/* * Generic entry point for the idle threads */ #include <linux/sched.h> #include <linux/cpu.h> #include <linux/cpuidle.h> #include <linux/cpuhotplug.h> #include <linux/tick.h> #include <linux/mm.h> #include <linux/stackprotector.h> #include <linux/suspend.h> #include <asm/tlb.h> #include <trace/events/power.h> #include "sched.h" /** * sched_idle_set_state - Record idle state for the current CPU. * @idle_state: State to record. */ void sched_idle_set_state(struct cpuidle_state *idle_state) { idle_set_state(this_rq(), idle_state); } static int __read_mostly cpu_idle_force_poll; void cpu_idle_poll_ctrl(bool enable) { if (enable) { cpu_idle_force_poll++; } else { cpu_idle_force_poll--; WARN_ON_ONCE(cpu_idle_force_poll < 0); } } #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP static int __init cpu_idle_poll_setup(char *__unused) { cpu_idle_force_poll = 1; return 1; } __setup("nohlt", cpu_idle_poll_setup); static int __init cpu_idle_nopoll_setup(char *__unused) { cpu_idle_force_poll = 0; return 1; } __setup("hlt", cpu_idle_nopoll_setup); #endif static inline int cpu_idle_poll(void) { rcu_idle_enter(); trace_cpu_idle_rcuidle(0, smp_processor_id()); local_irq_enable(); stop_critical_timings(); while (!tif_need_resched() && (cpu_idle_force_poll || tick_check_broadcast_expired())) cpu_relax(); start_critical_timings(); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); rcu_idle_exit(); return 1; } /* Weak implementations for optional arch specific functions */ void __weak arch_cpu_idle_prepare(void) { } void __weak arch_cpu_idle_enter(void) { } void __weak arch_cpu_idle_exit(void) { } void __weak arch_cpu_idle_dead(void) { } void __weak arch_cpu_idle(void) { cpu_idle_force_poll = 1; local_irq_enable(); } /** * default_idle_call - Default CPU idle routine. * * To use when the cpuidle framework cannot be used. */ void default_idle_call(void) { if (current_clr_polling_and_test()) { local_irq_enable(); } else { stop_critical_timings(); arch_cpu_idle(); start_critical_timings(); } } static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, int next_state) { /* * The idle task must be scheduled, it is pointless to go to idle, just * update no idle residency and return. */ if (current_clr_polling_and_test()) { dev->last_residency = 0; local_irq_enable(); return -EBUSY; } /* * Enter the idle state previously returned by the governor decision. * This function will block until an interrupt occurs and will take * care of re-enabling the local interrupts */ return cpuidle_enter(drv, dev, next_state); } /** * cpuidle_idle_call - the main idle function * * NOTE: no locks or semaphores should be used here * * On archs that support TIF_POLLING_NRFLAG, is called with polling * set, and it returns with polling set. If it ever stops polling, it * must clear the polling bit. */ static void cpuidle_idle_call(void) { struct cpuidle_device *dev = cpuidle_get_device(); struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); int next_state, entered_state; /* * Check if the idle task must be rescheduled. If it is the * case, exit the function after re-enabling the local irq. */ if (need_resched()) { local_irq_enable(); return; } /* * Tell the RCU framework we are entering an idle section, * so no more rcu read side critical sections and one more * step to the grace period */ rcu_idle_enter(); if (cpuidle_not_available(drv, dev)) { default_idle_call(); goto exit_idle; } /* * Suspend-to-idle ("freeze") is a system state in which all user space * has been frozen, all I/O devices have been suspended and the only * activity happens here and in iterrupts (if any). In that case bypass * the cpuidle governor and go stratight for the deepest idle state * available. Possibly also suspend the local tick and the entire * timekeeping to prevent timer interrupts from kicking us out of idle * until a proper wakeup interrupt happens. */ if (idle_should_freeze()) { entered_state = cpuidle_enter_freeze(drv, dev); if (entered_state > 0) { local_irq_enable(); goto exit_idle; } next_state = cpuidle_find_deepest_state(drv, dev); call_cpuidle(drv, dev, next_state); } else { /* * Ask the cpuidle framework to choose a convenient idle state. */ next_state = cpuidle_select(drv, dev); entered_state = call_cpuidle(drv, dev, next_state); /* * Give the governor an opportunity to reflect on the outcome */ cpuidle_reflect(dev, entered_state); } exit_idle: __current_set_polling(); /* * It is up to the idle functions to reenable local interrupts */ if (WARN_ON_ONCE(irqs_disabled())) local_irq_enable(); rcu_idle_exit(); } /* * Generic idle loop implementation * * Called with polling cleared. */ static void cpu_idle_loop(void) { while (1) { /* * If the arch has a polling bit, we maintain an invariant: * * Our polling bit is clear if we're not scheduled (i.e. if * rq->curr != rq->idle). This means that, if rq->idle has * the polling bit set, then setting need_resched is * guaranteed to cause the cpu to reschedule. */ __current_set_polling(); quiet_vmstat(); tick_nohz_idle_enter(); while (!need_resched()) { check_pgt_cache(); rmb(); if (cpu_is_offline(smp_processor_id())) { cpuhp_report_idle_dead(); arch_cpu_idle_dead(); } local_irq_disable(); arch_cpu_idle_enter(); /* * In poll mode we reenable interrupts and spin. * * Also if we detected in the wakeup from idle * path that the tick broadcast device expired * for us, we don't want to go deep idle as we * know that the IPI is going to arrive right * away */ if (cpu_idle_force_poll || tick_check_broadcast_expired()) cpu_idle_poll(); else cpuidle_idle_call(); arch_cpu_idle_exit(); } /* * Since we fell out of the loop above, we know * TIF_NEED_RESCHED must be set, propagate it into * PREEMPT_NEED_RESCHED. * * This is required because for polling idle loops we will * not have had an IPI to fold the state for us. */ preempt_set_need_resched(); tick_nohz_idle_exit(); __current_clr_polling(); /* * We promise to call sched_ttwu_pending and reschedule * if need_resched is set while polling is set. That * means that clearing polling needs to be visible * before doing these things. */ smp_mb__after_atomic(); sched_ttwu_pending(); schedule_preempt_disabled(); } } void cpu_startup_entry(enum cpuhp_state state) { /* * This #ifdef needs to die, but it's too late in the cycle to * make this generic (arm and sh have never invoked the canary * init for the non boot cpus!). Will be fixed in 3.11 */ #ifdef CONFIG_X86 /* * If we're the non-boot CPU, nothing set the stack canary up * for us. The boot CPU already has it initialized but no harm * in doing it again. This is a good place for updating it, as * we wont ever return from this function (so the invalid * canaries already on the stack wont ever trigger). */ boot_init_stack_canary(); #endif arch_cpu_idle_prepare(); cpuhp_online_idle(state); cpu_idle_loop(); }