a newly created task for the first time. * * This function will do some initial scheduler statistics housekeeping * that must be done for every newly created context, then puts the task * on the runqueue and wakes it. */ void wake_up_new_task(struct task_struct *p) { struct rq_flags rf; struct rq *rq; raw_spin_lock_irqsave(&p->pi_lock, rf.flags); p->state = TASK_RUNNING; #ifdef CONFIG_SMP /* * Fork balancing, do it here and not earlier because: * - cpus_allowed can change in the fork path * - any previously selected cpu might disappear through hotplug * * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq, * as we're not fully set-up yet. */ __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0)); #endif rq = __task_rq_lock(p, &rf); post_init_entity_util_avg(&p->se); activate_task(rq, p, 0); p->on_rq = TASK_ON_RQ_QUEUED; trace_sched_wakeup_new(p); check_preempt_curr(rq, p, WF_FORK); #ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* * Nothing relies on rq->lock after this, so its fine to * drop it. */ lockdep_unpin_lock(&rq->lock, rf.cookie); p->sched_class->task_woken(rq, p); lockdep_repin_lock(&rq->lock, rf.cookie); } #endif task_rq_unlock(rq, p, &rf); } #ifdef CONFIG_PREEMPT_NOTIFIERS static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE; void preempt_notifier_inc(void) { static_key_slow_inc(&preempt_notifier_key); } EXPORT_SYMBOL_GPL(preempt_notifier_inc); void preempt_notifier_dec(void) { static_key_slow_dec(&preempt_notifier_key); } EXPORT_SYMBOL_GPL(preempt_notifier_dec); /** * preempt_notifier_register - tell me when current is being preempted & rescheduled * @notifier: notifier struct to register */ void preempt_notifier_register(struct preempt_notifier *notifier) { if (!static_key_false(&preempt_notifier_key)) WARN(1, "registering preempt_notifier while notifiers disabled\n"); hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); } EXPORT_SYMBOL_GPL(preempt_notifier_register); /** * preempt_notifier_unregister - no longer interested in preemption notifications * @notifier: notifier struct to unregister * * This is *not* safe to call from within a preemption notifier. */ void preempt_notifier_unregister(struct preempt_notifier *notifier) { hlist_del(¬ifier->link); } EXPORT_SYMBOL_GPL(preempt_notifier_unregister); static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) { struct preempt_notifier *notifier; hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) notifier->ops->sched_in(notifier, raw_smp_processor_id()); } static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) { if (static_key_false(&preempt_notifier_key)) __fire_sched_in_preempt_notifiers(curr); } static void __fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { struct preempt_notifier *notifier; hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) notifier->ops->sched_out(notifier, next); } static __always_inline void fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { if (static_key_false(&preempt_notifier_key)) __fire_sched_out_preempt_notifiers(curr, next); } #else /* !CONFIG_PREEMPT_NOTIFIERS */ static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) { } static inline void fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { } #endif /* CONFIG_PREEMPT_NOTIFIERS */ /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch * @prev: the current task that is being switched out * @next: the task we are going to switch to. * * This is called with the rq lock held and interrupts off. It must * be paired with a subsequent finish_task_switch after the context * switch. * * prepare_task_switch sets up locking and calls architecture specific * hooks. */ static inline void prepare_task_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) { sched_info_switch(rq, prev, next); perf_event_task_sched_out(prev, next); fire_sched_out_preempt_notifiers(prev, next); prepare_lock_switch(rq, next); prepare_arch_switch(next); } /** * finish_task_switch - clean up after a task-switch * @prev: the thread we just switched away from. * * finish_task_switch must be called after the context switch, paired * with a prepare_task_switch call before the context switch. * finish_task_switch will reconcile locking set up by prepare_task_switch, * and do any other architecture-specific cleanup actions. * * Note that we may have delayed dropping an mm in context_switch(). If * so, we finish that here outside of the runqueue lock. (Doing it * with the lock held can cause deadlocks; see schedule() for * details.) * * The context switch have flipped the stack from under us and restored the * local variables which were saved when this task called schedule() in the * past. prev == current is still correct but we need to recalculate this_rq * because prev may have moved to another CPU. */ static struct rq *finish_task_switch(struct task_struct *prev) __releases(rq->lock) { struct rq *rq = this_rq(); struct mm_struct *mm = rq->prev_mm; long prev_state; /* * The previous task will have left us with a preempt_count of 2 * because it left us after: * * schedule() * preempt_disable(); // 1 * __schedule() * raw_spin_lock_irq(&rq->lock) // 2 * * Also, see FORK_PREEMPT_COUNT. */ if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, "corrupted preempt_count: %s/%d/0x%x\n", current->comm, current->pid, preempt_count())) preempt_count_set(FORK_PREEMPT_COUNT); rq->prev_mm = NULL; /* * A task struct has one reference for the use as "current". * If a task dies, then it sets TASK_DEAD in tsk->state and calls * schedule one last time. The schedule call will never return, and * the scheduled task must drop that reference. * * We must observe prev->state before clearing prev->on_cpu (in * finish_lock_switch), otherwise a concurrent wakeup can get prev * running on another CPU and we could rave with its RUNNING -> DEAD * transition, resulting in a double drop. */ prev_state = prev->state; vtime_task_switch(prev); perf_event_task_sched_in(prev, current); finish_lock_switch(rq, prev); finish_arch_post_lock_switch(); fire_sched_in_preempt_notifiers(current); if (mm) mmdrop(mm); if (unlikely(prev_state == TASK_DEAD)) { if (prev->sched_class->task_dead) prev->sched_class->task_dead(prev); /* * Remove function-return probe instances associated with this * task and put them back on the free list. */ kprobe_flush_task(prev); /* Task is done with its stack. */ put_task_stack(prev); put_task_struct(prev); } tick_nohz_task_switch(); return rq; } #ifdef CONFIG_SMP /* rq->lock is NOT held, but preemption is disabled */ static void __balance_callback(struct rq *rq) { struct callback_head *head, *next; void (*func)(struct rq *rq); unsigned long flags; raw_spin_lock_irqsave(&rq->lock, flags); head = rq->balance_callback; rq->balance_callback = NULL; while (head) { func = (void (*)(struct rq *))head->func; next = head->next; head->next = NULL; head = next; func(rq); } raw_spin_unlock_irqrestore(&rq->lock, flags); } static inline void balance_callback(struct rq *rq) { if (unlikely(rq->balance_callback)) __balance_callback(rq); } #else static inline void balance_callback(struct rq *rq) { } #endif /** * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. */ asmlinkage __visible void schedule_tail(struct task_struct *prev) __releases(rq->lock) { struct rq *rq; /* * New tasks start with FORK_PREEMPT_COUNT, see there and * finish_task_switch() for details. * * finish_task_switch() will drop rq->lock() and lower preempt_count * and the preempt_enable() will end up enabling preemption (on * PREEMPT_COUNT kernels). */ rq = finish_task_switch(prev); balance_callback(rq); preempt_enable(); if (current->set_child_tid) put_user(task_pid_vnr(current), current->set_child_tid); } /* * context_switch - switch to the new MM and the new thread's register state. */ static __always_inline struct rq * context_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next, struct pin_cookie cookie) { struct mm_struct *mm, *oldmm; prepare_task_switch(rq, prev, next); mm = next->mm; oldmm = prev->active_mm; /* * For paravirt, this is coupled with an exit in switch_to to * combine the page table reload and the switch backend into * one hypercall. */ arch_start_context_switch(prev); if (!mm) { next->active_mm = oldmm; atomic_inc(&oldmm->mm_count); enter_lazy_tlb(oldmm, next); } else switch_mm_irqs_off(oldmm, mm, next); if (!prev->mm) { prev->active_mm = NULL; rq->prev_mm = oldmm; } /* * Since the runqueue lock will be released by the next * task (which is an invalid locking op but in the case * of the scheduler it's an obvious special-case), so we * do an early lockdep release here: */ lockdep_unpin_lock(&rq->lock, cookie); spin_release(&rq->lock.dep_map, 1, _THIS_IP_); /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); barrier(); return finish_task_switch(prev); } /* * nr_running and nr_context_switches: * * externally visible scheduler statistics: current number of runnable * threads, total number of context switches performed since bootup. */ unsigned long nr_running(void) { unsigned long i, sum = 0; for_each_online_cpu(i) sum += cpu_rq(i)->nr_running; return sum; } /* * Check if only the current task is running on the cpu. * * Caution: this function does not check that the caller has disabled * preemption, thus the result might have a time-of-check-to-time-of-use * race. The caller is responsible to use it correctly, for example: * * - from a non-preemptable section (of course) * * - from a thread that is bound to a single CPU * * - in a loop with very short iterations (e.g. a polling loop) */ bool single_task_running(void) { return raw_rq()->nr_running == 1; } EXPORT_SYMBOL(single_task_running); unsigned long long nr_context_switches(void) { int i; unsigned long long sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_switches; return sum; } unsigned long nr_iowait(void) { unsigned long i, sum = 0; for_each_possible_cpu(i) sum += atomic_read(&cpu_rq(i)->nr_iowait); return sum; } unsigned long nr_iowait_cpu(int cpu) { struct rq *this = cpu_rq(cpu); return atomic_read(&this->nr_iowait); } void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) { struct rq *rq = this_rq(); *nr_waiters = atomic_read(&rq->nr_iowait); *load = rq->load.weight; } #ifdef CONFIG_SMP /* * sched_exec - execve() is a valuable balancing opportunity, because at * this point the task has the smallest effective memory and cache footprint. */ void sched_exec(void) { struct task_struct *p = current; unsigned long flags; int dest_cpu; raw_spin_lock_irqsave(&p->pi_lock, flags); dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0); if (dest_cpu == smp_processor_id()) goto unlock; if (likely(cpu_active(dest_cpu))) { struct migration_arg arg = { p, dest_cpu }; raw_spin_unlock_irqrestore(&p->pi_lock, flags); stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); return; } unlock: raw_spin_unlock_irqrestore(&p->pi_lock, flags); } #endif DEFINE_PER_CPU(struct kernel_stat, kstat); DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat); EXPORT_PER_CPU_SYMBOL(kstat); EXPORT_PER_CPU_SYMBOL(kernel_cpustat); /* * The function fair_sched_class.update_curr accesses the struct curr * and its field curr->exec_start; when called from task_sched_runtime(), * we observe a high rate of cache misses in practice. * Prefetching this data results in improved performance. */ static inline void prefetch_curr_exec_start(struct task_struct *p) { #ifdef CONFIG_FAIR_GROUP_SCHED struct sched_entity *curr = (&p->se)->cfs_rq->curr; #else struct sched_entity *curr = (&task_rq(p)->cfs)->curr; #endif prefetch(curr); prefetch(&curr->exec_start); } /* * Return accounted runtime for the task. * In case the task is currently running, return the runtime plus current's * pending runtime that have not been accounted yet. */ unsigned long long task_sched_runtime(struct task_struct *p) { struct rq_flags rf; struct rq *rq; u64 ns; #if defined(CONFIG_64BIT) && defined(CONFIG_SMP) /* * 64-bit doesn't need locks to atomically read a 64bit value. * So we have a optimization chance when the task's delta_exec is 0. * Reading ->on_cpu is racy, but this is ok. * * If we race with it leaving cpu, we'll take a lock. So we're correct. * If we race with it entering cpu, unaccounted time is 0. This is * indistinguishable from the read occurring a few cycles earlier. * If we see ->on_cpu without ->on_rq, the task is leaving, and has * been accounted, so we're correct here as well. */ if (!p->on_cpu || !task_on_rq_queued(p)) return p->se.sum_exec_runtime; #endif rq = task_rq_lock(p, &rf); /* * Must be ->curr _and_ ->on_rq. If dequeued, we would * project cycles that may never be accounted to this * thread, breaking clock_gettime(). */ if (task_current(rq, p) && task_on_rq_queued(p)) { prefetch_curr_exec_start(p); update_rq_clock(rq); p->sched_class->update_curr(rq); } ns = p->se.sum_exec_runtime; task_rq_unlock(rq, p, &rf); return ns; } /* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. */ void scheduler_tick(void) { int cpu = smp_processor_id(); struct rq *rq = cpu_rq(cpu); struct task_struct *curr = rq->curr; sched_clock_tick(); raw_spin_lock(&rq->lock); update_rq_clock(rq); curr->sched_class->task_tick(rq, curr, 0); cpu_load_update_active(rq); calc_global_load_tick(rq); raw_spin_unlock(&rq->lock); perf_event_task_tick(); #ifdef CONFIG_SMP rq->idle_balance = idle_cpu(cpu); trigger_load_balance(rq); #endif rq_last_tick_reset(rq); } #ifdef CONFIG_NO_HZ_FULL /** * scheduler_tick_max_deferment * * Keep at least one tick per second when a single * active task is running because the scheduler doesn't * yet completely support full dynticks environment. * * This makes sure that uptime, CFS vruntime, load * balancing, etc... continue to move forward, even * with a very low granularity. * * Return: Maximum deferment in nanoseconds. */ u64 scheduler_tick_max_deferment(void) { struct rq *rq = this_rq(); unsigned long next, now = READ_ONCE(jiffies); next = rq->last_sched_tick + HZ; if (time_before_eq(next, now)) return 0; return jiffies_to_nsecs(next - now); } #endif #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \ defined(CONFIG_PREEMPT_TRACER)) /* * If the value passed in is equal to the current preempt count * then we just disabled preemption. Start timing the latency. */ static inline void preempt_latency_start(int val) { if (preempt_count() == val) { unsigned long ip = get_lock_parent_ip(); #ifdef CONFIG_DEBUG_PREEMPT current->preempt_disable_ip = ip; #endif trace_preempt_off(CALLER_ADDR0, ip); } } void preempt_count_add(int val) { #ifdef CONFIG_DEBUG_PREEMPT /* * Underflow? */ if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0))) return; #endif __preempt_count_add(val); #ifdef CONFIG_DEBUG_PREEMPT /* * Spinlock count overflowing soon? */ DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK - 10); #endif preempt_latency_start(val); } EXPORT_SYMBOL(preempt_count_add); NOKPROBE_SYMBOL(preempt_count_add); /* * If the value passed in equals to the current preempt count * then we just enabled preemption. Stop timing the latency. */ static inline void preempt_latency_stop(int val) { if (preempt_count() == val) trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); } void preempt_count_sub(int val) { #ifdef CONFIG_DEBUG_PREEMPT /* * Underflow? */ if (DEBUG_LOCKS_WARN_ON(val > preempt_count())) return; /* * Is the spinlock portion underflowing? */ if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK))) return; #endif preempt_latency_stop(val); __preempt_count_sub(val); } EXPORT_SYMBOL(preempt_count_sub); NOKPROBE_SYMBOL(preempt_count_sub); #else static inline void preempt_latency_start(int val) { } static inline void preempt_latency_stop(int val) { } #endif /* * Print scheduling while atomic bug: */ static noinline void __schedule_bug(struct task_struct *prev) { /* Save this before calling printk(), since that will clobber it */ unsigned long preempt_disable_ip = get_preempt_disable_ip(current); if (oops_in_progress) return; printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n", prev->comm, prev->pid, preempt_count()); debug_show_held_locks(prev); print_modules(); if (irqs_disabled()) print_irqtrace_events(prev); if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) && in_atomic_preempt_off()) { pr_err("Preemption disabled at:"); print_ip_sym(preempt_disable_ip); pr_cont("\n"); } if (panic_on_warn) panic("scheduling while atomic\n"); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } /* * Various schedule()-time debugging checks and statistics: */ static inline void schedule_debug(struct task_struct *prev) { #ifdef CONFIG_SCHED_STACK_END_CHECK if (task_stack_end_corrupted(prev)) panic("corrupted stack end detected inside scheduler\n"); #endif if (unlikely(in_atomic_preempt_off())) { __schedule_bug(prev); preempt_count_set(PREEMPT_DISABLED); } rcu_sleep_check(); profile_hit(SCHED_PROFILING, __builtin_return_address(0)); schedstat_inc(this_rq()->sched_count); } /* * Pick up the highest-prio task: */ static inline struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie) { const struct sched_class *class = &fair_sched_class; struct task_struct *p; /* * Optimization: we know that if all tasks are in * the fair class we can call that function directly: */ if (likely(prev->sched_class == class && rq->nr_running == rq->cfs.h_nr_running)) { p = fair_sched_class.pick_next_task(rq, prev, cookie); if (unlikely(p == RETRY_TASK)) goto again; /* assumes fair_sched_class->next == idle_sched_class */ if (unlikely(!p)) p = idle_sched_class.pick_next_task(rq, prev, cookie); return p; } again: for_each_class(class) { p = class->pick_next_task(rq, prev, cookie); if (p) { if (unlikely(p == RETRY_TASK)) goto again; return p; } } BUG(); /* the idle class will always have a runnable task */ } /* * __schedule() is the main scheduler function. * * The main means of driving the scheduler and thus entering this function are: * * 1. Explicit blocking: mutex, semaphore, waitqueue, etc. * * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return * paths. For example, see arch/x86/entry_64.S. * * To drive preemption between tasks, the scheduler sets the flag in timer * interrupt handler scheduler_tick(). * * 3. Wakeups don't really cause entry into schedule(). They add a * task to the run-queue and that's it. * * Now, if the new task added to the run-queue preempts the current * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets * called on the nearest possible occasion: * * - If the kernel is preemptible (CONFIG_PREEMPT=y): * * - in syscall or exception context, at the next outmost * preempt_enable(). (this might be as soon as the wake_up()'s * spin_unlock()!) * * - in IRQ context, return from interrupt-handler to * preemptible context * * - If the kernel is not preemptible (CONFIG_PREEMPT is not set) * then at the next: * * - cond_resched() call * - explicit schedule() call * - return from syscall or exception to user-space * - return from interrupt-handler to user-space * * WARNING: must be called with preemption disabled! */ static void __sched notrace __schedule(bool preempt) { struct task_struct *prev, *next; unsigned long *switch_count; struct pin_cookie cookie; struct rq *rq; int cpu; cpu = smp_processor_id(); rq = cpu_rq(cpu); prev = rq->curr; schedule_debug(prev); if (sched_feat(HRTICK)) hrtick_clear(rq); local_irq_disable(); rcu_note_context_switch(); /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) * done by the caller to avoid the race with signal_wake_up(). */ smp_mb__before_spinlock(); raw_spin_lock(&rq->lock); cookie = lockdep_pin_lock(&rq->lock); rq->clock_skip_update <<= 1; /* promote REQ to ACT */ switch_count = &prev->nivcsw; if (!preempt && prev->state) { if (unlikely(signal_pending_state(prev->state, prev))) { prev->state = TASK_RUNNING; } else { deactivate_task(rq, prev, DEQUEUE_SLEEP); prev->on_rq = 0; /* * If a worker went to sleep, notify and ask workqueue * whether it wants to wake up a task to maintain * concurrency. */ if (prev->flags & PF_WQ_WORKER) { struct task_struct *to_wakeup; to_wakeup = wq_worker_sleeping(prev); if (to_wakeup) try_to_wake_up_local(to_wakeup, cookie); } } switch_count = &prev->nvcsw; } if (task_on_rq_queued(prev)) update_rq_clock(rq); next = pick_next_task(rq, prev, cookie); clear_tsk_need_resched(prev); clear_preempt_need_resched(); rq->clock_skip_update = 0; if (likely(prev != next)) { rq->nr_switches++; rq->curr = next; ++*switch_count; trace_sched_switch(preempt, prev, next); rq = context_switch(rq, prev, next, cookie); /* unlocks the rq */ } else { lockdep_unpin_lock(&rq->lock, cookie); raw_spin_unlock_irq(&rq->lock); } balance_callback(rq); } void __noreturn do_task_dead(void) { /* * The setting of TASK_RUNNING by try_to_wake_up() may be delayed * when the following two conditions become true. * - There is race condition of mmap_sem (It is acquired by * exit_mm()), and * - SMI occurs before setting TASK_RUNINNG. * (or hypervisor of virtual machine switches to other guest) * As a result, we may become TASK_RUNNING after becoming TASK_DEAD * * To avoid it, we have to wait for releasing tsk->pi_lock which * is held by try_to_wake_up() */ smp_mb(); raw_spin_unlock_wait(¤t->pi_lock); /* causes final put_task_struct in finish_task_switch(). */ __set_current_state(TASK_DEAD); current->flags |= PF_NOFREEZE; /* tell freezer to ignore us */ __schedule(false); BUG(); /* Avoid "noreturn function does return". */ for (;;) cpu_relax(); /* For when BUG is null */ } static inline void sched_submit_work(struct task_struct *tsk) { if (!tsk->state || tsk_is_pi_blocked(tsk)) return; /* * If we are going to sleep and we have plugged IO queued, * make sure to submit it to avoid deadlocks. */ if (blk_needs_flush_plug(tsk)) blk_schedule_flush_plug(tsk); } asmlinkage __visible void __sched schedule(void) { struct task_struct *tsk = current; sched_submit_work(tsk); do { preempt_disable(); __schedule(false); sched_preempt_enable_no_resched(); } while (need_resched()); } EXPORT_SYMBOL(schedule); #ifdef CONFIG_CONTEXT_TRACKING asmlinkage __visible void __sched schedule_user(void) { /* * If we come here after a random call to set_need_resched(), * or we have been woken up remotely but the IPI has not yet arrived, * we haven't yet exited the RCU idle mode. Do it here manually until * we find a better solution. * * NB: There are buggy callers of this function. Ideally we * should warn if prev_state != CONTEXT_USER, but that will trigger * too frequently to make sense yet. */ enum ctx_state prev_state = exception_enter(); schedule(); exception_exit(prev_state); } #endif /** * schedule_preempt_disabled - called with preemption disabled * * Returns with preemption disabled. Note: preempt_count must be 1 */ void __sched schedule_preempt_disabled(void) { sched_preempt_enable_no_resched(); schedule(); preempt_disable(); } static void __sched notrace preempt_schedule_common(void) { do { /* * Because the function tracer can trace preempt_count_sub() * and it also uses preempt_enable/disable_notrace(), if * NEED_RESCHED is set, the preempt_enable_notrace() called * by the function tracer will call this function again and * cause infinite recursion. * * Preemption must be disabled here before the function * tracer can trace. Break up preempt_disable() into two * calls. One to disable preemption without fear of being * traced. The other to still record the preemption latency, * which can also be traced by the function tracer. */ preempt_disable_notrace(); preempt_latency_start(1); __schedule(true); preempt_latency_stop(1); preempt_enable_no_resched_notrace(); /* * Check again in case we missed a preemption opportunity * between schedule and now. */ } while (need_resched()); } #ifdef CONFIG_PREEMPT /* * this is the entry point to schedule() from in-kernel preemption * off of preempt_enable. Kernel preemptions off return from interrupt * occur there and call schedule directly. */ asmlinkage __visible void __sched notrace preempt_schedule(void) { /* * If there is a non-zero preempt_count or interrupts are disabled, * we do not want to preempt the current task. Just return.. */ if (likely(!preemptible())) return; preempt_schedule_common(); } NOKPROBE_SYMBOL(preempt_schedule); EXPORT_SYMBOL(preempt_schedule); /** * preempt_schedule_notrace - preempt_schedule called by tracing * * The tracing infrastructure uses preempt_enable_notrace to prevent * recursion and tracing preempt enabling caused by the tracing * infrastructure itself. But as tracing can happen in areas coming * from userspace or just about to enter userspace, a preempt enable * can occur before user_exit() is called. This will cause the scheduler * to be called when the system is still in usermode. * * To prevent this, the preempt_enable_notrace will use this function * instead of preempt_schedule() to exit user context if needed before * calling the scheduler. */ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) { enum ctx_state prev_ctx; if (likely(!preemptible())) return; do { /* * Because the function tracer can trace preempt_count_sub() * and it also uses preempt_enable/disable_notrace(), if * NEED_RESCHED is set, the preempt_enable_notrace() called * by the function tracer will call this function again and * cause infinite recursion. * * Preemption must be disabled here before the function * tracer can trace. Break up preempt_disable() into two * calls. One to disable preemption without fear of being * traced. The other to still record the preemption latency, * which can also be traced by the function tracer. */ preempt_disable_notrace(); preempt_latency_start(1); /* * Needs preempt disabled in case user_exit() is traced * and the tracer calls preempt_enable_notrace() causing * an infinite recursion. */ prev_ctx = exception_enter(); __schedule(true); exception_exit(prev_ctx); preempt_latency_stop(1); preempt_enable_no_resched_notrace(); } while (need_resched()); } EXPORT_SYMBOL_GPL(preempt_schedule_notrace); #endif /* CONFIG_PREEMPT */ /* * this is the entry point to schedule() from kernel preemption * off of irq context. * Note, that this is called and return with irqs disabled. This will * protect us against recursive calling from irq. */ asmlinkage __visible void __sched preempt_schedule_irq(void) { enum ctx_state prev_state; /* Catch callers which need to be fixed */ BUG_ON(preempt_count() || !irqs_disabled()); prev_state = exception_enter(); do { preempt_disable(); local_irq_enable(); __schedule(true); local_irq_disable(); sched_preempt_enable_no_resched(); } while (need_resched()); exception_exit(prev_state); } int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags, void *key) { return try_to_wake_up(curr->private, mode, wake_flags); } EXPORT_SYMBOL(default_wake_function); #ifdef CONFIG_RT_MUTEXES /* * rt_mutex_setprio - set the current priority of a task * @p: task * @prio: prio value (kernel-internal form) * * This function changes the 'effective' priority of a task. It does * not touch ->normal_prio like __setscheduler(). * * Used by the rt_mutex code to implement priority inheritance * logic. Call site only calls if the priority of the task changed. */ void rt_mutex_setprio(struct task_struct *p, int prio) { int oldprio, queued, running, queue_flag = DEQUEUE_SAVE | DEQUEUE_MOVE; const struct sched_class *prev_class; struct rq_flags rf; struct rq *rq; BUG_ON(prio > MAX_PRIO); rq = __task_rq_lock(p, &rf); /* * Idle task boosting is a nono in general. There is one * exception, when PREEMPT_RT and NOHZ is active: * * The idle task calls get_next_timer_interrupt() and holds * the timer wheel base->lock on the CPU and another CPU wants * to access the timer (probably to cancel it). We can safely * ignore the boosting request, as the idle CPU runs this code * with interrupts disabled and will complete the lock * protected section without being interrupted. So there is no * real need to boost. */ if (unlikely(p == rq->idle)) { WARN_ON(p != rq->curr); WARN_ON(p->pi_blocked_on); goto out_unlock; } trace_sched_pi_setprio(p, prio); oldprio = p->prio; if (oldprio == prio) queue_flag &= ~DEQUEUE_MOVE; prev_class = p->sched_class; queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, queue_flag); if (running) put_prev_task(rq, p); /* * Boosting condition are: * 1. -rt task is running and holds mutex A * --> -dl task blocks on mutex A * * 2. -dl task is running and holds mutex A * --> -dl task blocks on mutex A and could preempt the * running task */ if (dl_prio(prio)) { struct task_struct *pi_task = rt_mutex_get_top_task(p); if (!dl_prio(p->normal_prio) || (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) { p->dl.dl_boosted = 1; queue_flag |= ENQUEUE_REPLENISH; } else p->dl.dl_boosted = 0; p->sched_class = &dl_sched_class; } else if (rt_prio(prio)) { if (dl_prio(oldprio)) p->dl.dl_boosted = 0; if (oldprio < prio) queue_flag |= ENQUEUE_HEAD; p->sched_class = &rt_sched_class; } else { if (dl_prio(oldprio)) p->dl.dl_boosted = 0; if (rt_prio(oldprio)) p->rt.timeout = 0; p->sched_class = &fair_sched_class; } p->prio = prio; if (queued) enqueue_task(rq, p, queue_flag); if (running) set_curr_task(rq, p); check_class_changed(rq, p, prev_class, oldprio); out_unlock: preempt_disable(); /* avoid rq from going away on us */ __task_rq_unlock(rq, &rf); balance_callback(rq); preempt_enable(); } #endif void set_user_nice(struct task_struct *p, long nice) { bool queued, running; int old_prio, delta; struct rq_flags rf; struct rq *rq; if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) return; /* * We have to be careful, if called from sys_setpriority(), * the task might be in the middle of scheduling on another CPU. */ rq = task_rq_lock(p, &rf); /* * The RT priorities are set via sched_setscheduler(), but we still * allow the 'normal' nice value to be set - but as expected * it wont have any effect on scheduling until the task is * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR: */ if (task_has_dl_policy(p) || task_has_rt_policy(p)) { p->static_prio = NICE_TO_PRIO(nice); goto out_unlock; } queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, DEQUEUE_SAVE); if (running) put_prev_task(rq, p); p->static_prio = NICE_TO_PRIO(nice); set_load_weight(p); old_prio = p->prio; p->prio = effective_prio(p); delta = p->prio - old_prio; if (queued) { enqueue_task(rq, p, ENQUEUE_RESTORE); /* * If the task increased its priority or is running and * lowered its priority, then reschedule its CPU: */ if (delta < 0 || (delta > 0 && task_running(rq, p))) resched_curr(rq); } if (running) set_curr_task(rq, p); out_unlock: task_rq_unlock(rq, p, &rf); } EXPORT_SYMBOL(set_user_nice); /* * can_nice - check if a task can reduce its nice value * @p: task * @nice: nice value */ int can_nice(const struct task_struct *p, const int nice) { /* convert nice value [19,-20] to rlimit style value [1,40] */ int nice_rlim = nice_to_rlimit(nice); return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) || capable(CAP_SYS_NICE)); } #ifdef __ARCH_WANT_SYS_NICE /* * sys_nice - change the priority of the current process. * @increment: priority increment * * sys_setpriority is a more generic, but much slower function that * does similar things. */ SYSCALL_DEFINE1(nice, int, increment) { long nice, retval; /* * Setpriority might change our priority at the same moment. * We don't have to worry. Conceptually one call occurs first * and we have a single winner. */ increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH); nice = task_nice(current) + increment; nice = clamp_val(nice, MIN_NICE, MAX_NICE); if (increment < 0 && !can_nice(current, nice)) return -EPERM; retval = security_task_setnice(current, nice); if (retval) return retval; set_user_nice(current, nice); return 0; } #endif /** * task_prio - return the priority value of a given task. * @p: the task in question. * * Return: The priority value as seen by users in /proc. * RT tasks are offset by -200. Normal tasks are centered * around 0, value goes from -16 to +15. */ int task_prio(const struct task_struct *p) { return p->prio - MAX_RT_PRIO; } /** * idle_cpu - is a given cpu idle currently? * @cpu: the processor in question. * * Return: 1 if the CPU is currently idle. 0 otherwise. */ int idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); if (rq->curr != rq->idle) return 0; if (rq->nr_running) return 0; #ifdef CONFIG_SMP if (!llist_empty(&rq->wake_list)) return 0; #endif return 1; } /** * idle_task - return the idle task for a given cpu. * @cpu: the processor in question. * * Return: The idle task for the cpu @cpu. */ struct task_struct *idle_task(int cpu) { return cpu_rq(cpu)->idle; } /** * find_process_by_pid - find a process with a matching PID value. * @pid: the pid in question. * * The task of @pid, if found. %NULL otherwise. */ static struct task_struct *find_process_by_pid(pid_t pid) { return pid ? find_task_by_vpid(pid) : current; } /* * This function initializes the sched_dl_entity of a newly becoming * SCHED_DEADLINE task. * * Only the static values are considered here, the actual runtime and the * absolute deadline will be properly calculated when the task is enqueued * for the first time with its new policy. */ static void __setparam_dl(struct task_struct *p, const struct sched_attr *attr) { struct sched_dl_entity *dl_se = &p->dl; dl_se->dl_runtime = attr->sched_runtime; dl_se->dl_deadline = attr->sched_deadline; dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline; dl_se->flags = attr->sched_flags; dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime); /* * Changing the parameters of a task is 'tricky' and we're not doing * the correct thing -- also see task_dead_dl() and switched_from_dl(). * * What we SHOULD do is delay the bandwidth release until the 0-lag * point. This would include retaining the task_struct until that time * and change dl_overflow() to not immediately decrement the current * amount. * * Instead we retain the current runtime/deadline and let the new * parameters take effect after the current reservation period lapses. * This is safe (albeit pessimistic) because the 0-lag point is always * before the current scheduling deadline. * * We can still have temporary overloads because we do not delay the * change in bandwidth until that time; so admission control is * not on the safe side. It does however guarantee tasks will never * consume more than promised. */ } /* * sched_setparam() passes in -1 for its policy, to let the functions * it calls know not to change it. */ #define SETPARAM_POLICY -1 static void __setscheduler_params(struct task_struct *p, const struct sched_attr *attr) { int policy = attr->sched_policy; if (policy == SETPARAM_POLICY) policy = p->policy; p->policy = policy; if (dl_policy(policy)) __setparam_dl(p, attr); else if (fair_policy(policy)) p->static_prio = NICE_TO_PRIO(attr->sched_nice); /* * __sched_setscheduler() ensures attr->sched_priority == 0 when * !rt_policy. Always setting this ensures that things like * getparam()/getattr() don't report silly values for !rt tasks. */ p->rt_priority = attr->sched_priority; p->normal_prio = normal_prio(p); set_load_weight(p); } /* Actually do priority change: must hold pi & rq lock. */ static void __setscheduler(struct rq *rq, struct task_struct *p, const struct sched_attr *attr, bool keep_boost) { __setscheduler_params(p, attr); /* * Keep a potential priority boosting if called from * sched_setscheduler(). */ if (keep_boost) p->prio = rt_mutex_get_effective_prio(p, normal_prio(p)); else p->prio = normal_prio(p); if (dl_prio(p->prio)) p->sched_class = &dl_sched_class; else if (rt_prio(p->prio)) p->sched_class = &rt_sched_class; else p->sched_class = &fair_sched_class; } static void __getparam_dl(struct task_struct *p, struct sched_attr *attr) { struct sched_dl_entity *dl_se = &p->dl; attr->sched_priority = p->rt_priority; attr->sched_runtime = dl_se->dl_runtime; attr->sched_deadline = dl_se->dl_deadline; attr->sched_period = dl_se->dl_period; attr->sched_flags = dl_se->flags; } /* * This function validates the new parameters of a -deadline task. * We ask for the deadline not being zero, and greater or equal * than the runtime, as well as the period of being zero or * greater than deadline. Furthermore, we have to be sure that * user parameters are above the internal resolution of 1us (we * check sched_runtime only since it is always the smaller one) and * below 2^63 ns (we have to check both sched_deadline and * sched_period, as the latter can be zero). */ static bool __checkparam_dl(const struct sched_attr *attr) { /* deadline != 0 */ if (attr->sched_deadline == 0) return false; /* * Since we truncate DL_SCALE bits, make sure we're at least * that big. */ if (attr->sched_runtime < (1ULL << DL_SCALE)) return false; /* * Since we use the MSB for wrap-around and sign issues, make * sure it's not set (mind that period can be equal to zero). */ if (attr->sched_deadline & (1ULL << 63) || attr->sched_period & (1ULL << 63)) return false; /* runtime <= deadline <= period (if period != 0) */ if ((attr->sched_period != 0 && attr->sched_period < attr->sched_deadline) || attr->sched_deadline < attr->sched_runtime) return false; return true; } /* * check the target process has a UID that matches the current process's */ static bool check_same_owner(struct task_struct *p) { const struct cred *cred = current_cred(), *pcred; bool match; rcu_read_lock(); pcred = __task_cred(p); match = (uid_eq(cred->euid, pcred->euid) || uid_eq(cred->euid, pcred->uid)); rcu_read_unlock(); return match; } static bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr) { struct sched_dl_entity *dl_se = &p->dl; if (dl_se->dl_runtime != attr->sched_runtime || dl_se->dl_deadline != attr->sched_deadline || dl_se->dl_period != attr->sched_period || dl_se->flags != attr->sched_flags) return true; return false; } static int __sched_setscheduler(struct task_struct *p, const struct sched_attr *attr, bool user, bool pi) { int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 : MAX_RT_PRIO - 1 - attr->sched_priority; int retval, oldprio, oldpolicy = -1, queued, running; int new_effective_prio, policy = attr->sched_policy; const struct sched_class *prev_class; struct rq_flags rf; int reset_on_fork; int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE; struct rq *rq; /* may grab non-irq protected spin_locks */ BUG_ON(in_interrupt()); recheck: /* double check policy once rq lock held */ if (policy < 0) { reset_on_fork = p->sched_reset_on_fork; policy = oldpolicy = p->policy; } else { reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK); if (!valid_policy(policy)) return -EINVAL; } if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK)) return -EINVAL; /* * Valid priorities for SCHED_FIFO and SCHED_RR are * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL, * SCHED_BATCH and SCHED_IDLE is 0. */ if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) || (!p->mm && attr->sched_priority > MAX_RT_PRIO-1)) return -EINVAL; if ((dl_policy(policy) && !__checkparam_dl(attr)) || (rt_policy(policy) != (attr->sched_priority != 0))) return -EINVAL; /* * Allow unprivileged RT tasks to decrease priority: */ if (user && !capable(CAP_SYS_NICE)) { if (fair_policy(policy)) { if (attr->sched_nice < task_nice(p) && !can_nice(p, attr->sched_nice)) return -EPERM; } if (rt_policy(policy)) { unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO); /* can't set/change the rt policy */ if (policy != p->policy && !rlim_rtprio) return -EPERM; /* can't increase priority */ if (attr->sched_priority > p->rt_priority && attr->sched_priority > rlim_rtprio) return -EPERM; } /* * Can't set/change SCHED_DEADLINE policy at all for now * (safest behavior); in the future we would like to allow * unprivileged DL tasks to increase their relative deadline * or reduce their runtime (both ways reducing utilization) */ if (dl_policy(policy)) return -EPERM; /* * Treat SCHED_IDLE as nice 20. Only allow a switch to * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. */ if (idle_policy(p->policy) && !idle_policy(policy)) { if (!can_nice(p, task_nice(p))) return -EPERM; } /* can't change other user's priorities */ if (!check_same_owner(p)) return -EPERM; /* Normal users shall not reset the sched_reset_on_fork flag */ if (p->sched_reset_on_fork && !reset_on_fork) return -EPERM; } if (user) { retval = security_task_setscheduler(p); if (retval) return retval; } /* * make sure no PI-waiters arrive (or leave) while we are * changing the priority of the task: * * To be able to change p->policy safely, the appropriate * runqueue lock must be held. */ rq = task_rq_lock(p, &rf); /* * Changing the policy of the stop threads its a very bad idea */ if (p == rq->stop) { task_rq_unlock(rq, p, &rf); return -EINVAL; } /* * If not changing anything there's no need to proceed further, * but store a possible modification of reset_on_fork. */ if (unlikely(policy == p->policy)) { if (fair_policy(policy) && attr->sched_nice != task_nice(p)) goto change; if (rt_policy(policy) && attr->sched_priority != p->rt_priority) goto change; if (dl_policy(policy) && dl_param_changed(p, attr)) goto change; p->sched_reset_on_fork = reset_on_fork; task_rq_unlock(rq, p, &rf); return 0; } change: if (user) { #ifdef CONFIG_RT_GROUP_SCHED /* * Do not allow realtime tasks into groups that have no runtime * assigned. */ if (rt_bandwidth_enabled() && rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0 && !task_group_is_autogroup(task_group(p))) { task_rq_unlock(rq, p, &rf); return -EPERM; } #endif #ifdef CONFIG_SMP if (dl_bandwidth_enabled() && dl_policy(policy)) { cpumask_t *span = rq->rd->span; /* * Don't allow tasks with an affinity mask smaller than * the entire root_domain to become SCHED_DEADLINE. We * will also fail if there's no bandwidth available. */ if (!cpumask_subset(span, &p->cpus_allowed) || rq->rd->dl_bw.bw == 0) { task_rq_unlock(rq, p, &rf); return -EPERM; } } #endif } /* recheck policy now with rq lock held */ if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { policy = oldpolicy = -1; task_rq_unlock(rq, p, &rf); goto recheck; } /* * If setscheduling to SCHED_DEADLINE (or changing the parameters * of a SCHED_DEADLINE task) we need to check if enough bandwidth * is available. */ if ((dl_policy(policy) || dl_task(p)) && dl_overflow(p, policy, attr)) { task_rq_unlock(rq, p, &rf); return -EBUSY; } p->sched_reset_on_fork = reset_on_fork; oldprio = p->prio; if (pi) { /* * Take priority boosted tasks into account. If the new * effective priority is unchanged, we just store the new * normal parameters and do not touch the scheduler class and * the runqueue. This will be done when the task deboost * itself. */ new_effective_prio = rt_mutex_get_effective_prio(p, newprio); if (new_effective_prio == oldprio) queue_flags &= ~DEQUEUE_MOVE; } queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, queue_flags); if (running) put_prev_task(rq, p); prev_class = p->sched_class; __setscheduler(rq, p, attr, pi); if (queued) { /* * We enqueue to tail when the priority of a task is * increased (user space view). */ if (oldprio < p->prio) queue_flags |= ENQUEUE_HEAD; enqueue_task(rq, p, queue_flags); } if (running) set_curr_task(rq, p); check_class_changed(rq, p, prev_class, oldprio); preempt_disable(); /* avoid rq from going away on us */ task_rq_unlock(rq, p, &rf); if (pi) rt_mutex_adjust_pi(p); /* * Run balance callbacks after we've adjusted the PI chain. */ balance_callback(rq); preempt_enable(); return 0; } static int _sched_setscheduler(struct task_struct *p, int policy, const struct sched_param *param, bool check) { struct sched_attr attr = { .sched_policy = policy, .sched_priority = param->sched_priority, .sched_nice = PRIO_TO_NICE(p->static_prio), }; /* Fixup the legacy SCHED_RESET_ON_FORK hack. */ if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) { attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; policy &= ~SCHED_RESET_ON_FORK; attr.sched_policy = policy; } return __sched_setscheduler(p, &attr, check, true); } /** * sched_setscheduler - change the scheduling policy and/or RT priority of a thread. * @p: the task in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Return: 0 on success. An error code otherwise. * * NOTE that the task may be already dead. */ int sched_setscheduler(struct task_struct *p, int policy, const struct sched_param *param) { return _sched_setscheduler(p, policy, param, true); } EXPORT_SYMBOL_GPL(sched_setscheduler); int sched_setattr(struct task_struct *p, const struct sched_attr *attr) { return __sched_setscheduler(p, attr, true, true); } EXPORT_SYMBOL_GPL(sched_setattr); /** * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace. * @p: the task in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Just like sched_setscheduler, only don't bother checking if the * current context has permission. For example, this is needed in * stop_machine(): we create temporary high priority worker threads, * but our caller might not have that capability. * * Return: 0 on success. An error code otherwise. */ int sched_setscheduler_nocheck(struct task_struct *p, int policy, const struct sched_param *param) { return _sched_setscheduler(p, policy, param, false); } EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck); static int do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) { struct sched_param lparam; struct task_struct *p; int retval; if (!param || pid < 0) return -EINVAL; if (copy_from_user(&lparam, param, sizeof(struct sched_param))) return -EFAULT; rcu_read_lock(); retval = -ESRCH; p = find_process_by_pid(pid); if (p != NULL) retval = sched_setscheduler(p, policy, &lparam); rcu_read_unlock(); return retval; } /* * Mimics kernel/events/core.c perf_copy_attr(). */ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr) { u32 size; int ret; if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0)) return -EFAULT; /* * zero the full structure, so that a short copy will be nice. */ memset(attr, 0, sizeof(*attr)); ret = get_user(size, &uattr->size); if (ret) return ret; if (size > PAGE_SIZE) /* silly large */ goto err_size; if (!size) /* abi compat */ size = SCHED_ATTR_SIZE_VER0; if (size < SCHED_ATTR_SIZE_VER0) goto err_size; /* * If we're handed a bigger struct than we know of, * ensure all the unknown bits are 0 - i.e. new * user-space does not rely on any kernel feature * extensions we dont know about yet. */ if (size > sizeof(*attr)) { unsigned char __user *addr; unsigned char __user *end; unsigned char val; addr = (void __user *)uattr + sizeof(*attr); end = (void __user *)uattr + size; for (; addr < end; addr++) { ret = get_user(val, addr); if (ret) return ret; if (val) goto err_size; } size = sizeof(*attr); } ret = copy_from_user(attr, uattr, size); if (ret) return -EFAULT; /* * XXX: do we want to be lenient like existing syscalls; or do we want * to be strict and return an error on out-of-bounds values? */ attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE); return 0; err_size: put_user(sizeof(*attr), &uattr->size); return -E2BIG; } /** * sys_sched_setscheduler - set/change the scheduler policy and RT priority * @pid: the pid in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param) { /* negative values for policy are not valid */ if (policy < 0) return -EINVAL; return do_sched_setscheduler(pid, policy, param); } /** * sys_sched_setparam - set/change the RT priority of a thread * @pid: the pid in question. * @param: structure containing the new RT priority. * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param) { return do_sched_setscheduler(pid, SETPARAM_POLICY, param); } /** * sys_sched_setattr - same as above, but with extended sched_attr * @pid: the pid in question. * @uattr: structure containing the extended parameters. * @flags: for future extension. */ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr, unsigned int, flags) { struct sched_attr attr; struct task_struct *p; int retval; if (!uattr || pid < 0 || flags) return -EINVAL; retval = sched_copy_attr(uattr, &attr); if (retval) return retval; if ((int)attr.sched_policy < 0) return -EINVAL; rcu_read_lock(); retval = -ESRCH; p = find_process_by_pid(pid); if (p != NULL) retval = sched_setattr(p, &attr); rcu_read_unlock(); return retval; } /** * sys_sched_getscheduler - get the policy (scheduling class) of a thread * @pid: the pid in question. * * Return: On success, the policy of the thread. Otherwise, a negative error * code. */ SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid) { struct task_struct *p; int retval; if (pid < 0) return -EINVAL; retval = -ESRCH; rcu_read_lock(); p = find_process_by_pid(pid); if (p) { retval = security_task_getscheduler(p); if (!retval) retval = p->policy | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0); } rcu_read_unlock(); return retval; } /** * sys_sched_getparam - get the RT priority of a thread * @pid: the pid in question. * @param: structure containing the RT priority. * * Return: On success, 0 and the RT priority is in @param. Otherwise, an error * code. */ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param) { struct sched_param lp = { .sched_priority = 0 }; struct task_struct *p; int retval; if (!param || pid < 0) return -EINVAL; rcu_read_lock(); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) goto out_unlock; retval = security_task_getscheduler(p); if (retval) goto out_unlock; if (task_has_rt_policy(p)) lp.sched_priority = p->rt_priority; rcu_read_unlock(); /* * This one might sleep, we cannot do it with a spinlock held ... */ retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0; return retval; out_unlock: rcu_read_unlock(); return retval; } static int sched_read_attr(struct sched_attr __user *uattr, struct sched_attr *attr, unsigned int usize) { int ret; if (!access_ok(VERIFY_WRITE, uattr, usize)) return -EFAULT; /* * If we're handed a smaller struct than we know of, * ensure all the unknown bits are 0 - i.e. old * user-space does not get uncomplete information. */ if (usize < sizeof(*attr)) { unsigned char *addr; unsigned char *end; addr = (void *)attr + usize; end = (void *)attr + sizeof(*attr); for (; addr < end; addr++) { if (*addr) return -EFBIG; } attr->size = usize; } ret = copy_to_user(uattr, attr, attr->size); if (ret) return -EFAULT; return 0; } /** * sys_sched_getattr - similar to sched_getparam, but with sched_attr * @pid: the pid in question. * @uattr: structure containing the extended parameters. * @size: sizeof(attr) for fwd/bwd comp. * @flags: for future extension. */ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, unsigned int, size, unsigned int, flags) { struct sched_attr attr = { .size = sizeof(struct sched_attr), }; struct task_struct *p; int retval; if (!uattr || pid < 0 || size > PAGE_SIZE || size < SCHED_ATTR_SIZE_VER0 || flags) return -EINVAL; rcu_read_lock(); p = find_process_by_pid(pid); retval = -ESRCH; if (!p) goto out_unlock; retval = security_task_getscheduler(p); if (retval) goto out_unlock; attr.sched_policy = p->policy; if (p->sched_reset_on_fork) attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; if (task_has_dl_policy(p)) __getparam_dl(p, &attr); else if (task_has_rt_policy(p)) attr.sched_priority = p->rt_priority; else attr.sched_nice = task_nice(p); rcu_read_unlock(); retval = sched_read_attr(uattr, &attr, size); return retval; out_unlock: rcu_read_unlock(); return retval; } long sched_setaffinity(pid_t pid, const struct cpumask *in_mask) { cpumask_var_t cpus_allowed, new_mask; struct task_struct *p; int retval; rcu_read_lock(); p = find_process_by_pid(pid); if (!p) { rcu_read_unlock(); return -ESRCH; } /* Prevent p going away */ get_task_struct(p); rcu_read_unlock(); if (p->flags & PF_NO_SETAFFINITY) { retval = -EINVAL; goto out_put_task; } if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) { retval = -ENOMEM; goto out_put_task; } if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) { retval = -ENOMEM; goto out_free_cpus_allowed; } retval = -EPERM; if (!check_same_owner(p)) { rcu_read_lock(); if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) { rcu_read_unlock(); goto out_free_new_mask; } rcu_read_unlock(); } retval = security_task_setscheduler(p); if (retval) goto out_free_new_mask; cpuset_cpus_allowed(p, cpus_allowed); cpumask_and(new_mask, in_mask, cpus_allowed); /* * Since bandwidth control happens on root_domain basis, * if admission test is enabled, we only admit -deadline * tasks allowed to run on all the CPUs in the task's * root_domain. */ #ifdef CONFIG_SMP if (task_has_dl_policy(p) && dl_bandwidth_enabled()) { rcu_read_lock(); if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) { retval = -EBUSY; rcu_read_unlock(); goto out_free_new_mask; } rcu_read_unlock(); } #endif again: retval = __set_cpus_allowed_ptr(p, new_mask, true); if (!retval) { cpuset_cpus_allowed(p, cpus_allowed); if (!cpumask_subset(new_mask, cpus_allowed)) { /* * We must have raced with a concurrent cpuset * update. Just reset the cpus_allowed to the * cpuset's cpus_allowed */ cpumask_copy(new_mask, cpus_allowed); goto again; } } out_free_new_mask: free_cpumask_var(new_mask); out_free_cpus_allowed: free_cpumask_var(cpus_allowed); out_put_task: put_task_struct(p); return retval; } static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len, struct cpumask *new_mask) { if (len < cpumask_size()) cpumask_clear(new_mask); else if (len > cpumask_size()) len = cpumask_size(); return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0; } /** * sys_sched_setaffinity - set the cpu affinity of a process * @pid: pid of the process * @len: length in bytes of the bitmask pointed to by user_mask_ptr * @user_mask_ptr: user-space pointer to the new cpu mask * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len, unsigned long __user *, user_mask_ptr) { cpumask_var_t new_mask; int retval; if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) return -ENOMEM; retval = get_user_cpu_mask(user_mask_ptr, len, new_mask); if (retval == 0) retval = sched_setaffinity(pid, new_mask); free_cpumask_var(new_mask); return retval; } long sched_getaffinity(pid_t pid, struct cpumask *mask) { struct task_struct *p; unsigned long flags; int retval; rcu_read_lock(); retval = -ESRCH; p = find_process_by_pid(pid); if (!p) goto out_unlock; retval = security_task_getscheduler(p); if (retval) goto out_unlock; raw_spin_lock_irqsave(&p->pi_lock, flags); cpumask_and(mask, &p->cpus_allowed, cpu_active_mask); raw_spin_unlock_irqrestore(&p->pi_lock, flags); out_unlock: rcu_read_unlock(); return retval; } /** * sys_sched_getaffinity - get the cpu affinity of a process * @pid: pid of the process * @len: length in bytes of the bitmask pointed to by user_mask_ptr * @user_mask_ptr: user-space pointer to hold the current cpu mask * * Return: size of CPU mask copied to user_mask_ptr on success. An * error code otherwise. */ SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len, unsigned long __user *, user_mask_ptr) { int ret; cpumask_var_t mask; if ((len * BITS_PER_BYTE) < nr_cpu_ids) return -EINVAL; if (len & (sizeof(unsigned long)-1)) return -EINVAL; if (!alloc_cpumask_var(&mask, GFP_KERNEL)) return -ENOMEM; ret = sched_getaffinity(pid, mask); if (ret == 0) { size_t retlen = min_t(size_t, len, cpumask_size()); if (copy_to_user(user_mask_ptr, mask, retlen)) ret = -EFAULT; else ret = retlen; } free_cpumask_var(mask); return ret; } /** * sys_sched_yield - yield the current processor to other threads. * * This function yields the current CPU to other tasks. If there are no * other threads running on this CPU then this function will return. * * Return: 0. */ SYSCALL_DEFINE0(sched_yield) { struct rq *rq = this_rq_lock(); schedstat_inc(rq->yld_count); current->sched_class->yield_task(rq); /* * Since we are going to call schedule() anyway, there's * no need to preempt or enable interrupts: */ __release(rq->lock); spin_release(&rq->lock.dep_map, 1, _THIS_IP_); do_raw_spin_unlock(&rq->lock); sched_preempt_enable_no_resched(); schedule(); return 0; } #ifndef CONFIG_PREEMPT int __sched _cond_resched(void) { if (should_resched(0)) { preempt_schedule_common(); return 1; } return 0; } EXPORT_SYMBOL(_cond_resched); #endif /* * __cond_resched_lock() - if a reschedule is pending, drop the given lock, * call schedule, and on return reacquire the lock. * * This works OK both with and without CONFIG_PREEMPT. We do strange low-level * operations here to prevent schedule() from being called twice (once via * spin_unlock(), once by hand). */ int __cond_resched_lock(spinlock_t *lock) { int resched = should_resched(PREEMPT_LOCK_OFFSET); int ret = 0; lockdep_assert_held(lock); if (spin_needbreak(lock) || resched) { spin_unlock(lock); if (resched) preempt_schedule_common(); else cpu_relax(); ret = 1; spin_lock(lock); } return ret; } EXPORT_SYMBOL(__cond_resched_lock); int __sched __cond_resched_softirq(void) { BUG_ON(!in_softirq()); if (should_resched(SOFTIRQ_DISABLE_OFFSET)) { local_bh_enable(); preempt_schedule_common(); local_bh_disable(); return 1; } return 0; } EXPORT_SYMBOL(__cond_resched_softirq); /** * yield - yield the current processor to other threads. * * Do not ever use this function, there's a 99% chance you're doing it wrong. * * The scheduler is at all times free to pick the calling task as the most * eligible task to run, if removing the yield() call from your code breaks * it, its already broken. * * Typical broken usage is: * * while (!event) * yield(); * * where one assumes that yield() will let 'the other' process run that will * make event true. If the current task is a SCHED_FIFO task that will never * happen. Never use yield() as a progress guarantee!! * * If you want to use yield() to wait for something, use wait_event(). * If you want to use yield() to be 'nice' for others, use cond_resched(). * If you still want to use yield(), do not! */ void __sched yield(void) { set_current_state(TASK_RUNNING); sys_sched_yield(); } EXPORT_SYMBOL(yield); /** * yield_to - yield the current processor to another thread in * your thread group, or accelerate that thread toward the * processor it's on. * @p: target task * @preempt: whether task preemption is allowed or not * * It's the caller's job to ensure that the target task struct * can't go away on us before we can do any checks. * * Return: * true (>0) if we indeed boosted the target task. * false (0) if we failed to boost the target. * -ESRCH if there's no task to yield to. */ int __sched yield_to(struct task_struct *p, bool preempt) { struct task_struct *curr = current; struct rq *rq, *p_rq; unsigned long flags; int yielded = 0; local_irq_save(flags); rq = this_rq(); again: p_rq = task_rq(p); /* * If we're the only runnable task on the rq and target rq also * has only one task, there's absolutely no point in yielding. */ if (rq->nr_running == 1 && p_rq->nr_running == 1) { yielded = -ESRCH; goto out_irq; } double_rq_lock(rq, p_rq); if (task_rq(p) != p_rq) { double_rq_unlock(rq, p_rq); goto again; } if (!curr->sched_class->yield_to_task) goto out_unlock; if (curr->sched_class != p->sched_class) goto out_unlock; if (task_running(p_rq, p) || p->state) goto out_unlock; yielded = curr->sched_class->yield_to_task(rq, p, preempt); if (yielded) { schedstat_inc(rq->yld_count); /* * Make p's CPU reschedule; pick_next_entity takes care of * fairness. */ if (preempt && rq != p_rq) resched_curr(p_rq); } out_unlock: double_rq_unlock(rq, p_rq); out_irq: local_irq_restore(flags); if (yielded > 0) schedule(); return yielded; } EXPORT_SYMBOL_GPL(yield_to); /* * This task is about to go to sleep on IO. Increment rq->nr_iowait so * that process accounting knows that this is a task in IO wait state. */ long __sched io_schedule_timeout(long timeout) { int old_iowait = current->in_iowait; struct rq *rq; long ret; current->in_iowait = 1; blk_schedule_flush_plug(current); delayacct_blkio_start(); rq = raw_rq(); atomic_inc(&rq->nr_iowait); ret = schedule_timeout(timeout); current->in_iowait = old_iowait; atomic_dec(&rq->nr_iowait); delayacct_blkio_end(); return ret; } EXPORT_SYMBOL(io_schedule_timeout); /** * sys_sched_get_priority_max - return maximum RT priority. * @policy: scheduling class. * * Return: On success, this syscall returns the maximum * rt_priority that can be used by a given scheduling class. * On failure, a negative error code is returned. */ SYSCALL_DEFINE1(sched_get_priority_max, int, policy) { int ret = -EINVAL; switch (policy) { case SCHED_FIFO: case SCHED_RR: ret = MAX_USER_RT_PRIO-1; break; case SCHED_DEADLINE: case SCHED_NORMAL: case SCHED_BATCH: case SCHED_IDLE: ret = 0; break; } return ret; } /** * sys_sched_get_priority_min - return minimum RT priority. * @policy: scheduling class. * * Return: On success, this syscall returns the minimum * rt_priority that can be used by a given scheduling class. * On failure, a negative error code is returned. */ SYSCALL_DEFINE1(sched_get_priority_min, int, policy) { int ret = -EINVAL; switch (policy) { case SCHED_FIFO: case SCHED_RR: ret = 1; break; case SCHED_DEADLINE: case SCHED_NORMAL: case SCHED_BATCH: case SCHED_IDLE: ret = 0; } return ret; } /** * sys_sched_rr_get_interval - return the default timeslice of a process. * @pid: pid of the process. * @interval: userspace pointer to the timeslice value. * * this syscall writes the default timeslice value of a given process * into the user-space timespec buffer. A value of '0' means infinity. * * Return: On success, 0 and the timeslice is in @interval. Otherwise, * an error code. */ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, struct timespec __user *, interval) { struct task_struct *p; unsigned int time_slice; struct rq_flags rf; struct timespec t; struct rq *rq; int retval; if (pid < 0) return -EINVAL; retval = -ESRCH; rcu_read_lock(); p = find_process_by_pid(pid); if (!p) goto out_unlock; retval = security_task_getscheduler(p); if (retval) goto out_unlock; rq = task_rq_lock(p, &rf); time_slice = 0; if (p->sched_class->get_rr_interval) time_slice = p->sched_class->get_rr_interval(rq, p); task_rq_unlock(rq, p, &rf); rcu_read_unlock(); jiffies_to_timespec(time_slice, &t); retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0; return retval; out_unlock: rcu_read_unlock(); return retval; } static const char stat_nam[] = TASK_STATE_TO_CHAR_STR; void sched_show_task(struct task_struct *p) { unsigned long free = 0; int ppid; unsigned long state = p->state; if (!try_get_task_stack(p)) return; if (state) state = __ffs(state) + 1; printk(KERN_INFO "%-15.15s %c", p->comm, state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?'); if (state == TASK_RUNNING) printk(KERN_CONT " running task "); #ifdef CONFIG_DEBUG_STACK_USAGE free = stack_not_used(p); #endif ppid = 0; rcu_read_lock(); if (pid_alive(p)) ppid = task_pid_nr(rcu_dereference(p->real_parent)); rcu_read_unlock(); printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free, task_pid_nr(p), ppid, (unsigned long)task_thread_info(p)->flags); print_worker_info(KERN_INFO, p); show_stack(p, NULL); put_task_stack(p); } void show_state_filter(unsigned long state_filter) { struct task_struct *g, *p; #if BITS_PER_LONG == 32 printk(KERN_INFO " task PC stack pid father\n"); #else printk(KERN_INFO " task PC stack pid father\n"); #endif rcu_read_lock(); for_each_process_thread(g, p) { /* * reset the NMI-timeout, listing all files on a slow * console might take a lot of time: * Also, reset softlockup watchdogs on all CPUs, because * another CPU might be blocked waiting for us to process * an IPI. */ touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); if (!state_filter || (p->state & state_filter)) sched_show_task(p); } #ifdef CONFIG_SCHED_DEBUG if (!state_filter) sysrq_sched_debug_show(); #endif rcu_read_unlock(); /* * Only show locks if all tasks are dumped: */ if (!state_filter) debug_show_all_locks(); } void init_idle_bootup_task(struct task_struct *idle) { idle->sched_class = &idle_sched_class; } /** * init_idle - set up an idle thread for a given CPU * @idle: task in question * @cpu: cpu the idle task belongs to * * NOTE: this function does not set the idle thread's NEED_RESCHED * flag, to make booting more robust. */ void init_idle(struct task_struct *idle, int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; raw_spin_lock_irqsave(&idle->pi_lock, flags); raw_spin_lock(&rq->lock); __sched_fork(0, idle); idle->state = TASK_RUNNING; idle->se.exec_start = sched_clock(); kasan_unpoison_task_stack(idle); #ifdef CONFIG_SMP /* * Its possible that init_idle() gets called multiple times on a task, * in that case do_set_cpus_allowed() will not do the right thing. * * And since this is boot we can forgo the serialization. */ set_cpus_allowed_common(idle, cpumask_of(cpu)); #endif /* * We're having a chicken and egg problem, even though we are * holding rq->lock, the cpu isn't yet set to this cpu so the * lockdep check in task_group() will fail. * * Similar case to sched_fork(). / Alternatively we could * use task_rq_lock() here and obtain the other rq->lock. * * Silence PROVE_RCU */ rcu_read_lock(); __set_task_cpu(idle, cpu); rcu_read_unlock(); rq->curr = rq->idle = idle; idle->on_rq = TASK_ON_RQ_QUEUED; #ifdef CONFIG_SMP idle->on_cpu = 1; #endif raw_spin_unlock(&rq->lock); raw_spin_unlock_irqrestore(&idle->pi_lock, flags); /* Set the preempt count _outside_ the spinlocks! */ init_idle_preempt_count(idle, cpu); /* * The idle tasks have their own, simple scheduling class: */ idle->sched_class = &idle_sched_class; ftrace_graph_init_idle_task(idle, cpu); vtime_init_idle(idle, cpu); #ifdef CONFIG_SMP sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); #endif } int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial) { int ret = 1, trial_cpus; struct dl_bw *cur_dl_b; unsigned long flags; if (!cpumask_weight(cur)) return ret; rcu_read_lock_sched(); cur_dl_b = dl_bw_of(cpumask_any(cur)); trial_cpus = cpumask_weight(trial); raw_spin_lock_irqsave(&cur_dl_b->lock, flags); if (cur_dl_b->bw != -1 && cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw) ret = 0; raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags); rcu_read_unlock_sched(); return ret; } int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed) { int ret = 0; /* * Kthreads which disallow setaffinity shouldn't be moved * to a new cpuset; we don't want to change their cpu * affinity and isolating such threads by their set of * allowed nodes is unnecessary. Thus, cpusets are not * applicable for such threads. This prevents checking for * success of set_cpus_allowed_ptr() on all attached tasks * before cpus_allowed may be changed. */ if (p->flags & PF_NO_SETAFFINITY) { ret = -EINVAL; goto out; } #ifdef CONFIG_SMP if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span, cs_cpus_allowed)) { unsigned int dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed); struct dl_bw *dl_b; bool overflow; int cpus; unsigned long flags; rcu_read_lock_sched(); dl_b = dl_bw_of(dest_cpu); raw_spin_lock_irqsave(&dl_b->lock, flags); cpus = dl_bw_cpus(dest_cpu); overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw); if (overflow) ret = -EBUSY; else { /* * We reserve space for this task in the destination * root_domain, as we can't fail after this point. * We will free resources in the source root_domain * later on (see set_cpus_allowed_dl()). */ __dl_add(dl_b, p->dl.dl_bw); } raw_spin_unlock_irqrestore(&dl_b->lock, flags); rcu_read_unlock_sched(); } #endif out: return ret; } #ifdef CONFIG_SMP static bool sched_smp_initialized __read_mostly; #ifdef CONFIG_NUMA_BALANCING /* Migrate current task p to target_cpu */ int migrate_task_to(struct task_struct *p, int target_cpu) { struct migration_arg arg = { p, target_cpu }; int curr_cpu = task_cpu(p); if (curr_cpu == target_cpu) return 0; if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p))) return -EINVAL; /* TODO: This is not properly updating schedstats */ trace_sched_move_numa(p, curr_cpu, target_cpu); return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg); } /* * Requeue a task on a given node and accurately track the number of NUMA * tasks on the runqueues */ void sched_setnuma(struct task_struct *p, int nid) { bool queued, running; struct rq_flags rf; struct rq *rq; rq = task_rq_lock(p, &rf); queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, DEQUEUE_SAVE); if (running) put_prev_task(rq, p); p->numa_preferred_nid = nid; if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE); if (running) set_curr_task(rq, p); task_rq_unlock(rq, p, &rf); } #endif /* CONFIG_NUMA_BALANCING */ #ifdef CONFIG_HOTPLUG_CPU /* * Ensures that the idle task is using init_mm right before its cpu goes * offline. */ void idle_task_exit(void) { struct mm_struct *mm = current->active_mm; BUG_ON(cpu_online(smp_processor_id())); if (mm != &init_mm) { switch_mm_irqs_off(mm, &init_mm, current); finish_arch_post_lock_switch(); } mmdrop(mm); } /* * Since this CPU is going 'away' for a while, fold any nr_active delta * we might have. Assumes we're called after migrate_tasks() so that the * nr_active count is stable. We need to take the teardown thread which * is calling this into account, so we hand in adjust = 1 to the load * calculation. * * Also see the comment "Global load-average calculations". */ static void calc_load_migrate(struct rq *rq) { long delta = calc_load_fold_active(rq, 1); if (delta) atomic_long_add(delta, &calc_load_tasks); } static void put_prev_task_fake(struct rq *rq, struct task_struct *prev) { } static const struct sched_class fake_sched_class = { .put_prev_task = put_prev_task_fake, }; static struct task_struct fake_task = { /* * Avoid pull_{rt,dl}_task() */ .prio = MAX_PRIO + 1, .sched_class = &fake_sched_class, }; /* * Migrate all tasks from the rq, sleeping tasks will be migrated by * try_to_wake_up()->select_task_rq(). * * Called with rq->lock held even though we'er in stop_machine() and * there's no concurrency possible, we hold the required locks anyway * because of lock validation efforts. */ static void migrate_tasks(struct rq *dead_rq) { struct rq *rq = dead_rq; struct task_struct *next, *stop = rq->stop; struct pin_cookie cookie; int dest_cpu; /* * Fudge the rq selection such that the below task selection loop * doesn't get stuck on the currently eligible stop task. * * We're currently inside stop_machine() and the rq is either stuck * in the stop_machine_cpu_stop() loop, or we're executing this code, * either way we should never end up calling schedule() until we're * done here. */ rq->stop = NULL; /* * put_prev_task() and pick_next_task() sched * class method both need to have an up-to-date * value of rq->clock[_task] */ update_rq_clock(rq); for (;;) { /* * There's this thread running, bail when that's the only * remaining thread. */ if (rq->nr_running == 1) break; /* * pick_next_task assumes pinned rq->lock. */ cookie = lockdep_pin_lock(&rq->lock); next = pick_next_task(rq, &fake_task, cookie); BUG_ON(!next); next->sched_class->put_prev_task(rq, next); /* * Rules for changing task_struct::cpus_allowed are holding * both pi_lock and rq->lock, such that holding either * stabilizes the mask. * * Drop rq->lock is not quite as disastrous as it usually is * because !cpu_active at this point, which means load-balance * will not interfere. Also, stop-machine. */ lockdep_unpin_lock(&rq->lock, cookie); raw_spin_unlock(&rq->lock); raw_spin_lock(&next->pi_lock); raw_spin_lock(&rq->lock); /* * Since we're inside stop-machine, _nothing_ should have * changed the task, WARN if weird stuff happened, because in * that case the above rq->lock drop is a fail too. */ if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) { raw_spin_unlock(&next->pi_lock); continue; } /* Find suitable destination for @next, with force if needed. */ dest_cpu = select_fallback_rq(dead_rq->cpu, next); rq = __migrate_task(rq, next, dest_cpu); if (rq != dead_rq) { raw_spin_unlock(&rq->lock); rq = dead_rq; raw_spin_lock(&rq->lock); } raw_spin_unlock(&next->pi_lock); } rq->stop = stop; } #endif /* CONFIG_HOTPLUG_CPU */ static void set_rq_online(struct rq *rq) { if (!rq->online) { const struct sched_class *class; cpumask_set_cpu(rq->cpu, rq->rd->online); rq->online = 1; for_each_class(class) { if (class->rq_online) class->rq_online(rq); } } } static void set_rq_offline(struct rq *rq) { if (rq->online) { const struct sched_class *class; for_each_class(class) { if (class->rq_offline) class->rq_offline(rq); } cpumask_clear_cpu(rq->cpu, rq->rd->online); rq->online = 0; } } static void set_cpu_rq_start_time(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); rq->age_stamp = sched_clock_cpu(cpu); } static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */ #ifdef CONFIG_SCHED_DEBUG static __read_mostly int sched_debug_enabled; static int __init sched_debug_setup(char *str) { sched_debug_enabled = 1; return 0; } early_param("sched_debug", sched_debug_setup); static inline bool sched_debug(void) { return sched_debug_enabled; } static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level, struct cpumask *groupmask) { struct sched_group *group = sd->groups; cpumask_clear(groupmask); printk(KERN_DEBUG "%*s domain %d: ", level, "", level); if (!(sd->flags & SD_LOAD_BALANCE)) { printk("does not load-balance\n"); if (sd->parent) printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain" " has parent"); return -1; } printk(KERN_CONT "span %*pbl level %s\n", cpumask_pr_args(sched_domain_span(sd)), sd->name); if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) { printk(KERN_ERR "ERROR: domain->span does not contain " "CPU%d\n", cpu); } if (!cpumask_test_cpu(cpu, sched_group_cpus(group))) { printk(KERN_ERR "ERROR: domain->groups does not contain" " CPU%d\n", cpu); } printk(KERN_DEBUG "%*s groups:", level + 1, ""); do { if (!group) { printk("\n"); printk(KERN_ERR "ERROR: group is NULL\n"); break; } if (!cpumask_weight(sched_group_cpus(group))) { printk(KERN_CONT "\n"); printk(KERN_ERR "ERROR: empty group\n"); break; } if (!(sd->flags & SD_OVERLAP) && cpumask_intersects(groupmask, sched_group_cpus(group))) { printk(KERN_CONT "\n"); printk(KERN_ERR "ERROR: repeated CPUs\n"); break; } cpumask_or(groupmask, groupmask, sched_group_cpus(group)); printk(KERN_CONT " %*pbl", cpumask_pr_args(sched_group_cpus(group))); if (group->sgc->capacity != SCHED_CAPACITY_SCALE) { printk(KERN_CONT " (cpu_capacity = %lu)", group->sgc->capacity); } group = group->next; } while (group != sd->groups); printk(KERN_CONT "\n"); if (!cpumask_equal(sched_domain_span(sd), groupmask)) printk(KERN_ERR "ERROR: groups don't span domain->span\n"); if (sd->parent && !cpumask_subset(groupmask, sched_domain_span(sd->parent))) printk(KERN_ERR "ERROR: parent span is not a superset " "of domain->span\n"); return 0; } static void sched_domain_debug(struct sched_domain *sd, int cpu) { int level = 0; if (!sched_debug_enabled) return; if (!sd) { printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu); return; } printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu); for (;;) { if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask)) break; level++; sd = sd->parent; if (!sd) break; } } #else /* !CONFIG_SCHED_DEBUG */ # define sched_debug_enabled 0 # define sched_domain_debug(sd, cpu) do { } while (0) static inline bool sched_debug(void) { return false; } #endif /* CONFIG_SCHED_DEBUG */ static int sd_degenerate(struct sched_domain *sd) { if (cpumask_weight(sched_domain_span(sd)) == 1) return 1; /* Following flags need at least 2 groups */ if (sd->flags & (SD_LOAD_BALANCE | SD_BALANCE_NEWIDLE | SD_BALANCE_FORK | SD_BALANCE_EXEC | SD_SHARE_CPUCAPACITY | SD_ASYM_CPUCAPACITY | SD_SHARE_PKG_RESOURCES | SD_SHARE_POWERDOMAIN)) { if (sd->groups != sd->groups->next) return 0; } /* Following flags don't use groups */ if (sd->flags & (SD_WAKE_AFFINE)) return 0; return 1; } static int sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent) { unsigned long cflags = sd->flags, pflags = parent->flags; if (sd_degenerate(parent)) return 1; if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent))) return 0; /* Flags needing groups don't count if only 1 group in parent */ if (parent->groups == parent->groups->next) { pflags &= ~(SD_LOAD_BALANCE | SD_BALANCE_NEWIDLE | SD_BALANCE_FORK | SD_BALANCE_EXEC | SD_ASYM_CPUCAPACITY | SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES | SD_PREFER_SIBLING | SD_SHARE_POWERDOMAIN); if (nr_node_ids == 1) pflags &= ~SD_SERIALIZE; } if (~cflags & pflags) return 0; return 1; } static void free_rootdomain(struct rcu_head *rcu) { struct root_domain *rd = container_of(rcu, struct root_domain, rcu); cpupri_cleanup(&rd->cpupri); cpudl_cleanup(&rd->cpudl); free_cpumask_var(rd->dlo_mask); free_cpumask_var(rd->rto_mask); free_cpumask_var(rd->online); free_cpumask_var(rd->span); kfree(rd); } static void rq_attach_root(struct rq *rq, struct root_domain *rd) { struct root_domain *old_rd = NULL; unsigned long flags; raw_spin_lock_irqsave(&rq->lock, flags); if (rq->rd) { old_rd = rq->rd; if (cpumask_test_cpu(rq->cpu, old_rd->online)) set_rq_offline(rq); cpumask_clear_cpu(rq->cpu, old_rd->span); /* * If we dont want to free the old_rd yet then * set old_rd to NULL to skip the freeing later * in this function: */ if (!atomic_dec_and_test(&old_rd->refcount)) old_rd = NULL; } atomic_inc(&rd->refcount); rq->rd = rd; cpumask_set_cpu(rq->cpu, rd->span); if (cpumask_test_cpu(rq->cpu, cpu_active_mask)) set_rq_online(rq); raw_spin_unlock_irqrestore(&rq->lock, flags); if (old_rd) call_rcu_sched(&old_rd->rcu, free_rootdomain); } static int init_rootdomain(struct root_domain *rd) { memset(rd, 0, sizeof(*rd)); if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL)) goto out; if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL)) goto free_span; if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL)) goto free_online; if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL)) goto free_dlo_mask; init_dl_bw(&rd->dl_bw); if (cpudl_init(&rd->cpudl) != 0) goto free_dlo_mask; if (cpupri_init(&rd->cpupri) != 0) goto free_rto_mask; return 0; free_rto_mask: free_cpumask_var(rd->rto_mask); free_dlo_mask: free_cpumask_var(rd->dlo_mask); free_online: free_cpumask_var(rd->online); free_span: free_cpumask_var(rd->span); out: return -ENOMEM; } /* * By default the system creates a single root-domain with all cpus as * members (mimicking the global state we have today). */ struct root_domain def_root_domain; static void init_defrootdomain(void) { init_rootdomain(&def_root_domain); atomic_set(&def_root_domain.refcount, 1); } static struct root_domain *alloc_rootdomain(void) { struct root_domain *rd; rd = kmalloc(sizeof(*rd), GFP_KERNEL); if (!rd) return NULL; if (init_rootdomain(rd) != 0) { kfree(rd); return NULL; } return rd; } static void free_sched_groups(struct sched_group *sg, int free_sgc) { struct sched_group *tmp, *first; if (!sg) return; first = sg; do { tmp = sg->next; if (free_sgc && atomic_dec_and_test(&sg->sgc->ref)) kfree(sg->sgc); kfree(sg); sg = tmp; } while (sg != first); } static void destroy_sched_domain(struct sched_domain *sd) { /* * If its an overlapping domain it has private groups, iterate and * nuke them all. */ if (sd->flags & SD_OVERLAP) { free_sched_groups(sd->groups, 1); } else if (atomic_dec_and_test(&sd->groups->ref)) { kfree(sd->groups->sgc); kfree(sd->groups); } if (sd->shared && atomic_dec_and_test(&sd->shared->ref)) kfree(sd->shared); kfree(sd); } static void destroy_sched_domains_rcu(struct rcu_head *rcu) { struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu); while (sd) { struct sched_domain *parent = sd->parent; destroy_sched_domain(sd); sd = parent; } } static void destroy_sched_domains(struct sched_domain *sd) { if (sd) call_rcu(&sd->rcu, destroy_sched_domains_rcu); } /* * Keep a special pointer to the highest sched_domain that has * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this * allows us to avoid some pointer chasing select_idle_sibling(). * * Also keep a unique ID per domain (we use the first cpu number in * the cpumask of the domain), this allows us to quickly tell if * two cpus are in the same cache domain, see cpus_share_cache(). */ DEFINE_PER_CPU(struct sched_domain *, sd_llc); DEFINE_PER_CPU(int, sd_llc_size); DEFINE_PER_CPU(int, sd_llc_id); DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared); DEFINE_PER_CPU(struct sched_domain *, sd_numa); DEFINE_PER_CPU(struct sched_domain *, sd_asym); static void update_top_cache_domain(int cpu) { struct sched_domain_shared *sds = NULL; struct sched_domain *sd; int id = cpu; int size = 1; sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES); if (sd) { id = cpumask_first(sched_domain_span(sd)); size = cpumask_weight(sched_domain_span(sd)); sds = sd->shared; } rcu_assign_pointer(per_cpu(sd_llc, cpu), sd); per_cpu(sd_llc_size, cpu) = size; per_cpu(sd_llc_id, cpu) = id; rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds); sd = lowest_flag_domain(cpu, SD_NUMA); rcu_assign_pointer(per_cpu(sd_numa, cpu), sd); sd = highest_flag_domain(cpu, SD_ASYM_PACKING); rcu_assign_pointer(per_cpu(sd_asym, cpu), sd); } /* * Attach the domain 'sd' to 'cpu' as its base domain. Callers must * hold the hotplug lock. */ static void cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) { struct rq *rq = cpu_rq(cpu); struct sched_domain *tmp; /* Remove the sched domains which do not contribute to scheduling. */ for (tmp = sd; tmp; ) { struct sched_domain *parent = tmp->parent; if (!parent) break; if (sd_parent_degenerate(tmp, parent)) { tmp->parent = parent->parent; if (parent->parent) parent->parent->child = tmp; /* * Transfer SD_PREFER_SIBLING down in case of a * degenerate parent; the spans match for this * so the property transfers. */ if (parent->flags & SD_PREFER_SIBLING) tmp->flags |= SD_PREFER_SIBLING; destroy_sched_domain(parent); } else tmp = tmp->parent; } if (sd && sd_degenerate(sd)) { tmp = sd; sd = sd->parent; destroy_sched_domain(tmp); if (sd) sd->child = NULL; } sched_domain_debug(sd, cpu); rq_attach_root(rq, rd); tmp = rq->sd; rcu_assign_pointer(rq->sd, sd); destroy_sched_domains(tmp); update_top_cache_domain(cpu); } /* Setup the mask of cpus configured for isolated domains */ static int __init isolated_cpu_setup(char *str) { int ret; alloc_bootmem_cpumask_var(&cpu_isolated_map); ret = cpulist_parse(str, cpu_isolated_map); if (ret) { pr_err("sched: Error, all isolcpus= values must be between 0 and %d\n", nr_cpu_ids); return 0; } return 1; } __setup("isolcpus=", isolated_cpu_setup); struct s_data { struct sched_domain ** __percpu sd; struct root_domain *rd; }; enum s_alloc { sa_rootdomain, sa_sd, sa_sd_storage, sa_none, }; /* * Build an iteration mask that can exclude certain CPUs from the upwards * domain traversal. * * Asymmetric node setups can result in situations where the domain tree is of * unequal depth, make sure to skip domains that already cover the entire * range. * * In that case build_sched_domains() will have terminated the iteration early * and our sibling sd spans will be empty. Domains should always include the * cpu they're built on, so check that. * */ static void build_group_mask(struct sched_domain *sd, struct sched_group *sg) { const struct cpumask *span = sched_domain_span(sd); struct sd_data *sdd = sd->private; struct sched_domain *sibling; int i; for_each_cpu(i, span) { sibling = *per_cpu_ptr(sdd->sd, i); if (!cpumask_test_cpu(i, sched_domain_span(sibling))) continue; cpumask_set_cpu(i, sched_group_mask(sg)); } } /* * Return the canonical balance cpu for this group, this is the first cpu * of this group that's also in the iteration mask. */ int group_balance_cpu(struct sched_group *sg) { return cpumask_first_and(sched_group_cpus(sg), sched_group_mask(sg)); } static int build_overlap_sched_groups(struct sched_domain *sd, int cpu) { struct sched_group *first = NULL, *last = NULL, *groups = NULL, *sg; const struct cpumask *span = sched_domain_span(sd); struct cpumask *covered = sched_domains_tmpmask; struct sd_data *sdd = sd->private; struct sched_domain *sibling; int i; cpumask_clear(covered); for_each_cpu(i, span) { struct cpumask *sg_span; if (cpumask_test_cpu(i, covered)) continue; sibling = *per_cpu_ptr(sdd->sd, i); /* See the comment near build_group_mask(). */ if (!cpumask_test_cpu(i, sched_domain_span(sibling))) continue; sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(), GFP_KERNEL, cpu_to_node(cpu)); if (!sg) goto fail; sg_span = sched_group_cpus(sg); if (sibling->child) cpumask_copy(sg_span, sched_domain_span(sibling->child)); else cpumask_set_cpu(i, sg_span); cpumask_or(covered, covered, sg_span); sg->sgc = *per_cpu_ptr(sdd->sgc, i); if (atomic_inc_return(&sg->sgc->ref) == 1) build_group_mask(sd, sg); /* * Initialize sgc->capacity such that even if we mess up the * domains and no possible iteration will get us here, we won't * die on a /0 trap. */ sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span); sg->sgc->min_capacity = SCHED_CAPACITY_SCALE; /* * Make sure the first group of this domain contains the * canonical balance cpu. Otherwise the sched_domain iteration * breaks. See update_sg_lb_stats(). */ if ((!groups && cpumask_test_cpu(cpu, sg_span)) || group_balance_cpu(sg) == cpu) groups = sg; if (!first) first = sg; if (last) last->next = sg; last = sg; last->next = first; } sd->groups = groups; return 0; fail: free_sched_groups(first, 0); return -ENOMEM; } static int get_group(int cpu, struct sd_data *sdd, struct sched_group **sg) { struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu); struct sched_domain *child = sd->child; if (child) cpu = cpumask_first(sched_domain_span(child)); if (sg) { *sg = *per_cpu_ptr(sdd->sg, cpu); (*sg)->sgc = *per_cpu_ptr(sdd->sgc, cpu); atomic_set(&(*sg)->sgc->ref, 1); /* for claim_allocations */ } return cpu; } /* * build_sched_groups will build a circular linked list of the groups * covered by the given span, and will set each group's ->cpumask correctly, * and ->cpu_capacity to 0. * * Assumes the sched_domain tree is fully constructed */ static int build_sched_groups(struct sched_domain *sd, int cpu) { struct sched_group *first = NULL, *last = NULL; struct sd_data *sdd = sd->private; const struct cpumask *span = sched_domain_span(sd); struct cpumask *covered; int i; get_group(cpu, sdd, &sd->groups); atomic_inc(&sd->groups->ref); if (cpu != cpumask_first(span)) return 0; lockdep_assert_held(&sched_domains_mutex); covered = sched_domains_tmpmask; cpumask_clear(covered); for_each_cpu(i, span) { struct sched_group *sg; int group, j; if (cpumask_test_cpu(i, covered)) continue; group = get_group(i, sdd, &sg); cpumask_setall(sched_group_mask(sg)); for_each_cpu(j, span) { if (get_group(j, sdd, NULL) != group) continue; cpumask_set_cpu(j, covered); cpumask_set_cpu(j, sched_group_cpus(sg)); } if (!first) first = sg; if (last) last->next = sg; last = sg; } last->next = first; return 0; } /* * Initialize sched groups cpu_capacity. * * cpu_capacity indicates the capacity of sched group, which is used while * distributing the load between different sched groups in a sched domain. * Typically cpu_capacity for all the groups in a sched domain will be same * unless there are asymmetries in the topology. If there are asymmetries, * group having more cpu_capacity will pickup more load compared to the * group having less cpu_capacity. */ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd) { struct sched_group *sg = sd->groups; WARN_ON(!sg); do { int cpu, max_cpu = -1; sg->group_weight = cpumask_weight(sched_group_cpus(sg)); if (!(sd->flags & SD_ASYM_PACKING)) goto next; for_each_cpu(cpu, sched_group_cpus(sg)) { if (max_cpu < 0) max_cpu = cpu; else if (sched_asym_prefer(cpu, max_cpu)) max_cpu = cpu; } sg->asym_prefer_cpu = max_cpu; next: sg = sg->next; } while (sg != sd->groups); if (cpu != group_balance_cpu(sg)) return; update_group_capacity(sd, cpu); } /* * Initializers for schedule domains * Non-inlined to reduce accumulated stack pressure in build_sched_domains() */ static int default_relax_domain_level = -1; int sched_domain_level_max; static int __init setup_relax_domain_level(char *str) { if (kstrtoint(str, 0, &default_relax_domain_level)) pr_warn("Unable to set relax_domain_level\n"); return 1; } __setup("relax_domain_level=", setup_relax_domain_level); static void set_domain_attribute(struct sched_domain *sd, struct sched_domain_attr *attr) { int request; if (!attr || attr->relax_domain_level < 0) { if (default_relax_domain_level < 0) return; else request = default_relax_domain_level; } else request = attr->relax_domain_level; if (request < sd->level) { /* turn off idle balance on this domain */ sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE); } else { /* turn on idle balance on this domain */ sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE); } } static void __sdt_free(const struct cpumask *cpu_map); static int __sdt_alloc(const struct cpumask *cpu_map); static void __free_domain_allocs(struct s_data *d, enum s_alloc what, const struct cpumask *cpu_map) { switch (what) { case sa_rootdomain: if (!atomic_read(&d->rd->refcount)) free_rootdomain(&d->rd->rcu); /* fall through */ case sa_sd: free_percpu(d->sd); /* fall through */ case sa_sd_storage: __sdt_free(cpu_map); /* fall through */ case sa_none: break; } } static enum s_alloc __visit_domain_allocation_hell(struct s_data *d, const struct cpumask *cpu_map) { memset(d, 0, sizeof(*d)); if (__sdt_alloc(cpu_map)) return sa_sd_storage; d->sd = alloc_percpu(struct sched_domain *); if (!d->sd) return sa_sd_storage; d->rd = alloc_rootdomain(); if (!d->rd) return sa_sd; return sa_rootdomain; } /* * NULL the sd_data elements we've used to build the sched_domain and * sched_group structure so that the subsequent __free_domain_allocs() * will not free the data we're using. */ static void claim_allocations(int cpu, struct sched_domain *sd) { struct sd_data *sdd = sd->private; WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd); *per_cpu_ptr(sdd->sd, cpu) = NULL; if (atomic_read(&(*per_cpu_ptr(sdd->sds, cpu))->ref)) *per_cpu_ptr(sdd->sds, cpu) = NULL; if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref)) *per_cpu_ptr(sdd->sg, cpu) = NULL; if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref)) *per_cpu_ptr(sdd->sgc, cpu) = NULL; } #ifdef CONFIG_NUMA static int sched_domains_numa_levels; enum numa_topology_type sched_numa_topology_type; static int *sched_domains_numa_distance; int sched_max_numa_distance; static struct cpumask ***sched_domains_numa_masks; static int sched_domains_curr_level; #endif /* * SD_flags allowed in topology descriptions. * * These flags are purely descriptive of the topology and do not prescribe * behaviour. Behaviour is artificial and mapped in the below sd_init() * function: * * SD_SHARE_CPUCAPACITY - describes SMT topologies * SD_SHARE_PKG_RESOURCES - describes shared caches * SD_NUMA - describes NUMA topologies * SD_SHARE_POWERDOMAIN - describes shared power domain * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies * * Odd one out, which beside describing the topology has a quirk also * prescribes the desired behaviour that goes along with it: * * SD_ASYM_PACKING - describes SMT quirks */ #define TOPOLOGY_SD_FLAGS \ (SD_SHARE_CPUCAPACITY | \ SD_SHARE_PKG_RESOURCES | \ SD_NUMA | \ SD_ASYM_PACKING | \ SD_ASYM_CPUCAPACITY | \ SD_SHARE_POWERDOMAIN) static struct sched_domain * sd_init(struct sched_domain_topology_level *tl, const struct cpumask *cpu_map, struct sched_domain *child, int cpu) { struct sd_data *sdd = &tl->data; struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu); int sd_id, sd_weight, sd_flags = 0; #ifdef CONFIG_NUMA /* * Ugly hack to pass state to sd_numa_mask()... */ sched_domains_curr_level = tl->numa_level; #endif sd_weight = cpumask_weight(tl->mask(cpu)); if (tl->sd_flags) sd_flags = (*tl->sd_flags)(); if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS, "wrong sd_flags in topology description\n")) sd_flags &= ~TOPOLOGY_SD_FLAGS; *sd = (struct sched_domain){ .min_interval = sd_weight, .max_interval = 2*sd_weight, .busy_factor = 32, .imbalance_pct = 125, .cache_nice_tries = 0, .busy_idx = 0, .idle_idx = 0, .newidle_idx = 0, .wake_idx = 0, .forkexec_idx = 0, .flags = 1*SD_LOAD_BALANCE | 1*SD_BALANCE_NEWIDLE | 1*SD_BALANCE_EXEC | 1*SD_BALANCE_FORK | 0*SD_BALANCE_WAKE | 1*SD_WAKE_AFFINE | 0*SD_SHARE_CPUCAPACITY | 0*SD_SHARE_PKG_RESOURCES | 0*SD_SERIALIZE | 0*SD_PREFER_SIBLING | 0*SD_NUMA | sd_flags , .last_balance = jiffies, .balance_interval = sd_weight, .smt_gain = 0, .max_newidle_lb_cost = 0, .next_decay_max_lb_cost = jiffies, .child = child, #ifdef CONFIG_SCHED_DEBUG .name = tl->name, #endif }; cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu)); sd_id = cpumask_first(sched_domain_span(sd)); /* * Convert topological properties into behaviour. */ if (sd->flags & SD_ASYM_CPUCAPACITY) { struct sched_domain *t = sd; for_each_lower_domain(t) t->flags |= SD_BALANCE_WAKE; } if (sd->flags & SD_SHARE_CPUCAPACITY) { sd->flags |= SD_PREFER_SIBLING; sd->imbalance_pct = 110; sd->smt_gain = 1178; /* ~15% */ } else if (sd->flags & SD_SHARE_PKG_RESOURCES) { sd->imbalance_pct = 117; sd->cache_nice_tries = 1; sd->busy_idx = 2; #ifdef CONFIG_NUMA } else if (sd->flags & SD_NUMA) { sd->cache_nice_tries = 2; sd->busy_idx = 3; sd->idle_idx = 2; sd->flags |= SD_SERIALIZE; if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) { sd->flags &= ~(SD_BALANCE_EXEC | SD_BALANCE_FORK | SD_WAKE_AFFINE); } #endif } else { sd->flags |= SD_PREFER_SIBLING; sd->cache_nice_tries = 1; sd->busy_idx = 2; sd->idle_idx = 1; } /* * For all levels sharing cache; connect a sched_domain_shared * instance. */ if (sd->flags & SD_SHARE_PKG_RESOURCES) { sd->shared = *per_cpu_ptr(sdd->sds, sd_id); atomic_inc(&sd->shared->ref); atomic_set(&sd->shared->nr_busy_cpus, sd_weight); } sd->private = sdd; return sd; } /* * Topology list, bottom-up. */ static struct sched_domain_topology_level default_topology[] = { #ifdef CONFIG_SCHED_SMT { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) }, #endif #ifdef CONFIG_SCHED_MC { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) }, #endif { cpu_cpu_mask, SD_INIT_NAME(DIE) }, { NULL, }, }; static struct sched_domain_topology_level *sched_domain_topology = default_topology; #define for_each_sd_topology(tl) \ for (tl = sched_domain_topology; tl->mask; tl++) void set_sched_topology(struct sched_domain_topology_level *tl) { if (WARN_ON_ONCE(sched_smp_initialized)) return; sched_domain_topology = tl; } #ifdef CONFIG_NUMA static const struct cpumask *sd_numa_mask(int cpu) { return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)]; } static void sched_numa_warn(const char *str) { static int done = false; int i,j; if (done) return; done = true; printk(KERN_WARNING "ERROR: %s\n\n", str); for (i = 0; i < nr_node_ids; i++) { printk(KERN_WARNING " "); for (j = 0; j < nr_node_ids; j++) printk(KERN_CONT "%02d ", node_distance(i,j)); printk(KERN_CONT "\n"); } printk(KERN_WARNING "\n"); } bool find_numa_distance(int distance) { int i; if (distance == node_distance(0, 0)) return true; for (i = 0; i < sched_domains_numa_levels; i++) { if (sched_domains_numa_distance[i] == distance) return true; } return false; } /* * A system can have three types of NUMA topology: * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes * NUMA_BACKPLANE: nodes can reach other nodes through a backplane * * The difference between a glueless mesh topology and a backplane * topology lies in whether communication between not directly * connected nodes goes through intermediary nodes (where programs * could run), or through backplane controllers. This affects * placement of programs. * * The type of topology can be discerned with the following tests: * - If the maximum distance between any nodes is 1 hop, the system * is directly connected. * - If for two nodes A and B, located N > 1 hops away from each other, * there is an intermediary node C, which is < N hops away from both * nodes A and B, the system is a glueless mesh. */ static void init_numa_topology_type(void) { int a, b, c, n; n = sched_max_numa_distance; if (sched_domains_numa_levels <= 1) { sched_numa_topology_type = NUMA_DIRECT; return; } for_each_online_node(a) { for_each_online_node(b) { /* Find two nodes furthest removed from each other. */ if (node_distance(a, b) < n) continue; /* Is there an intermediary node between a and b? */ for_each_online_node(c) { if (node_distance(a, c) < n && node_distance(b, c) < n) { sched_numa_topology_type = NUMA_GLUELESS_MESH; return; } } sched_numa_topology_type = NUMA_BACKPLANE; return; } } } static void sched_init_numa(void) { int next_distance, curr_distance = node_distance(0, 0); struct sched_domain_topology_level *tl; int level = 0; int i, j, k; sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL); if (!sched_domains_numa_distance) return; /* * O(nr_nodes^2) deduplicating selection sort -- in order to find the * unique distances in the node_distance() table. * * Assumes node_distance(0,j) includes all distances in * node_distance(i,j) in order to avoid cubic time. */ next_distance = curr_distance; for (i = 0; i < nr_node_ids; i++) { for (j = 0; j < nr_node_ids; j++) { for (k = 0; k < nr_node_ids; k++) { int distance = node_distance(i, k); if (distance > curr_distance && (distance < next_distance || next_distance == curr_distance)) next_distance = distance; /* * While not a strong assumption it would be nice to know * about cases where if node A is connected to B, B is not * equally connected to A. */ if (sched_debug() && node_distance(k, i) != distance) sched_numa_warn("Node-distance not symmetric"); if (sched_debug() && i && !find_numa_distance(distance)) sched_numa_warn("Node-0 not representative"); } if (next_distance != curr_distance) { sched_domains_numa_distance[level++] = next_distance; sched_domains_numa_levels = level; curr_distance = next_distance; } else break; } /* * In case of sched_debug() we verify the above assumption. */ if (!sched_debug()) break; } if (!level) return; /* * 'level' contains the number of unique distances, excluding the * identity distance node_distance(i,i). * * The sched_domains_numa_distance[] array includes the actual distance * numbers. */ /* * Here, we should temporarily reset sched_domains_numa_levels to 0. * If it fails to allocate memory for array sched_domains_numa_masks[][], * the array will contain less then 'level' members. This could be * dangerous when we use it to iterate array sched_domains_numa_masks[][] * in other functions. * * We reset it to 'level' at the end of this function. */ sched_domains_numa_levels = 0; sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL); if (!sched_domains_numa_masks) return; /* * Now for each level, construct a mask per node which contains all * cpus of nodes that are that many hops away from us. */ for (i = 0; i < level; i++) { sched_domains_numa_masks[i] = kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL); if (!sched_domains_numa_masks[i]) return; for (j = 0; j < nr_node_ids; j++) { struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL); if (!mask) return; sched_domains_numa_masks[i][j] = mask; for_each_node(k) { if (node_distance(j, k) > sched_domains_numa_distance[i]) continue; cpumask_or(mask, mask, cpumask_of_node(k)); } } } /* Compute default topology size */ for (i = 0; sched_domain_topology[i].mask; i++); tl = kzalloc((i + level + 1) * sizeof(struct sched_domain_topology_level), GFP_KERNEL); if (!tl) return; /* * Copy the default topology bits.. */ for (i = 0; sched_domain_topology[i].mask; i++) tl[i] = sched_domain_topology[i]; /* * .. and append 'j' levels of NUMA goodness. */ for (j = 0; j < level; i++, j++) { tl[i] = (struct sched_domain_topology_level){ .mask = sd_numa_mask, .sd_flags = cpu_numa_flags, .flags = SDTL_OVERLAP, .numa_level = j, SD_INIT_NAME(NUMA) }; } sched_domain_topology = tl; sched_domains_numa_levels = level; sched_max_numa_distance = sched_domains_numa_distance[level - 1]; init_numa_topology_type(); } static void sched_domains_numa_masks_set(unsigned int cpu) { int node = cpu_to_node(cpu); int i, j; for (i = 0; i < sched_domains_numa_levels; i++) { for (j = 0; j < nr_node_ids; j++) { if (node_distance(j, node) <= sched_domains_numa_distance[i]) cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]); } } } static void sched_domains_numa_masks_clear(unsigned int cpu) { int i, j; for (i = 0; i < sched_domains_numa_levels; i++) { for (j = 0; j < nr_node_ids; j++) cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]); } } #else static inline void sched_init_numa(void) { } static void sched_domains_numa_masks_set(unsigned int cpu) { } static void sched_domains_numa_masks_clear(unsigned int cpu) { } #endif /* CONFIG_NUMA */ static int __sdt_alloc(const struct cpumask *cpu_map) { struct sched_domain_topology_level *tl; int j; for_each_sd_topology(tl) { struct sd_data *sdd = &tl->data; sdd->sd = alloc_percpu(struct sched_domain *); if (!sdd->sd) return -ENOMEM; sdd->sds = alloc_percpu(struct sched_domain_shared *); if (!sdd->sds) return -ENOMEM; sdd->sg = alloc_percpu(struct sched_group *); if (!sdd->sg) return -ENOMEM; sdd->sgc = alloc_percpu(struct sched_group_capacity *); if (!sdd->sgc) return -ENOMEM; for_each_cpu(j, cpu_map) { struct sched_domain *sd; struct sched_domain_shared *sds; struct sched_group *sg; struct sched_group_capacity *sgc; sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(), GFP_KERNEL, cpu_to_node(j)); if (!sd) return -ENOMEM; *per_cpu_ptr(sdd->sd, j) = sd; sds = kzalloc_node(sizeof(struct sched_domain_shared), GFP_KERNEL, cpu_to_node(j)); if (!sds) return -ENOMEM; *per_cpu_ptr(sdd->sds, j) = sds; sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(), GFP_KERNEL, cpu_to_node(j)); if (!sg) return -ENOMEM; sg->next = sg; *per_cpu_ptr(sdd->sg, j) = sg; sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(), GFP_KERNEL, cpu_to_node(j)); if (!sgc) return -ENOMEM; *per_cpu_ptr(sdd->sgc, j) = sgc; } } return 0; } static void __sdt_free(const struct cpumask *cpu_map) { struct sched_domain_topology_level *tl; int j; for_each_sd_topology(tl) { struct sd_data *sdd = &tl->data; for_each_cpu(j, cpu_map) { struct sched_domain *sd; if (sdd->sd) { sd = *per_cpu_ptr(sdd->sd, j); if (sd && (sd->flags & SD_OVERLAP)) free_sched_groups(sd->groups, 0); kfree(*per_cpu_ptr(sdd->sd, j)); } if (sdd->sds) kfree(*per_cpu_ptr(sdd->sds, j)); if (sdd->sg) kfree(*per_cpu_ptr(sdd->sg, j)); if (sdd->sgc) kfree(*per_cpu_ptr(sdd->sgc, j)); } free_percpu(sdd->sd); sdd->sd = NULL; free_percpu(sdd->sds); sdd->sds = NULL; free_percpu(sdd->sg); sdd->sg = NULL; free_percpu(sdd->sgc); sdd->sgc = NULL; } } struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl, const struct cpumask *cpu_map, struct sched_domain_attr *attr, struct sched_domain *child, int cpu) { struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu); if (child) { sd->level = child->level + 1; sched_domain_level_max = max(sched_domain_level_max, sd->level); child->parent = sd; if (!cpumask_subset(sched_domain_span(child), sched_domain_span(sd))) { pr_err("BUG: arch topology borken\n"); #ifdef CONFIG_SCHED_DEBUG pr_err(" the %s domain not a subset of the %s domain\n", child->name, sd->name); #endif /* Fixup, ensure @sd has at least @child cpus. */ cpumask_or(sched_domain_span(sd), sched_domain_span(sd), sched_domain_span(child)); } } set_domain_attribute(sd, attr); return sd; } /* * Build sched domains for a given set of cpus and attach the sched domains * to the individual cpus */ static int build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *attr) { enum s_alloc alloc_state; struct sched_domain *sd; struct s_data d; struct rq *rq = NULL; int i, ret = -ENOMEM; alloc_state = __visit_domain_allocation_hell(&d, cpu_map); if (alloc_state != sa_rootdomain) goto error; /* Set up domains for cpus specified by the cpu_map. */ for_each_cpu(i, cpu_map) { struct sched_domain_topology_level *tl; sd = NULL; for_each_sd_topology(tl) { sd = build_sched_domain(tl, cpu_map, attr, sd, i); if (tl == sched_domain_topology) *per_cpu_ptr(d.sd, i) = sd; if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP)) sd->flags |= SD_OVERLAP; if (cpumask_equal(cpu_map, sched_domain_span(sd))) break; } } /* Build the groups for the domains */ for_each_cpu(i, cpu_map) { for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { sd->span_weight = cpumask_weight(sched_domain_span(sd)); if (sd->flags & SD_OVERLAP) { if (build_overlap_sched_groups(sd, i)) goto error; } else { if (build_sched_groups(sd, i)) goto error; } } } /* Calculate CPU capacity for physical packages and nodes */ for (i = nr_cpumask_bits-1; i >= 0; i--) { if (!cpumask_test_cpu(i, cpu_map)) continue; for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { claim_allocations(i, sd); init_sched_groups_capacity(i, sd); } } /* Attach the domains */ rcu_read_lock(); for_each_cpu(i, cpu_map) { rq = cpu_rq(i); sd = *per_cpu_ptr(d.sd, i); /* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */ if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity)) WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig); cpu_attach_domain(sd, d.rd, i); } rcu_read_unlock(); if (rq && sched_debug_enabled) { pr_info("span: %*pbl (max cpu_capacity = %lu)\n", cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity); } ret = 0; error: __free_domain_allocs(&d, alloc_state, cpu_map); return ret; } static cpumask_var_t *doms_cur; /* current sched domains */ static int ndoms_cur; /* number of sched domains in 'doms_cur' */ static struct sched_domain_attr *dattr_cur; /* attribues of custom domains in 'doms_cur' */ /* * Special case: If a kmalloc of a doms_cur partition (array of * cpumask) fails, then fallback to a single sched domain, * as determined by the single cpumask fallback_doms. */ static cpumask_var_t fallback_doms; /* * arch_update_cpu_topology lets virtualized architectures update the * cpu core maps. It is supposed to return 1 if the topology changed * or 0 if it stayed the same. */ int __weak arch_update_cpu_topology(void) { return 0; } cpumask_var_t *alloc_sched_domains(unsigned int ndoms) { int i; cpumask_var_t *doms; doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL); if (!doms) return NULL; for (i = 0; i < ndoms; i++) { if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) { free_sched_domains(doms, i); return NULL; } } return doms; } void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms) { unsigned int i; for (i = 0; i < ndoms; i++) free_cpumask_var(doms[i]); kfree(doms); } /* * Set up scheduler domains and groups. Callers must hold the hotplug lock. * For now this just excludes isolated cpus, but could be used to * exclude other special cases in the future. */ static int init_sched_domains(const struct cpumask *cpu_map) { int err; arch_update_cpu_topology(); ndoms_cur = 1; doms_cur = alloc_sched_domains(ndoms_cur); if (!doms_cur) doms_cur = &fallback_doms; cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); err = build_sched_domains(doms_cur[0], NULL); register_sched_domain_sysctl(); return err; } /* * Detach sched domains from a group of cpus specified in cpu_map * These cpus will now be attached to the NULL domain */ static void detach_destroy_domains(const struct cpumask *cpu_map) { int i; rcu_read_lock(); for_each_cpu(i, cpu_map) cpu_attach_domain(NULL, &def_root_domain, i); rcu_read_unlock(); } /* handle null as "default" */ static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur, struct sched_domain_attr *new, int idx_new) { struct sched_domain_attr tmp; /* fast path */ if (!new && !cur) return 1; tmp = SD_ATTR_INIT; return !memcmp(cur ? (cur + idx_cur) : &tmp, new ? (new + idx_new) : &tmp, sizeof(struct sched_domain_attr)); } /* * Partition sched domains as specified by the 'ndoms_new' * cpumasks in the array doms_new[] of cpumasks. This compares * doms_new[] to the current sched domain partitioning, doms_cur[]. * It destroys each deleted domain and builds each new domain. * * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'. * The masks don't intersect (don't overlap.) We should setup one * sched domain for each mask. CPUs not in any of the cpumasks will * not be load balanced. If the same cpumask appears both in the * current 'doms_cur' domains and in the new 'doms_new', we can leave * it as it is. * * The passed in 'doms_new' should be allocated using * alloc_sched_domains. This routine takes ownership of it and will * free_sched_domains it when done with it. If the caller failed the * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1, * and partition_sched_domains() will fallback to the single partition * 'fallback_doms', it also forces the domains to be rebuilt. * * If doms_new == NULL it will be replaced with cpu_online_mask. * ndoms_new == 0 is a special case for destroying existing domains, * and it will not create the default domain. * * Call with hotplug lock held */ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[], struct sched_domain_attr *dattr_new) { int i, j, n; int new_topology; mutex_lock(&sched_domains_mutex); /* always unregister in case we don't destroy any domains */ unregister_sched_domain_sysctl(); /* Let architecture update cpu core mappings. */ new_topology = arch_update_cpu_topology(); n = doms_new ? ndoms_new : 0; /* Destroy deleted domains */ for (i = 0; i < ndoms_cur; i++) { for (j = 0; j < n && !new_topology; j++) { if (cpumask_equal(doms_cur[i], doms_new[j]) && dattrs_equal(dattr_cur, i, dattr_new, j)) goto match1; } /* no match - a current sched domain not in new doms_new[] */ detach_destroy_domains(doms_cur[i]); match1: ; } n = ndoms_cur; if (doms_new == NULL) { n = 0; doms_new = &fallback_doms; cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map); WARN_ON_ONCE(dattr_new); } /* Build new domains */ for (i = 0; i < ndoms_new; i++) { for (j = 0; j < n && !new_topology; j++) { if (cpumask_equal(doms_new[i], doms_cur[j]) && dattrs_equal(dattr_new, i, dattr_cur, j)) goto match2; } /* no match - add a new doms_new */ build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL); match2: ; } /* Remember the new sched domains */ if (doms_cur != &fallback_doms) free_sched_domains(doms_cur, ndoms_cur); kfree(dattr_cur); /* kfree(NULL) is safe */ doms_cur = doms_new; dattr_cur = dattr_new; ndoms_cur = ndoms_new; register_sched_domain_sysctl(); mutex_unlock(&sched_domains_mutex); } static int num_cpus_frozen; /* used to mark begin/end of suspend/resume */ /* * Update cpusets according to cpu_active mask. If cpusets are * disabled, cpuset_update_active_cpus() becomes a simple wrapper * around partition_sched_domains(). * * If we come here as part of a suspend/resume, don't touch cpusets because we * want to restore it back to its original state upon resume anyway. */ static void cpuset_cpu_active(void) { if (cpuhp_tasks_frozen) { /* * num_cpus_frozen tracks how many CPUs are involved in suspend * resume sequence. As long as this is not the last online * operation in the resume sequence, just build a single sched * domain, ignoring cpusets. */ num_cpus_frozen--; if (likely(num_cpus_frozen)) { partition_sched_domains(1, NULL, NULL); return; } /* * This is the last CPU online operation. So fall through and * restore the original sched domains by considering the * cpuset configurations. */ } cpuset_update_active_cpus(true); } static int cpuset_cpu_inactive(unsigned int cpu) { unsigned long flags; struct dl_bw *dl_b; bool overflow; int cpus; if (!cpuhp_tasks_frozen) { rcu_read_lock_sched(); dl_b = dl_bw_of(cpu); raw_spin_lock_irqsave(&dl_b->lock, flags); cpus = dl_bw_cpus(cpu); overflow = __dl_overflow(dl_b, cpus, 0, 0); raw_spin_unlock_irqrestore(&dl_b->lock, flags); rcu_read_unlock_sched(); if (overflow) return -EBUSY; cpuset_update_active_cpus(false); } else { num_cpus_frozen++; partition_sched_domains(1, NULL, NULL); } return 0; } int sched_cpu_activate(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; set_cpu_active(cpu, true); if (sched_smp_initialized) { sched_domains_numa_masks_set(cpu); cpuset_cpu_active(); } /* * Put the rq online, if not already. This happens: * * 1) In the early boot process, because we build the real domains * after all cpus have been brought up. * * 2) At runtime, if cpuset_cpu_active() fails to rebuild the * domains. */ raw_spin_lock_irqsave(&rq->lock, flags); if (rq->rd) { BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); set_rq_online(rq); } raw_spin_unlock_irqrestore(&rq->lock, flags); update_max_interval(); return 0; } int sched_cpu_deactivate(unsigned int cpu) { int ret; set_cpu_active(cpu, false); /* * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU * users of this state to go away such that all new such users will * observe it. * * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might * not imply sync_sched(), so wait for both. * * Do sync before park smpboot threads to take care the rcu boost case. */ if (IS_ENABLED(CONFIG_PREEMPT)) synchronize_rcu_mult(call_rcu, call_rcu_sched); else synchronize_rcu(); if (!sched_smp_initialized) return 0; ret = cpuset_cpu_inactive(cpu); if (ret) { set_cpu_active(cpu, true); return ret; } sched_domains_numa_masks_clear(cpu); return 0; } static void sched_rq_cpu_starting(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); rq->calc_load_update = calc_load_update; update_max_interval(); } int sched_cpu_starting(unsigned int cpu) { set_cpu_rq_start_time(cpu); sched_rq_cpu_starting(cpu); return 0; } #ifdef CONFIG_HOTPLUG_CPU int sched_cpu_dying(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; /* Handle pending wakeups and then migrate everything off */ sched_ttwu_pending(); raw_spin_lock_irqsave(&rq->lock, flags); if (rq->rd) { BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); set_rq_offline(rq); } migrate_tasks(rq); BUG_ON(rq->nr_running != 1); raw_spin_unlock_irqrestore(&rq->lock, flags); calc_load_migrate(rq); update_max_interval(); nohz_balance_exit_idle(cpu); hrtick_clear(rq); return 0; } #endif #ifdef CONFIG_SCHED_SMT DEFINE_STATIC_KEY_FALSE(sched_smt_present); static void sched_init_smt(void) { /* * We've enumerated all CPUs and will assume that if any CPU * has SMT siblings, CPU0 will too. */ if (cpumask_weight(cpu_smt_mask(0)) > 1) static_branch_enable(&sched_smt_present); } #else static inline void sched_init_smt(void) { } #endif void __init sched_init_smp(void) { cpumask_var_t non_isolated_cpus; alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL); alloc_cpumask_var(&fallback_doms, GFP_KERNEL); sched_init_numa(); /* * There's no userspace yet to cause hotplug operations; hence all the * cpu masks are stable and all blatant races in the below code cannot * happen. */ mutex_lock(&sched_domains_mutex); init_sched_domains(cpu_active_mask); cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map); if (cpumask_empty(non_isolated_cpus)) cpumask_set_cpu(smp_processor_id(), non_isolated_cpus); mutex_unlock(&sched_domains_mutex); /* Move init over to a non-isolated CPU */ if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0) BUG(); sched_init_granularity(); free_cpumask_var(non_isolated_cpus); init_sched_rt_class(); init_sched_dl_class(); sched_init_smt(); sched_smp_initialized = true; } static int __init migration_init(void) { sched_rq_cpu_starting(smp_processor_id()); return 0; } early_initcall(migration_init); #else void __init sched_init_smp(void) { sched_init_granularity(); } #endif /* CONFIG_SMP */ int in_sched_functions(unsigned long addr) { return in_lock_functions(addr) || (addr >= (unsigned long)__sched_text_start && addr < (unsigned long)__sched_text_end); } #ifdef CONFIG_CGROUP_SCHED /* * Default task group. * Every task in system belongs to this group at bootup. */ struct task_group root_task_group; LIST_HEAD(task_groups); /* Cacheline aligned slab cache for task_group */ static struct kmem_cache *task_group_cache __read_mostly; #endif DECLARE_PER_CPU(cpumask_var_t, load_balance_mask); DECLARE_PER_CPU(cpumask_var_t, select_idle_mask); #define WAIT_TABLE_BITS 8 #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS) static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned; wait_queue_head_t *bit_waitqueue(void *word, int bit) { const int shift = BITS_PER_LONG == 32 ? 5 : 6; unsigned long val = (unsigned long)word << shift | bit; return bit_wait_table + hash_long(val, WAIT_TABLE_BITS); } EXPORT_SYMBOL(bit_waitqueue); void __init sched_init(void) { int i, j; unsigned long alloc_size = 0, ptr; for (i = 0; i < WAIT_TABLE_SIZE; i++) init_waitqueue_head(bit_wait_table + i); #ifdef CONFIG_FAIR_GROUP_SCHED alloc_size += 2 * nr_cpu_ids * sizeof(void **); #endif #ifdef CONFIG_RT_GROUP_SCHED alloc_size += 2 * nr_cpu_ids * sizeof(void **); #endif if (alloc_size) { ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT); #ifdef CONFIG_FAIR_GROUP_SCHED root_task_group.se = (struct sched_entity **)ptr; ptr += nr_cpu_ids * sizeof(void **); root_task_group.cfs_rq = (struct cfs_rq **)ptr; ptr += nr_cpu_ids * sizeof(void **); #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED root_task_group.rt_se = (struct sched_rt_entity **)ptr; ptr += nr_cpu_ids * sizeof(void **); root_task_group.rt_rq = (struct rt_rq **)ptr; ptr += nr_cpu_ids * sizeof(void **); #endif /* CONFIG_RT_GROUP_SCHED */ } #ifdef CONFIG_CPUMASK_OFFSTACK for_each_possible_cpu(i) { per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node( cpumask_size(), GFP_KERNEL, cpu_to_node(i)); per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node( cpumask_size(), GFP_KERNEL, cpu_to_node(i)); } #endif /* CONFIG_CPUMASK_OFFSTACK */ init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime()); init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime()); #ifdef CONFIG_SMP init_defrootdomain(); #endif #ifdef CONFIG_RT_GROUP_SCHED init_rt_bandwidth(&root_task_group.rt_bandwidth, global_rt_period(), global_rt_runtime()); #endif /* CONFIG_RT_GROUP_SCHED */ #ifdef CONFIG_CGROUP_SCHED task_group_cache = KMEM_CACHE(task_group, 0); list_add(&root_task_group.list, &task_groups); INIT_LIST_HEAD(&root_task_group.children); INIT_LIST_HEAD(&root_task_group.siblings); autogroup_init(&init_task); #endif /* CONFIG_CGROUP_SCHED */ for_each_possible_cpu(i) { struct rq *rq; rq = cpu_rq(i); raw_spin_lock_init(&rq->lock); rq->nr_running = 0; rq->calc_load_active = 0; rq->calc_load_update = jiffies + LOAD_FREQ; init_cfs_rq(&rq->cfs); init_rt_rq(&rq->rt); init_dl_rq(&rq->dl); #ifdef CONFIG_FAIR_GROUP_SCHED root_task_group.shares = ROOT_TASK_GROUP_LOAD; INIT_LIST_HEAD(&rq->leaf_cfs_rq_list); rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; /* * How much cpu bandwidth does root_task_group get? * * In case of task-groups formed thr' the cgroup filesystem, it * gets 100% of the cpu resources in the system. This overall * system cpu resource is divided among the tasks of * root_task_group and its child task-groups in a fair manner, * based on each entity's (task or task-group's) weight * (se->load.weight). * * In other words, if root_task_group has 10 tasks of weight * 1024) and two child groups A0 and A1 (of weight 1024 each), * then A0's share of the cpu resource is: * * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33% * * We achieve this by letting root_task_group's tasks sit * directly in rq->cfs (i.e root_task_group->se[] = NULL). */ init_cfs_bandwidth(&root_task_group.cfs_bandwidth); init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL); #endif /* CONFIG_FAIR_GROUP_SCHED */ rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime; #ifdef CONFIG_RT_GROUP_SCHED init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL); #endif for (j = 0; j < CPU_LOAD_IDX_MAX; j++) rq->cpu_load[j] = 0; #ifdef CONFIG_SMP rq->sd = NULL; rq->rd = NULL; rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE; rq->balance_callback = NULL; rq->active_balance = 0; rq->next_balance = jiffies; rq->push_cpu = 0; rq->cpu = i; rq->online = 0; rq->idle_stamp = 0; rq->avg_idle = 2*sysctl_sched_migration_cost; rq->max_idle_balance_cost = sysctl_sched_migration_cost; INIT_LIST_HEAD(&rq->cfs_tasks); rq_attach_root(rq, &def_root_domain); #ifdef CONFIG_NO_HZ_COMMON rq->last_load_update_tick = jiffies; rq->nohz_flags = 0; #endif #ifdef CONFIG_NO_HZ_FULL rq->last_sched_tick = 0; #endif #endif /* CONFIG_SMP */ init_rq_hrtick(rq); atomic_set(&rq->nr_iowait, 0); } set_load_weight(&init_task); /* * The boot idle thread does lazy MMU switching as well: */ atomic_inc(&init_mm.mm_count); enter_lazy_tlb(&init_mm, current); /* * Make us the idle thread. Technically, schedule() should not be * called from this thread, however somewhere below it might be, * but because we are the idle thread, we just pick up running again * when this runqueue becomes "idle". */ init_idle(current, smp_processor_id()); calc_load_update = jiffies + LOAD_FREQ; #ifdef CONFIG_SMP zalloc_cpumask_var(&sched_domains_tmpmask, GFP_NOWAIT); /* May be allocated at isolcpus cmdline parse time */ if (cpu_isolated_map == NULL) zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT); idle_thread_set_boot_cpu(); set_cpu_rq_start_time(smp_processor_id()); #endif init_sched_fair_class(); init_schedstats(); scheduler_running = 1; } #ifdef CONFIG_DEBUG_ATOMIC_SLEEP static inline int preempt_count_equals(int preempt_offset) { int nested = preempt_count() + rcu_preempt_depth(); return (nested == preempt_offset); } void __might_sleep(const char *file, int line, int preempt_offset) { /* * Blocking primitives will set (and therefore destroy) current->state, * since we will exit with TASK_RUNNING make sure we enter with it, * otherwise we will destroy state. */ WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change, "do not call blocking ops when !TASK_RUNNING; " "state=%lx set at [<%p>] %pS\n", current->state, (void *)current->task_state_change, (void *)current->task_state_change); ___might_sleep(file, line, preempt_offset); } EXPORT_SYMBOL(__might_sleep); void ___might_sleep(const char *file, int line, int preempt_offset) { static unsigned long prev_jiffy; /* ratelimiting */ unsigned long preempt_disable_ip; rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */ if ((preempt_count_equals(preempt_offset) && !irqs_disabled() && !is_idle_task(current)) || system_state != SYSTEM_RUNNING || oops_in_progress) return; if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) return; prev_jiffy = jiffies; /* Save this before calling printk(), since that will clobber it */ preempt_disable_ip = get_preempt_disable_ip(current); printk(KERN_ERR "BUG: sleeping function called from invalid context at %s:%d\n", file, line); printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", in_atomic(), irqs_disabled(), current->pid, current->comm); if (task_stack_end_corrupted(current)) printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); debug_show_held_locks(current); if (irqs_disabled()) print_irqtrace_events(current); if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) && !preempt_count_equals(preempt_offset)) { pr_err("Preemption disabled at:"); print_ip_sym(preempt_disable_ip); pr_cont("\n"); } dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } EXPORT_SYMBOL(___might_sleep); #endif #ifdef CONFIG_MAGIC_SYSRQ void normalize_rt_tasks(void) { struct task_struct *g, *p; struct sched_attr attr = { .sched_policy = SCHED_NORMAL, }; read_lock(&tasklist_lock); for_each_process_thread(g, p) { /* * Only normalize user tasks: */ if (p->flags & PF_KTHREAD) continue; p->se.exec_start = 0; schedstat_set(p->se.statistics.wait_start, 0); schedstat_set(p->se.statistics.sleep_start, 0); schedstat_set(p->se.statistics.block_start, 0); if (!dl_task(p) && !rt_task(p)) { /* * Renice negative nice level userspace * tasks back to 0: */ if (task_nice(p) < 0) set_user_nice(p, 0); continue; } __sched_setscheduler(p, &attr, false, false); } read_unlock(&tasklist_lock); } #endif /* CONFIG_MAGIC_SYSRQ */ #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) /* * These functions are only useful for the IA64 MCA handling, or kdb. * * They can only be called when the whole system has been * stopped - every CPU needs to be quiescent, and no scheduling * activity can take place. Using them for anything else would * be a serious bug, and as a result, they aren't even visible * under any other configuration. */ /** * curr_task - return the current task for a given cpu. * @cpu: the processor in question. * * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! * * Return: The current task for @cpu. */ struct task_struct *curr_task(int cpu) { return cpu_curr(cpu); } #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */ #ifdef CONFIG_IA64 /** * set_curr_task - set the current task for a given cpu. * @cpu: the processor in question. * @p: the task pointer to set. * * Description: This function must only be used when non-maskable interrupts * are serviced on a separate stack. It allows the architecture to switch the * notion of the current task on a cpu in a non-blocking manner. This function * must be called with all CPU's synchronized, and interrupts disabled, the * and caller must save the original value of the current task (see * curr_task() above) and restore that value before reenabling interrupts and * re-starting the system. * * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! */ void ia64_set_curr_task(int cpu, struct task_struct *p) { cpu_curr(cpu) = p; } #endif #ifdef CONFIG_CGROUP_SCHED /* task_group_lock serializes the addition/removal of task groups */ static DEFINE_SPINLOCK(task_group_lock); static void sched_free_group(struct task_group *tg) { free_fair_sched_group(tg); free_rt_sched_group(tg); autogroup_free(tg); kmem_cache_free(task_group_cache, tg); } /* allocate runqueue etc for a new task group */ struct task_group *sched_create_group(struct task_group *parent) { struct task_group *tg; tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO); if (!tg) return ERR_PTR(-ENOMEM); if (!alloc_fair_sched_group(tg, parent)) goto err; if (!alloc_rt_sched_group(tg, parent)) goto err; return tg; err: sched_free_group(tg); return ERR_PTR(-ENOMEM); } void sched_online_group(struct task_group *tg, struct task_group *parent) { unsigned long flags; spin_lock_irqsave(&task_group_lock, flags); list_add_rcu(&tg->list, &task_groups); WARN_ON(!parent); /* root should already exist */ tg->parent = parent; INIT_LIST_HEAD(&tg->children); list_add_rcu(&tg->siblings, &parent->children); spin_unlock_irqrestore(&task_group_lock, flags); online_fair_sched_group(tg); } /* rcu callback to free various structures associated with a task group */ static void sched_free_group_rcu(struct rcu_head *rhp) { /* now it should be safe to free those cfs_rqs */ sched_free_group(container_of(rhp, struct task_group, rcu)); } void sched_destroy_group(struct task_group *tg) { /* wait for possible concurrent references to cfs_rqs complete */ call_rcu(&tg->rcu, sched_free_group_rcu); } void sched_offline_group(struct task_group *tg) { unsigned long flags; /* end participation in shares distribution */ unregister_fair_sched_group(tg); spin_lock_irqsave(&task_group_lock, flags); list_del_rcu(&tg->list); list_del_rcu(&tg->siblings); spin_unlock_irqrestore(&task_group_lock, flags); } static void sched_change_group(struct task_struct *tsk, int type) { struct task_group *tg; /* * All callers are synchronized by task_rq_lock(); we do not use RCU * which is pointless here. Thus, we pass "true" to task_css_check() * to prevent lockdep warnings. */ tg = container_of(task_css_check(tsk, cpu_cgrp_id, true), struct task_group, css); tg = autogroup_task_group(tsk, tg); tsk->sched_task_group = tg; #ifdef CONFIG_FAIR_GROUP_SCHED if (tsk->sched_class->task_change_group) tsk->sched_class->task_change_group(tsk, type); else #endif set_task_rq(tsk, task_cpu(tsk)); } /* * Change task's runqueue when it moves between groups. * * The caller of this function should have put the task in its new group by * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect * its new group. */ void sched_move_task(struct task_struct *tsk) { int queued, running; struct rq_flags rf; struct rq *rq; rq = task_rq_lock(tsk, &rf); running = task_current(rq, tsk); queued = task_on_rq_queued(tsk); if (queued) dequeue_task(rq, tsk, DEQUEUE_SAVE | DEQUEUE_MOVE); if (unlikely(running)) put_prev_task(rq, tsk); sched_change_group(tsk, TASK_MOVE_GROUP); if (queued) enqueue_task(rq, tsk, ENQUEUE_RESTORE | ENQUEUE_MOVE); if (unlikely(running)) set_curr_task(rq, tsk); task_rq_unlock(rq, tsk, &rf); } #endif /* CONFIG_CGROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED /* * Ensure that the real time constraints are schedulable. */ static DEFINE_MUTEX(rt_constraints_mutex); /* Must be called with tasklist_lock held */ static inline int tg_has_rt_tasks(struct task_group *tg) { struct task_struct *g, *p; /* * Autogroups do not have RT tasks; see autogroup_create(). */ if (task_group_is_autogroup(tg)) return 0; for_each_process_thread(g, p) { if (rt_task(p) && task_group(p) == tg) return 1; } return 0; } struct rt_schedulable_data { struct task_group *tg; u64 rt_period; u64 rt_runtime; }; static int tg_rt_schedulable(struct task_group *tg, void *data) { struct rt_schedulable_data *d = data; struct task_group *child; unsigned long total, sum = 0; u64 period, runtime; period = ktime_to_ns(tg->rt_bandwidth.rt_period); runtime = tg->rt_bandwidth.rt_runtime; if (tg == d->tg) { period = d->rt_period; runtime = d->rt_runtime; } /* * Cannot have more runtime than the period. */ if (runtime > period && runtime != RUNTIME_INF) return -EINVAL; /* * Ensure we don't starve existing RT tasks. */ if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg)) return -EBUSY; total = to_ratio(period, runtime); /* * Nobody can have more than the global setting allows. */ if (total > to_ratio(global_rt_period(), global_rt_runtime())) return -EINVAL; /* * The sum of our children's runtime should not exceed our own. */ list_for_each_entry_rcu(child, &tg->children, siblings) { period = ktime_to_ns(child->rt_bandwidth.rt_period); runtime = child->rt_bandwidth.rt_runtime; if (child == d->tg) { period = d->rt_period; runtime = d->rt_runtime; } sum += to_ratio(period, runtime); } if (sum > total) return -EINVAL; return 0; } static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime) { int ret; struct rt_schedulable_data data = { .tg = tg, .rt_period = period, .rt_runtime = runtime, }; rcu_read_lock(); ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data); rcu_read_unlock(); return ret; } static int tg_set_rt_bandwidth(struct task_group *tg, u64 rt_period, u64 rt_runtime) { int i, err = 0; /* * Disallowing the root group RT runtime is BAD, it would disallow the * kernel creating (and or operating) RT threads. */ if (tg == &root_task_group && rt_runtime == 0) return -EINVAL; /* No period doesn't make any sense. */ if (rt_period == 0) return -EINVAL; mutex_lock(&rt_constraints_mutex); read_lock(&tasklist_lock); err = __rt_schedulable(tg, rt_period, rt_runtime); if (err) goto unlock; raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock); tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period); tg->rt_bandwidth.rt_runtime = rt_runtime; for_each_possible_cpu(i) { struct rt_rq *rt_rq = tg->rt_rq[i]; raw_spin_lock(&rt_rq->rt_runtime_lock); rt_rq->rt_runtime = rt_runtime; raw_spin_unlock(&rt_rq->rt_runtime_lock); } raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock); unlock: read_unlock(&tasklist_lock); mutex_unlock(&rt_constraints_mutex); return err; } static int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us) { u64 rt_runtime, rt_period; rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period); rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC; if (rt_runtime_us < 0) rt_runtime = RUNTIME_INF; return tg_set_rt_bandwidth(tg, rt_period, rt_runtime); } static long sched_group_rt_runtime(struct task_group *tg) { u64 rt_runtime_us; if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF) return -1; rt_runtime_us = tg->rt_bandwidth.rt_runtime; do_div(rt_runtime_us, NSEC_PER_USEC); return rt_runtime_us; } static int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us) { u64 rt_runtime, rt_period; rt_period = rt_period_us * NSEC_PER_USEC; rt_runtime = tg->rt_bandwidth.rt_runtime; return tg_set_rt_bandwidth(tg, rt_period, rt_runtime); } static long sched_group_rt_period(struct task_group *tg) { u64 rt_period_us; rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period); do_div(rt_period_us, NSEC_PER_USEC); return rt_period_us; } #endif /* CONFIG_RT_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED static int sched_rt_global_constraints(void) { int ret = 0; mutex_lock(&rt_constraints_mutex); read_lock(&tasklist_lock); ret = __rt_schedulable(NULL, 0, 0); read_unlock(&tasklist_lock); mutex_unlock(&rt_constraints_mutex); return ret; } static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk) { /* Don't accept realtime tasks when there is no way for them to run */ if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0) return 0; return 1; } #else /* !CONFIG_RT_GROUP_SCHED */ static int sched_rt_global_constraints(void) { unsigned long flags; int i; raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags); for_each_possible_cpu(i) { struct rt_rq *rt_rq = &cpu_rq(i)->rt; raw_spin_lock(&rt_rq->rt_runtime_lock); rt_rq->rt_runtime = global_rt_runtime(); raw_spin_unlock(&rt_rq->rt_runtime_lock); } raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags); return 0; } #endif /* CONFIG_RT_GROUP_SCHED */ static int sched_dl_global_validate(void) { u64 runtime = global_rt_runtime(); u64 period = global_rt_period(); u64 new_bw = to_ratio(period, runtime); struct dl_bw *dl_b; int cpu, ret = 0; unsigned long flags; /* * Here we want to check the bandwidth not being set to some * value smaller than the currently allocated bandwidth in * any of the root_domains. * * FIXME: Cycling on all the CPUs is overdoing, but simpler than * cycling on root_domains... Discussion on different/better * solutions is welcome! */ for_each_possible_cpu(cpu) { rcu_read_lock_sched(); dl_b = dl_bw_of(cpu); raw_spin_lock_irqsave(&dl_b->lock, flags); if (new_bw < dl_b->total_bw) ret = -EBUSY; raw_spin_unlock_irqrestore(&dl_b->lock, flags); rcu_read_unlock_sched(); if (ret) break; } return ret; } static void sched_dl_do_global(void) { u64 new_bw = -1; struct dl_bw *dl_b; int cpu; unsigned long flags; def_dl_bandwidth.dl_period = global_rt_period(); def_dl_bandwidth.dl_runtime = global_rt_runtime(); if (global_rt_runtime() != RUNTIME_INF) new_bw = to_ratio(global_rt_period(), global_rt_runtime()); /* * FIXME: As above... */ for_each_possible_cpu(cpu) { rcu_read_lock_sched(); dl_b = dl_bw_of(cpu); raw_spin_lock_irqsave(&dl_b->lock, flags); dl_b->bw = new_bw; raw_spin_unlock_irqrestore(&dl_b->lock, flags); rcu_read_unlock_sched(); } } static int sched_rt_global_validate(void) { if (sysctl_sched_rt_period <= 0) return -EINVAL; if ((sysctl_sched_rt_runtime != RUNTIME_INF) && (sysctl_sched_rt_runtime > sysctl_sched_rt_period)) return -EINVAL; return 0; } static void sched_rt_do_global(void) { def_rt_bandwidth.rt_runtime = global_rt_runtime(); def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period()); } int sched_rt_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int old_period, old_runtime; static DEFINE_MUTEX(mutex); int ret; mutex_lock(&mutex); old_period = sysctl_sched_rt_period; old_runtime = sysctl_sched_rt_runtime; ret = proc_dointvec(table, write, buffer, lenp, ppos); if (!ret && write) { ret = sched_rt_global_validate(); if (ret) goto undo; ret = sched_dl_global_validate(); if (ret) goto undo; ret = sched_rt_global_constraints(); if (ret) goto undo; sched_rt_do_global(); sched_dl_do_global(); } if (0) { undo: sysctl_sched_rt_period = old_period; sysctl_sched_rt_runtime = old_runtime; } mutex_unlock(&mutex); return ret; } int sched_rr_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret; static DEFINE_MUTEX(mutex); mutex_lock(&mutex); ret = proc_dointvec(table, write, buffer, lenp, ppos); /* make sure that internally we keep jiffies */ /* also, writing zero resets timeslice to default */ if (!ret && write) { sched_rr_timeslice = sched_rr_timeslice <= 0 ? RR_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice); } mutex_unlock(&mutex); return ret; } #ifdef CONFIG_CGROUP_SCHED static inline struct task_group *css_tg(struct cgroup_subsys_state *css) { return css ? container_of(css, struct task_group, css) : NULL; } static struct cgroup_subsys_state * cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) { struct task_group *parent = css_tg(parent_css); struct task_group *tg; if (!parent) { /* This is early initialization for the top cgroup */ return &root_task_group.css; } tg = sched_create_group(parent); if (IS_ERR(tg)) return ERR_PTR(-ENOMEM); sched_online_group(tg, parent); return &tg->css; } static void cpu_cgroup_css_released(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); sched_offline_group(tg); } static void cpu_cgroup_css_free(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); /* * Relies on the RCU grace period between css_released() and this. */ sched_free_group(tg); } /* * This is called before wake_up_new_task(), therefore we really only * have to set its group bits, all the other stuff does not apply. */ static void cpu_cgroup_fork(struct task_struct *task) { struct rq_flags rf; struct rq *rq; rq = task_rq_lock(task, &rf); sched_change_group(task, TASK_SET_GROUP); task_rq_unlock(rq, task, &rf); } static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) { struct task_struct *task; struct cgroup_subsys_state *css; int ret = 0; cgroup_taskset_for_each(task, css, tset) { #ifdef CONFIG_RT_GROUP_SCHED if (!sched_rt_can_attach(css_tg(css), task)) return -EINVAL; #else /* We don't support RT-tasks being in separate groups */ if (task->sched_class != &fair_sched_class) return -EINVAL; #endif /* * Serialize against wake_up_new_task() such that if its * running, we're sure to observe its full state. */ raw_spin_lock_irq(&task->pi_lock); /* * Avoid calling sched_move_task() before wake_up_new_task() * has happened. This would lead to problems with PELT, due to * move wanting to detach+attach while we're not attached yet. */ if (task->state == TASK_NEW) ret = -EINVAL; raw_spin_unlock_irq(&task->pi_lock); if (ret) break; } return ret; } static void cpu_cgroup_attach(struct cgroup_taskset *tset) { struct task_struct *task; struct cgroup_subsys_state *css; cgroup_taskset_for_each(task, css, tset) sched_move_task(task); } #ifdef CONFIG_FAIR_GROUP_SCHED static int cpu_shares_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 shareval) { return sched_group_set_shares(css_tg(css), scale_load(shareval)); } static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { struct task_group *tg = css_tg(css); return (u64) scale_load_down(tg->shares); } #ifdef CONFIG_CFS_BANDWIDTH static DEFINE_MUTEX(cfs_constraints_mutex); const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */ const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime); static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) { int i, ret = 0, runtime_enabled, runtime_was_enabled; struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; if (tg == &root_task_group) return -EINVAL; /* * Ensure we have at some amount of bandwidth every period. This is * to prevent reaching a state of large arrears when throttled via * entity_tick() resulting in prolonged exit starvation. */ if (quota < min_cfs_quota_period || period < min_cfs_quota_period) return -EINVAL; /* * Likewise, bound things on the otherside by preventing insane quota * periods. This also allows us to normalize in computing quota * feasibility. */ if (period > max_cfs_quota_period) return -EINVAL; /* * Prevent race between setting of cfs_rq->runtime_enabled and * unthrottle_offline_cfs_rqs(). */ get_online_cpus(); mutex_lock(&cfs_constraints_mutex); ret = __cfs_schedulable(tg, period, quota); if (ret) goto out_unlock; runtime_enabled = quota != RUNTIME_INF; runtime_was_enabled = cfs_b->quota != RUNTIME_INF; /* * If we need to toggle cfs_bandwidth_used, off->on must occur * before making related changes, and on->off must occur afterwards */ if (runtime_enabled && !runtime_was_enabled) cfs_bandwidth_usage_inc(); raw_spin_lock_irq(&cfs_b->lock); cfs_b->period = ns_to_ktime(period); cfs_b->quota = quota; __refill_cfs_bandwidth_runtime(cfs_b); /* restart the period timer (if active) to handle new period expiry */ if (runtime_enabled) start_cfs_bandwidth(cfs_b); raw_spin_unlock_irq(&cfs_b->lock); for_each_online_cpu(i) { struct cfs_rq *cfs_rq = tg->cfs_rq[i]; struct rq *rq = cfs_rq->rq; raw_spin_lock_irq(&rq->lock); cfs_rq->runtime_enabled = runtime_enabled; cfs_rq->runtime_remaining = 0; if (cfs_rq->throttled) unthrottle_cfs_rq(cfs_rq); raw_spin_unlock_irq(&rq->lock); } if (runtime_was_enabled && !runtime_enabled) cfs_bandwidth_usage_dec(); out_unlock: mutex_unlock(&cfs_constraints_mutex); put_online_cpus(); return ret; } int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us) { u64 quota, period; period = ktime_to_ns(tg->cfs_bandwidth.period); if (cfs_quota_us < 0) quota = RUNTIME_INF; else quota = (u64)cfs_quota_us * NSEC_PER_USEC; return tg_set_cfs_bandwidth(tg, period, quota); } long tg_get_cfs_quota(struct task_group *tg) { u64 quota_us; if (tg->cfs_bandwidth.quota == RUNTIME_INF) return -1; quota_us = tg->cfs_bandwidth.quota; do_div(quota_us, NSEC_PER_USEC); return quota_us; } int tg_set_cfs_period(struct task_group *tg, long cfs_period_us) { u64 quota, period; period = (u64)cfs_period_us * NSEC_PER_USEC; quota = tg->cfs_bandwidth.quota; return tg_set_cfs_bandwidth(tg, period, quota); } long tg_get_cfs_period(struct task_group *tg) { u64 cfs_period_us; cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period); do_div(cfs_period_us, NSEC_PER_USEC); return cfs_period_us; } static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) { return tg_get_cfs_quota(css_tg(css)); } static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css, struct cftype *cftype, s64 cfs_quota_us) { return tg_set_cfs_quota(css_tg(css), cfs_quota_us); } static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { return tg_get_cfs_period(css_tg(css)); } static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 cfs_period_us) { return tg_set_cfs_period(css_tg(css), cfs_period_us); } struct cfs_schedulable_data { struct task_group *tg; u64 period, quota; }; /* * normalize group quota/period to be quota/max_period * note: units are usecs */ static u64 normalize_cfs_quota(struct task_group *tg, struct cfs_schedulable_data *d) { u64 quota, period; if (tg == d->tg) { period = d->period; quota = d->quota; } else { period = tg_get_cfs_period(tg); quota = tg_get_cfs_quota(tg); } /* note: these should typically be equivalent */ if (quota == RUNTIME_INF || quota == -1) return RUNTIME_INF; return to_ratio(period, quota); } static int tg_cfs_schedulable_down(struct task_group *tg, void *data) { struct cfs_schedulable_data *d = data; struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; s64 quota = 0, parent_quota = -1; if (!tg->parent) { quota = RUNTIME_INF; } else { struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth; quota = normalize_cfs_quota(tg, d); parent_quota = parent_b->hierarchical_quota; /* * ensure max(child_quota) <= parent_quota, inherit when no * limit is set */ if (quota == RUNTIME_INF) quota = parent_quota; else if (parent_quota != RUNTIME_INF && quota > parent_quota) return -EINVAL; } cfs_b->hierarchical_quota = quota; return 0; } static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota) { int ret; struct cfs_schedulable_data data = { .tg = tg, .period = period, .quota = quota, }; if (quota != RUNTIME_INF) { do_div(data.period, NSEC_PER_USEC); do_div(data.quota, NSEC_PER_USEC); } rcu_read_lock(); ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data); rcu_read_unlock(); return ret; } static int cpu_stats_show(struct seq_file *sf, void *v) { struct task_group *tg = css_tg(seq_css(sf)); struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods); seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled); seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time); return 0; } #endif /* CONFIG_CFS_BANDWIDTH */ #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED static int cpu_rt_runtime_write(struct cgroup_subsys_state *css, struct cftype *cft, s64 val) { return sched_group_set_rt_runtime(css_tg(css), val); } static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css, struct cftype *cft) { return sched_group_rt_runtime(css_tg(css)); } static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css, struct cftype *cftype, u64 rt_period_us) { return sched_group_set_rt_period(css_tg(css), rt_period_us); } static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css, struct cftype *cft) { return sched_group_rt_period(css_tg(css)); } #endif /* CONFIG_RT_GROUP_SCHED */ static struct cftype cpu_files[] = { #ifdef CONFIG_FAIR_GROUP_SCHED { .name = "shares", .read_u64 = cpu_shares_read_u64, .write_u64 = cpu_shares_write_u64, }, #endif #ifdef CONFIG_CFS_BANDWIDTH { .name = "cfs_quota_us", .read_s64 = cpu_cfs_quota_read_s64, .write_s64 = cpu_cfs_quota_write_s64, }, { .name = "cfs_period_us", .read_u64 = cpu_cfs_period_read_u64, .write_u64 = cpu_cfs_period_write_u64, }, { .name = "stat", .seq_show = cpu_stats_show, }, #endif #ifdef CONFIG_RT_GROUP_SCHED { .name = "rt_runtime_us", .read_s64 = cpu_rt_runtime_read, .write_s64 = cpu_rt_runtime_write, }, { .name = "rt_period_us", .read_u64 = cpu_rt_period_read_uint, .write_u64 = cpu_rt_period_write_uint, }, #endif { } /* terminate */ }; struct cgroup_subsys cpu_cgrp_subsys = { .css_alloc = cpu_cgroup_css_alloc, .css_released = cpu_cgroup_css_released, .css_free = cpu_cgroup_css_free, .fork = cpu_cgroup_fork, .can_attach = cpu_cgroup_can_attach, .attach = cpu_cgroup_attach, .legacy_cftypes = cpu_files, .early_init = true, }; #endif /* CONFIG_CGROUP_SCHED */ void dump_cpu_task(int cpu) { pr_info("Task dump for CPU %d:\n", cpu); sched_show_task(cpu_curr(cpu)); } /* * Nice levels are multiplicative, with a gentle 10% change for every * nice level changed. I.e. when a CPU-bound task goes from nice 0 to * nice 1, it will get ~10% less CPU time than another CPU-bound task * that remained on nice 0. * * The "10% effect" is relative and cumulative: from _any_ nice level, * if you go up 1 level, it's -10% CPU usage, if you go down 1 level * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25. * If a task goes up by ~10% and another task goes down by ~10% then * the relative distance between them is ~25%.) */ const int sched_prio_to_weight[40] = { /* -20 */ 88761, 71755, 56483, 46273, 36291, /* -15 */ 29154, 23254, 18705, 14949, 11916, /* -10 */ 9548, 7620, 6100, 4904, 3906, /* -5 */ 3121, 2501, 1991, 1586, 1277, /* 0 */ 1024, 820, 655, 526, 423, /* 5 */ 335, 272, 215, 172, 137, /* 10 */ 110, 87, 70, 56, 45, /* 15 */ 36, 29, 23, 18, 15, }; /* * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated. * * In cases where the weight does not change often, we can use the * precalculated inverse to speed up arithmetics by turning divisions * into multiplications: */ const u32 sched_prio_to_wmult[40] = { /* -20 */ 48388, 59856, 76040, 92818, 118348, /* -15 */ 147320, 184698, 229616, 287308, 360437, /* -10 */ 449829, 563644, 704093, 875809, 1099582, /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326, /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587, /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126, /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717, /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, };