diff options
Diffstat (limited to 'kernel/events/core.c')
| -rw-r--r-- | kernel/events/core.c | 1199 |
1 files changed, 599 insertions, 600 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 06ae52e99ac2..5946460b2425 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -49,8 +49,6 @@ #include <asm/irq_regs.h> -static struct workqueue_struct *perf_wq; - typedef int (*remote_function_f)(void *); struct remote_function_call { @@ -126,44 +124,181 @@ static int cpu_function_call(int cpu, remote_function_f func, void *info) return data.ret; } -static void event_function_call(struct perf_event *event, - int (*active)(void *), - void (*inactive)(void *), - void *data) +static inline struct perf_cpu_context * +__get_cpu_context(struct perf_event_context *ctx) +{ + return this_cpu_ptr(ctx->pmu->pmu_cpu_context); +} + +static void perf_ctx_lock(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) +{ + raw_spin_lock(&cpuctx->ctx.lock); + if (ctx) + raw_spin_lock(&ctx->lock); +} + +static void perf_ctx_unlock(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) +{ + if (ctx) + raw_spin_unlock(&ctx->lock); + raw_spin_unlock(&cpuctx->ctx.lock); +} + +#define TASK_TOMBSTONE ((void *)-1L) + +static bool is_kernel_event(struct perf_event *event) +{ + return READ_ONCE(event->owner) == TASK_TOMBSTONE; +} + +/* + * On task ctx scheduling... + * + * When !ctx->nr_events a task context will not be scheduled. This means + * we can disable the scheduler hooks (for performance) without leaving + * pending task ctx state. + * + * This however results in two special cases: + * + * - removing the last event from a task ctx; this is relatively straight + * forward and is done in __perf_remove_from_context. + * + * - adding the first event to a task ctx; this is tricky because we cannot + * rely on ctx->is_active and therefore cannot use event_function_call(). + * See perf_install_in_context(). + * + * This is because we need a ctx->lock serialized variable (ctx->is_active) + * to reliably determine if a particular task/context is scheduled in. The + * task_curr() use in task_function_call() is racy in that a remote context + * switch is not a single atomic operation. + * + * As is, the situation is 'safe' because we set rq->curr before we do the + * actual context switch. This means that task_curr() will fail early, but + * we'll continue spinning on ctx->is_active until we've passed + * perf_event_task_sched_out(). + * + * Without this ctx->lock serialized variable we could have race where we find + * the task (and hence the context) would not be active while in fact they are. + * + * If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set. + */ + +typedef void (*event_f)(struct perf_event *, struct perf_cpu_context *, + struct perf_event_context *, void *); + +struct event_function_struct { + struct perf_event *event; + event_f func; + void *data; +}; + +static int event_function(void *info) +{ + struct event_function_struct *efs = info; + struct perf_event *event = efs->event; + struct perf_event_context *ctx = event->ctx; + struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + struct perf_event_context *task_ctx = cpuctx->task_ctx; + int ret = 0; + + WARN_ON_ONCE(!irqs_disabled()); + + perf_ctx_lock(cpuctx, task_ctx); + /* + * Since we do the IPI call without holding ctx->lock things can have + * changed, double check we hit the task we set out to hit. + */ + if (ctx->task) { + if (ctx->task != current) { + ret = -EAGAIN; + goto unlock; + } + + /* + * We only use event_function_call() on established contexts, + * and event_function() is only ever called when active (or + * rather, we'll have bailed in task_function_call() or the + * above ctx->task != current test), therefore we must have + * ctx->is_active here. + */ + WARN_ON_ONCE(!ctx->is_active); + /* + * And since we have ctx->is_active, cpuctx->task_ctx must + * match. + */ + WARN_ON_ONCE(task_ctx != ctx); + } else { + WARN_ON_ONCE(&cpuctx->ctx != ctx); + } + + efs->func(event, cpuctx, ctx, efs->data); +unlock: + perf_ctx_unlock(cpuctx, task_ctx); + + return ret; +} + +static void event_function_local(struct perf_event *event, event_f func, void *data) +{ + struct event_function_struct efs = { + .event = event, + .func = func, + .data = data, + }; + + int ret = event_function(&efs); + WARN_ON_ONCE(ret); +} + +static void event_function_call(struct perf_event *event, event_f func, void *data) { struct perf_event_context *ctx = event->ctx; - struct task_struct *task = ctx->task; + struct task_struct *task = READ_ONCE(ctx->task); /* verified in event_function */ + struct event_function_struct efs = { + .event = event, + .func = func, + .data = data, + }; + + if (!event->parent) { + /* + * If this is a !child event, we must hold ctx::mutex to + * stabilize the the event->ctx relation. See + * perf_event_ctx_lock(). + */ + lockdep_assert_held(&ctx->mutex); + } if (!task) { - cpu_function_call(event->cpu, active, data); + cpu_function_call(event->cpu, event_function, &efs); return; } again: - if (!task_function_call(task, active, data)) + if (task == TASK_TOMBSTONE) + return; + + if (!task_function_call(task, event_function, &efs)) return; raw_spin_lock_irq(&ctx->lock); - if (ctx->is_active) { - /* - * Reload the task pointer, it might have been changed by - * a concurrent perf_event_context_sched_out(). - */ - task = ctx->task; - raw_spin_unlock_irq(&ctx->lock); - goto again; + /* + * Reload the task pointer, it might have been changed by + * a concurrent perf_event_context_sched_out(). + */ + task = ctx->task; + if (task != TASK_TOMBSTONE) { + if (ctx->is_active) { + raw_spin_unlock_irq(&ctx->lock); + goto again; + } + func(event, NULL, ctx, data); } - inactive(data); raw_spin_unlock_irq(&ctx->lock); } -#define EVENT_OWNER_KERNEL ((void *) -1) - -static bool is_kernel_event(struct perf_event *event) -{ - return event->owner == EVENT_OWNER_KERNEL; -} - #define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\ PERF_FLAG_FD_OUTPUT |\ PERF_FLAG_PID_CGROUP |\ @@ -368,28 +503,6 @@ static inline u64 perf_event_clock(struct perf_event *event) return event->clock(); } -static inline struct perf_cpu_context * -__get_cpu_context(struct perf_event_context *ctx) -{ - return this_cpu_ptr(ctx->pmu->pmu_cpu_context); -} - -static void perf_ctx_lock(struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx) -{ - raw_spin_lock(&cpuctx->ctx.lock); - if (ctx) - raw_spin_lock(&ctx->lock); -} - -static void perf_ctx_unlock(struct perf_cpu_context *cpuctx, - struct perf_event_context *ctx) -{ - if (ctx) - raw_spin_unlock(&ctx->lock); - raw_spin_unlock(&cpuctx->ctx.lock); -} - #ifdef CONFIG_CGROUP_PERF static inline bool @@ -579,13 +692,7 @@ static inline void perf_cgroup_sched_out(struct task_struct *task, * we are holding the rcu lock */ cgrp1 = perf_cgroup_from_task(task, NULL); - - /* - * next is NULL when called from perf_event_enable_on_exec() - * that will systematically cause a cgroup_switch() - */ - if (next) - cgrp2 = perf_cgroup_from_task(next, NULL); + cgrp2 = perf_cgroup_from_task(next, NULL); /* * only schedule out current cgroup events if we know @@ -611,8 +718,6 @@ static inline void perf_cgroup_sched_in(struct task_struct *prev, * we are holding the rcu lock */ cgrp1 = perf_cgroup_from_task(task, NULL); - - /* prev can never be NULL */ cgrp2 = perf_cgroup_from_task(prev, NULL); /* @@ -917,7 +1022,7 @@ static void put_ctx(struct perf_event_context *ctx) if (atomic_dec_and_test(&ctx->refcount)) { if (ctx->parent_ctx) put_ctx(ctx->parent_ctx); - if (ctx->task) + if (ctx->task && ctx->task != TASK_TOMBSTONE) put_task_struct(ctx->task); call_rcu(&ctx->rcu_head, free_ctx); } @@ -934,9 +1039,8 @@ static void put_ctx(struct perf_event_context *ctx) * perf_event_context::mutex nests and those are: * * - perf_event_exit_task_context() [ child , 0 ] - * __perf_event_exit_task() - * sync_child_event() - * put_event() [ parent, 1 ] + * perf_event_exit_event() + * put_event() [ parent, 1 ] * * - perf_event_init_context() [ parent, 0 ] * inherit_task_group() @@ -979,8 +1083,8 @@ static void put_ctx(struct perf_event_context *ctx) * Lock order: * task_struct::perf_event_mutex * perf_event_context::mutex - * perf_event_context::lock * perf_event::child_mutex; + * perf_event_context::lock * perf_event::mmap_mutex * mmap_sem */ @@ -1078,6 +1182,7 @@ static u64 primary_event_id(struct perf_event *event) /* * Get the perf_event_context for a task and lock it. + * * This has to cope with with the fact that until it is locked, * the context could get moved to another task. */ @@ -1118,9 +1223,12 @@ retry: goto retry; } - if (!atomic_inc_not_zero(&ctx->refcount)) { + if (ctx->task == TASK_TOMBSTONE || + !atomic_inc_not_zero(&ctx->refcount)) { raw_spin_unlock(&ctx->lock); ctx = NULL; + } else { + WARN_ON_ONCE(ctx->task != task); } } rcu_read_unlock(); @@ -1246,6 +1354,8 @@ ctx_group_list(struct perf_event *event, struct perf_event_context *ctx) static void list_add_event(struct perf_event *event, struct perf_event_context *ctx) { + lockdep_assert_held(&ctx->lock); + WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT); event->attach_state |= PERF_ATTACH_CONTEXT; @@ -1448,11 +1558,14 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) if (is_cgroup_event(event)) { ctx->nr_cgroups--; + /* + * Because cgroup events are always per-cpu events, this will + * always be called from the right CPU. + */ cpuctx = __get_cpu_context(ctx); /* - * if there are no more cgroup events - * then cler cgrp to avoid stale pointer - * in update_cgrp_time_from_cpuctx() + * If there are no more cgroup events then clear cgrp to avoid + * stale pointer in update_cgrp_time_from_cpuctx(). */ if (!ctx->nr_cgroups) cpuctx->cgrp = NULL; @@ -1530,45 +1643,11 @@ out: perf_event__header_size(tmp); } -/* - * User event without the task. - */ static bool is_orphaned_event(struct perf_event *event) { - return event && !is_kernel_event(event) && !event->owner; + return event->state == PERF_EVENT_STATE_EXIT; } -/* - * Event has a parent but parent's task finished and it's - * alive only because of children holding refference. - */ -static bool is_orphaned_child(struct perf_event *event) -{ - return is_orphaned_event(event->parent); -} - -static void orphans_remove_work(struct work_struct *work); - -static void schedule_orphans_remove(struct perf_event_context *ctx) -{ - if (!ctx->task || ctx->orphans_remove_sched || !perf_wq) - return; - - if (queue_delayed_work(perf_wq, &ctx->orphans_remove, 1)) { - get_ctx(ctx); - ctx->orphans_remove_sched = true; - } -} - -static int __init perf_workqueue_init(void) -{ - perf_wq = create_singlethread_workqueue("perf"); - WARN(!perf_wq, "failed to create perf workqueue\n"); - return perf_wq ? 0 : -1; -} - -core_initcall(perf_workqueue_init); - static inline int pmu_filter_match(struct perf_event *event) { struct pmu *pmu = event->pmu; @@ -1629,9 +1708,6 @@ event_sched_out(struct perf_event *event, if (event->attr.exclusive || !cpuctx->active_oncpu) cpuctx->exclusive = 0; - if (is_orphaned_child(event)) - schedule_orphans_remove(ctx); - perf_pmu_enable(event->pmu); } @@ -1655,21 +1731,8 @@ group_sched_out(struct perf_event *group_event, cpuctx->exclusive = 0; } -struct remove_event { - struct perf_event *event; - bool detach_group; -}; - -static void ___perf_remove_from_context(void *info) -{ - struct remove_event *re = info; - struct perf_event *event = re->event; - struct perf_event_context *ctx = event->ctx; - - if (re->detach_group) - perf_group_detach(event); - list_del_event(event, ctx); -} +#define DETACH_GROUP 0x01UL +#define DETACH_STATE 0x02UL /* * Cross CPU call to remove a performance event @@ -1677,33 +1740,33 @@ static void ___perf_remove_from_context(void *info) * We disable the event on the hardware level first. After that we * remove it from the context list. */ -static int __perf_remove_from_context(void *info) +static void +__perf_remove_from_context(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct remove_event *re = info; - struct perf_event *event = re->event; - struct perf_event_context *ctx = event->ctx; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + unsigned long flags = (unsigned long)info; - raw_spin_lock(&ctx->lock); event_sched_out(event, cpuctx, ctx); - if (re->detach_group) + if (flags & DETACH_GROUP) perf_group_detach(event); list_del_event(event, ctx); - if (!ctx->nr_events && cpuctx->task_ctx == ctx) { + if (flags & DETACH_STATE) + event->state = PERF_EVENT_STATE_EXIT; + + if (!ctx->nr_events && ctx->is_active) { ctx->is_active = 0; - cpuctx->task_ctx = NULL; + if (ctx->task) { + WARN_ON_ONCE(cpuctx->task_ctx != ctx); + cpuctx->task_ctx = NULL; + } } - raw_spin_unlock(&ctx->lock); - - return 0; } /* * Remove the event from a task's (or a CPU's) list of events. * - * CPU events are removed with a smp call. For task events we only - * call when the task is on a CPU. - * * If event->ctx is a cloned context, callers must make sure that * every task struct that event->ctx->task could possibly point to * remains valid. This is OK when called from perf_release since @@ -1711,73 +1774,32 @@ static int __perf_remove_from_context(void *info) * When called from perf_event_exit_task, it's OK because the * context has been detached from its task. */ -static void perf_remove_from_context(struct perf_event *event, bool detach_group) +static void perf_remove_from_context(struct perf_event *event, unsigned long flags) { - struct perf_event_context *ctx = event->ctx; - struct remove_event re = { - .event = event, - .detach_group = detach_group, - }; + lockdep_assert_held(&event->ctx->mutex); - lockdep_assert_held(&ctx->mutex); - - event_function_call(event, __perf_remove_from_context, - ___perf_remove_from_context, &re); + event_function_call(event, __perf_remove_from_context, (void *)flags); } /* * Cross CPU call to disable a performance event */ -int __perf_event_disable(void *info) -{ - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); - - /* - * If this is a per-task event, need to check whether this - * event's task is the current task on this cpu. - * - * Can trigger due to concurrent perf_event_context_sched_out() - * flipping contexts around. - */ - if (ctx->task && cpuctx->task_ctx != ctx) - return -EINVAL; - - raw_spin_lock(&ctx->lock); - - /* - * If the event is on, turn it off. - * If it is in error state, leave it in error state. - */ - if (event->state >= PERF_EVENT_STATE_INACTIVE) { - update_context_time(ctx); - update_cgrp_time_from_event(event); - update_group_times(event); - if (event == event->group_leader) - group_sched_out(event, cpuctx, ctx); - else - event_sched_out(event, cpuctx, ctx); - event->state = PERF_EVENT_STATE_OFF; - } - - raw_spin_unlock(&ctx->lock); - - return 0; -} - -void ___perf_event_disable(void *info) +static void __perf_event_disable(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct perf_event *event = info; + if (event->state < PERF_EVENT_STATE_INACTIVE) + return; - /* - * Since we have the lock this context can't be scheduled - * in, so we can change the state safely. - */ - if (event->state == PERF_EVENT_STATE_INACTIVE) { - update_group_times(event); - event->state = PERF_EVENT_STATE_OFF; - } + update_context_time(ctx); + update_cgrp_time_from_event(event); + update_group_times(event); + if (event == event->group_leader) + group_sched_out(event, cpuctx, ctx); + else + event_sched_out(event, cpuctx, ctx); + event->state = PERF_EVENT_STATE_OFF; } /* @@ -1788,7 +1810,8 @@ void ___perf_event_disable(void *info) * remains valid. This condition is satisifed when called through * perf_event_for_each_child or perf_event_for_each because they * hold the top-level event's child_mutex, so any descendant that - * goes to exit will block in sync_child_event. + * goes to exit will block in perf_event_exit_event(). + * * When called from perf_pending_event it's OK because event->ctx * is the current context on this CPU and preemption is disabled, * hence we can't get into perf_event_task_sched_out for this context. @@ -1804,8 +1827,12 @@ static void _perf_event_disable(struct perf_event *event) } raw_spin_unlock_irq(&ctx->lock); - event_function_call(event, __perf_event_disable, - ___perf_event_disable, event); + event_function_call(event, __perf_event_disable, NULL); +} + +void perf_event_disable_local(struct perf_event *event) +{ + event_function_local(event, __perf_event_disable, NULL); } /* @@ -1918,9 +1945,6 @@ event_sched_in(struct perf_event *event, if (event->attr.exclusive) cpuctx->exclusive = 1; - if (is_orphaned_child(event)) - schedule_orphans_remove(ctx); - out: perf_pmu_enable(event->pmu); @@ -2039,7 +2063,8 @@ static void add_event_to_ctx(struct perf_event *event, event->tstamp_stopped = tstamp; } -static void task_ctx_sched_out(struct perf_event_context *ctx); +static void task_ctx_sched_out(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx); static void ctx_sched_in(struct perf_event_context *ctx, struct perf_cpu_context *cpuctx, @@ -2058,16 +2083,15 @@ static void perf_event_sched_in(struct perf_cpu_context *cpuctx, ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task); } -static void ___perf_install_in_context(void *info) +static void ctx_resched(struct perf_cpu_context *cpuctx, + struct perf_event_context *task_ctx) { - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; - - /* - * Since the task isn't running, its safe to add the event, us holding - * the ctx->lock ensures the task won't get scheduled in. - */ - add_event_to_ctx(event, ctx); + perf_pmu_disable(cpuctx->ctx.pmu); + if (task_ctx) + task_ctx_sched_out(cpuctx, task_ctx); + cpu_ctx_sched_out(cpuctx, EVENT_ALL); + perf_event_sched_in(cpuctx, task_ctx, current); + perf_pmu_enable(cpuctx->ctx.pmu); } /* @@ -2077,55 +2101,31 @@ static void ___perf_install_in_context(void *info) */ static int __perf_install_in_context(void *info) { - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; + struct perf_event_context *ctx = info; struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); struct perf_event_context *task_ctx = cpuctx->task_ctx; - struct task_struct *task = current; - - perf_ctx_lock(cpuctx, task_ctx); - perf_pmu_disable(cpuctx->ctx.pmu); - - /* - * If there was an active task_ctx schedule it out. - */ - if (task_ctx) - task_ctx_sched_out(task_ctx); - /* - * If the context we're installing events in is not the - * active task_ctx, flip them. - */ - if (ctx->task && task_ctx != ctx) { - if (task_ctx) - raw_spin_unlock(&task_ctx->lock); + raw_spin_lock(&cpuctx->ctx.lock); + if (ctx->task) { raw_spin_lock(&ctx->lock); + /* + * If we hit the 'wrong' task, we've since scheduled and + * everything should be sorted, nothing to do! + */ task_ctx = ctx; - } + if (ctx->task != current) + goto unlock; - if (task_ctx) { - cpuctx->task_ctx = task_ctx; - task = task_ctx->task; + /* + * If task_ctx is set, it had better be to us. + */ + WARN_ON_ONCE(cpuctx->task_ctx != ctx && cpuctx->task_ctx); + } else if (task_ctx) { + raw_spin_lock(&task_ctx->lock); } - cpu_ctx_sched_out(cpuctx, EVENT_ALL); - - update_context_time(ctx); - /* - * update cgrp time only if current cgrp - * matches event->cgrp. Must be done before - * calling add_event_to_ctx() - */ - update_cgrp_time_from_event(event); - - add_event_to_ctx(event, ctx); - - /* - * Schedule everything back in - */ - perf_event_sched_in(cpuctx, task_ctx, task); - - perf_pmu_enable(cpuctx->ctx.pmu); + ctx_resched(cpuctx, task_ctx); +unlock: perf_ctx_unlock(cpuctx, task_ctx); return 0; @@ -2133,27 +2133,54 @@ static int __perf_install_in_context(void *info) /* * Attach a performance event to a context - * - * First we add the event to the list with the hardware enable bit - * in event->hw_config cleared. - * - * If the event is attached to a task which is on a CPU we use a smp - * call to enable it in the task context. The task might have been - * scheduled away, but we check this in the smp call again. */ static void perf_install_in_context(struct perf_event_context *ctx, struct perf_event *event, int cpu) { + struct task_struct *task = NULL; + lockdep_assert_held(&ctx->mutex); event->ctx = ctx; if (event->cpu != -1) event->cpu = cpu; - event_function_call(event, __perf_install_in_context, - ___perf_install_in_context, event); + /* + * Installing events is tricky because we cannot rely on ctx->is_active + * to be set in case this is the nr_events 0 -> 1 transition. + * + * So what we do is we add the event to the list here, which will allow + * a future context switch to DTRT and then send a racy IPI. If the IPI + * fails to hit the right task, this means a context switch must have + * happened and that will have taken care of business. + */ + raw_spin_lock_irq(&ctx->lock); + task = ctx->task; + /* + * Worse, we cannot even rely on the ctx actually existing anymore. If + * between find_get_context() and perf_install_in_context() the task + * went through perf_event_exit_task() its dead and we should not be + * adding new events. + */ + if (task == TASK_TOMBSTONE) { + raw_spin_unlock_irq(&ctx->lock); + return; + } + update_context_time(ctx); + /* + * Update cgrp time only if current cgrp matches event->cgrp. + * Must be done before calling add_event_to_ctx(). + */ + update_cgrp_time_from_event(event); + add_event_to_ctx(event, ctx); + raw_spin_unlock_irq(&ctx->lock); + + if (task) + task_function_call(task, __perf_install_in_context, ctx); + else + cpu_function_call(cpu, __perf_install_in_context, ctx); } /* @@ -2180,43 +2207,30 @@ static void __perf_event_mark_enabled(struct perf_event *event) /* * Cross CPU call to enable a performance event */ -static int __perf_event_enable(void *info) +static void __perf_event_enable(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct perf_event *event = info; - struct perf_event_context *ctx = event->ctx; struct perf_event *leader = event->group_leader; - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); - int err; + struct perf_event_context *task_ctx; - /* - * There's a time window between 'ctx->is_active' check - * in perf_event_enable function and this place having: - * - IRQs on - * - ctx->lock unlocked - * - * where the task could be killed and 'ctx' deactivated - * by perf_event_exit_task. - */ - if (!ctx->is_active) - return -EINVAL; + if (event->state >= PERF_EVENT_STATE_INACTIVE || + event->state <= PERF_EVENT_STATE_ERROR) + return; - raw_spin_lock(&ctx->lock); update_context_time(ctx); - - if (event->state >= PERF_EVENT_STATE_INACTIVE) - goto unlock; - - /* - * set current task's cgroup time reference point - */ - perf_cgroup_set_timestamp(current, ctx); - __perf_event_mark_enabled(event); + if (!ctx->is_active) + return; + if (!event_filter_match(event)) { - if (is_cgroup_event(event)) + if (is_cgroup_event(event)) { + perf_cgroup_set_timestamp(current, ctx); // XXX ? perf_cgroup_defer_enabled(event); - goto unlock; + } + return; } /* @@ -2224,41 +2238,13 @@ static int __perf_event_enable(void *info) * then don't put it on unless the group is on. */ if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) - goto unlock; - - if (!group_can_go_on(event, cpuctx, 1)) { - err = -EEXIST; - } else { - if (event == leader) - err = group_sched_in(event, cpuctx, ctx); - else - err = event_sched_in(event, cpuctx, ctx); - } - - if (err) { - /* - * If this event can't go on and it's part of a - * group, then the whole group has to come off. - */ - if (leader != event) { - group_sched_out(leader, cpuctx, ctx); - perf_mux_hrtimer_restart(cpuctx); - } - if (leader->attr.pinned) { - update_group_times(leader); - leader->state = PERF_EVENT_STATE_ERROR; - } - } + return; -unlock: - raw_spin_unlock(&ctx->lock); + task_ctx = cpuctx->task_ctx; + if (ctx->task) + WARN_ON_ONCE(task_ctx != ctx); - return 0; -} - -void ___perf_event_enable(void *info) -{ - __perf_event_mark_enabled((struct perf_event *)info); + ctx_resched(cpuctx, task_ctx); } /* @@ -2275,7 +2261,8 @@ static void _perf_event_enable(struct perf_event *event) struct perf_event_context *ctx = event->ctx; raw_spin_lock_irq(&ctx->lock); - if (event->state >= PERF_EVENT_STATE_INACTIVE) { + if (event->state >= PERF_EVENT_STATE_INACTIVE || + event->state < PERF_EVENT_STATE_ERROR) { raw_spin_unlock_irq(&ctx->lock); return; } @@ -2291,8 +2278,7 @@ static void _perf_event_enable(struct perf_event *event) event->state = PERF_EVENT_STATE_OFF; raw_spin_unlock_irq(&ctx->lock); - event_function_call(event, __perf_event_enable, - ___perf_event_enable, event); + event_function_call(event, __perf_event_enable, NULL); } /* @@ -2342,12 +2328,27 @@ static void ctx_sched_out(struct perf_event_context *ctx, struct perf_cpu_context *cpuctx, enum event_type_t event_type) { - struct perf_event *event; int is_active = ctx->is_active; + struct perf_event *event; - ctx->is_active &= ~event_type; - if (likely(!ctx->nr_events)) + lockdep_assert_held(&ctx->lock); + + if (likely(!ctx->nr_events)) { + /* + * See __perf_remove_from_context(). + */ + WARN_ON_ONCE(ctx->is_active); + if (ctx->task) + WARN_ON_ONCE(cpuctx->task_ctx); return; + } + + ctx->is_active &= ~event_type; + if (ctx->task) { + WARN_ON_ONCE(cpuctx->task_ctx != ctx); + if (!ctx->is_active) + cpuctx->task_ctx = NULL; + } update_context_time(ctx); update_cgrp_time_from_cpuctx(cpuctx); @@ -2518,17 +2519,21 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn, raw_spin_lock(&ctx->lock); raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING); if (context_equiv(ctx, next_ctx)) { - /* - * XXX do we need a memory barrier of sorts - * wrt to rcu_dereference() of perf_event_ctxp - */ - task->perf_event_ctxp[ctxn] = next_ctx; - next->perf_event_ctxp[ctxn] = ctx; - ctx->task = next; - next_ctx->task = task; + WRITE_ONCE(ctx->task, next); + WRITE_ONCE(next_ctx->task, task); swap(ctx->task_ctx_data, next_ctx->task_ctx_data); + /* + * RCU_INIT_POINTER here is safe because we've not + * modified the ctx and the above modification of + * ctx->task and ctx->task_ctx_data are immaterial + * since those values are always verified under + * ctx->lock which we're now holding. + */ + RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], next_ctx); + RCU_INIT_POINTER(next->perf_event_ctxp[ctxn], ctx); + do_switch = 0; perf_event_sync_stat(ctx, next_ctx); @@ -2541,8 +2546,7 @@ unlock: if (do_switch) { raw_spin_lock(&ctx->lock); - ctx_sched_out(ctx, cpuctx, EVENT_ALL); - cpuctx->task_ctx = NULL; + task_ctx_sched_out(cpuctx, ctx); raw_spin_unlock(&ctx->lock); } } @@ -2637,10 +2641,9 @@ void __perf_event_task_sched_out(struct task_struct *task, perf_cgroup_sched_out(task, next); } -static void task_ctx_sched_out(struct perf_event_context *ctx) +static void task_ctx_sched_out(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) { - struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); - if (!cpuctx->task_ctx) return; @@ -2648,7 +2651,6 @@ static void task_ctx_sched_out(struct perf_event_context *ctx) return; ctx_sched_out(ctx, cpuctx, EVENT_ALL); - cpuctx->task_ctx = NULL; } /* @@ -2725,13 +2727,22 @@ ctx_sched_in(struct perf_event_context *ctx, enum event_type_t event_type, struct task_struct *task) { - u64 now; int is_active = ctx->is_active; + u64 now; + + lockdep_assert_held(&ctx->lock); - ctx->is_active |= event_type; if (likely(!ctx->nr_events)) return; + ctx->is_active |= event_type; + if (ctx->task) { + if (!is_active) + cpuctx->task_ctx = ctx; + else + WARN_ON_ONCE(cpuctx->task_ctx != ctx); + } + now = perf_clock(); ctx->timestamp = now; perf_cgroup_set_timestamp(task, ctx); @@ -2773,12 +2784,7 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, * cpu flexible, task flexible. */ cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); - - if (ctx->nr_events) - cpuctx->task_ctx = ctx; - - perf_event_sched_in(cpuctx, cpuctx->task_ctx, task); - + perf_event_sched_in(cpuctx, ctx, task); perf_pmu_enable(ctx->pmu); perf_ctx_unlock(cpuctx, ctx); } @@ -2800,6 +2806,16 @@ void __perf_event_task_sched_in(struct task_struct *prev, struct perf_event_context *ctx; int ctxn; + /* + * If cgroup events exist on this CPU, then we need to check if we have + * to switch in PMU state; cgroup event are system-wide mode only. + * + * Since cgroup events are CPU events, we must schedule these in before + * we schedule in the task events. + */ + if (atomic_read(this_cpu_ptr(&perf_cgroup_events))) + perf_cgroup_sched_in(prev, task); + for_each_task_context_nr(ctxn) { ctx = task->perf_event_ctxp[ctxn]; if (likely(!ctx)) @@ -2807,13 +2823,6 @@ void __perf_event_task_sched_in(struct task_struct *prev, perf_event_context_sched_in(ctx, task); } - /* - * if cgroup events exist on this CPU, then we need - * to check if we have to switch in PMU state. - * cgroup event are system-wide mode only - */ - if (atomic_read(this_cpu_ptr(&perf_cgroup_events))) - perf_cgroup_sched_in(prev, task); if (atomic_read(&nr_switch_events)) perf_event_switch(task, prev, true); @@ -3099,46 +3108,30 @@ static int event_enable_on_exec(struct perf_event *event, static void perf_event_enable_on_exec(int ctxn) { struct perf_event_context *ctx, *clone_ctx = NULL; + struct perf_cpu_context *cpuctx; struct perf_event *event; unsigned long flags; int enabled = 0; - int ret; local_irq_save(flags); ctx = current->perf_event_ctxp[ctxn]; if (!ctx || !ctx->nr_events) goto out; - /* - * We must ctxsw out cgroup events to avoid conflict - * when invoking perf_task_event_sched_in() later on - * in this function. Otherwise we end up trying to - * ctxswin cgroup events which are already scheduled - * in. - */ - perf_cgroup_sched_out(current, NULL); - - raw_spin_lock(&ctx->lock); - task_ctx_sched_out(ctx); - - list_for_each_entry(event, &ctx->event_list, event_entry) { - ret = event_enable_on_exec(event, ctx); - if (ret) - enabled = 1; - } + cpuctx = __get_cpu_context(ctx); + perf_ctx_lock(cpuctx, ctx); + list_for_each_entry(event, &ctx->event_list, event_entry) + enabled |= event_enable_on_exec(event, ctx); /* - * Unclone this context if we enabled any event. + * Unclone and reschedule this context if we enabled any event. */ - if (enabled) + if (enabled) { clone_ctx = unclone_ctx(ctx); + ctx_resched(cpuctx, ctx); + } + perf_ctx_unlock(cpuctx, ctx); - raw_spin_unlock(&ctx->lock); - - /* - * Also calls ctxswin for cgroup events, if any: - */ - perf_event_context_sched_in(ctx, ctx->task); out: local_irq_restore(flags); @@ -3334,7 +3327,6 @@ static void __perf_event_init_context(struct perf_event_context *ctx) INIT_LIST_HEAD(&ctx->flexible_groups); INIT_LIST_HEAD(&ctx->event_list); atomic_set(&ctx->refcount, 1); - INIT_DELAYED_WORK(&ctx->orphans_remove, orphans_remove_work); } static struct perf_event_context * @@ -3521,11 +3513,13 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu) static void unaccount_event(struct perf_event *event) { + bool dec = false; + if (event->parent) return; if (event->attach_state & PERF_ATTACH_TASK) - static_key_slow_dec_deferred(&perf_sched_events); + dec = true; if (event->attr.mmap || event->attr.mmap_data) atomic_dec(&nr_mmap_events); if (event->attr.comm) @@ -3535,12 +3529,15 @@ static void unaccount_event(struct perf_event *event) if (event->attr.freq) atomic_dec(&nr_freq_events); if (event->attr.context_switch) { - static_key_slow_dec_deferred(&perf_sched_events); + dec = true; atomic_dec(&nr_switch_events); } if (is_cgroup_event(event)) - static_key_slow_dec_deferred(&perf_sched_events); + dec = true; if (has_branch_stack(event)) + dec = true; + + if (dec) static_key_slow_dec_deferred(&perf_sched_events); unaccount_event_cpu(event, event->cpu); @@ -3556,7 +3553,7 @@ static void unaccount_event(struct perf_event *event) * 3) two matching events on the same context. * * The former two cases are handled in the allocation path (perf_event_alloc(), - * __free_event()), the latter -- before the first perf_install_in_context(). + * _free_event()), the latter -- before the first perf_install_in_context(). */ static int exclusive_event_init(struct perf_event *event) { @@ -3631,29 +3628,6 @@ static bool exclusive_event_installable(struct perf_event *event, return true; } -static void __free_event(struct perf_event *event) -{ - if (!event->parent) { - if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) - put_callchain_buffers(); - } - - perf_event_free_bpf_prog(event); - - if (event->destroy) - event->destroy(event); - - if (event->ctx) - put_ctx(event->ctx); - - if (event->pmu) { - exclusive_event_destroy(event); - module_put(event->pmu->module); - } - - call_rcu(&event->rcu_head, free_event_rcu); -} - static void _free_event(struct perf_event *event) { irq_work_sync(&event->pending); @@ -3675,7 +3649,25 @@ static void _free_event(struct perf_event *event) if (is_cgroup_event(event)) perf_detach_cgroup(event); - __free_event(event); + if (!event->parent) { + if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) + put_callchain_buffers(); + } + + perf_event_free_bpf_prog(event); + + if (event->destroy) + event->destroy(event); + + if (event->ctx) + put_ctx(event->ctx); + + if (event->pmu) { + exclusive_event_destroy(event); + module_put(event->pmu->module); + } + + call_rcu(&event->rcu_head, free_event_rcu); } /* @@ -3702,14 +3694,13 @@ static void perf_remove_from_owner(struct perf_event *event) struct task_struct *owner; rcu_read_lock(); - owner = ACCESS_ONCE(event->owner); /* - * Matches the smp_wmb() in perf_event_exit_task(). If we observe - * !owner it means the list deletion is complete and we can indeed - * free this event, otherwise we need to serialize on + * Matches the smp_store_release() in perf_event_exit_task(). If we + * observe !owner it means the list deletion is complete and we can + * indeed free this event, otherwise we need to serialize on * owner->perf_event_mutex. */ - smp_read_barrier_depends(); + owner = lockless_dereference(event->owner); if (owner) { /* * Since delayed_put_task_struct() also drops the last @@ -3737,8 +3728,10 @@ static void perf_remove_from_owner(struct perf_event *event) * ensured they're done, and we can proceed with freeing the * event. */ - if (event->owner) + if (event->owner) { list_del_init(&event->owner_entry); + smp_store_release(&event->owner, NULL); + } mutex_unlock(&owner->perf_event_mutex); put_task_struct(owner); } @@ -3746,36 +3739,98 @@ static void perf_remove_from_owner(struct perf_event *event) static void put_event(struct perf_event *event) { - struct perf_event_context *ctx; - if (!atomic_long_dec_and_test(&event->refcount)) return; + _free_event(event); +} + +/* + * Kill an event dead; while event:refcount will preserve the event + * object, it will not preserve its functionality. Once the last 'user' + * gives up the object, we'll destroy the thing. + */ +int perf_event_release_kernel(struct perf_event *event) +{ + struct perf_event_context *ctx; + struct perf_event *child, *tmp; + if (!is_kernel_event(event)) perf_remove_from_owner(event); + ctx = perf_event_ctx_lock(event); + WARN_ON_ONCE(ctx->parent_ctx); + perf_remove_from_context(event, DETACH_GROUP | DETACH_STATE); + perf_event_ctx_unlock(event, ctx); + /* - * There are two ways this annotation is useful: + * At this point we must have event->state == PERF_EVENT_STATE_EXIT, + * either from the above perf_remove_from_context() or through + * perf_event_exit_event(). * - * 1) there is a lock recursion from perf_event_exit_task - * see the comment there. + * Therefore, anybody acquiring event->child_mutex after the below + * loop _must_ also see this, most importantly inherit_event() which + * will avoid placing more children on the list. * - * 2) there is a lock-inversion with mmap_sem through - * perf_read_group(), which takes faults while - * holding ctx->mutex, however this is called after - * the last filedesc died, so there is no possibility - * to trigger the AB-BA case. + * Thus this guarantees that we will in fact observe and kill _ALL_ + * child events. */ - ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING); - WARN_ON_ONCE(ctx->parent_ctx); - perf_remove_from_context(event, true); - perf_event_ctx_unlock(event, ctx); + WARN_ON_ONCE(event->state != PERF_EVENT_STATE_EXIT); - _free_event(event); -} +again: + mutex_lock(&event->child_mutex); + list_for_each_entry(child, &event->child_list, child_list) { -int perf_event_release_kernel(struct perf_event *event) -{ + /* + * Cannot change, child events are not migrated, see the + * comment with perf_event_ctx_lock_nested(). + */ + ctx = lockless_dereference(child->ctx); + /* + * Since child_mutex nests inside ctx::mutex, we must jump + * through hoops. We start by grabbing a reference on the ctx. + * + * Since the event cannot get freed while we hold the + * child_mutex, the context must also exist and have a !0 + * reference count. + */ + get_ctx(ctx); + + /* + * Now that we have a ctx ref, we can drop child_mutex, and + * acquire ctx::mutex without fear of it going away. Then we + * can re-acquire child_mutex. + */ + mutex_unlock(&event->child_mutex); + mutex_lock(&ctx->mutex); + mutex_lock(&event->child_mutex); + + /* + * Now that we hold ctx::mutex and child_mutex, revalidate our + * state, if child is still the first entry, it didn't get freed + * and we can continue doing so. + */ + tmp = list_first_entry_or_null(&event->child_list, + struct perf_event, child_list); + if (tmp == child) { + perf_remove_from_context(child, DETACH_GROUP); + list_del(&child->child_list); + free_event(child); + /* + * This matches the refcount bump in inherit_event(); + * this can't be the last reference. + */ + put_event(event); + } + + mutex_unlock(&event->child_mutex); + mutex_unlock(&ctx->mutex); + put_ctx(ctx); + goto again; + } + mutex_unlock(&event->child_mutex); + + /* Must be the last reference */ put_event(event); return 0; } @@ -3786,46 +3841,10 @@ EXPORT_SYMBOL_GPL(perf_event_release_kernel); */ static int perf_release(struct inode *inode, struct file *file) { - put_event(file->private_data); + perf_event_release_kernel(file->private_data); return 0; } -/* - * Remove all orphanes events from the context. - */ -static void orphans_remove_work(struct work_struct *work) -{ - struct perf_event_context *ctx; - struct perf_event *event, *tmp; - - ctx = container_of(work, struct perf_event_context, - orphans_remove.work); - - mutex_lock(&ctx->mutex); - list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry) { - struct perf_event *parent_event = event->parent; - - if (!is_orphaned_child(event)) - continue; - - perf_remove_from_context(event, true); - - mutex_lock(&parent_event->child_mutex); - list_del_init(&event->child_list); - mutex_unlock(&parent_event->child_mutex); - - free_event(event); - put_event(parent_event); - } - - raw_spin_lock_irq(&ctx->lock); - ctx->orphans_remove_sched = false; - raw_spin_unlock_irq(&ctx->lock); - mutex_unlock(&ctx->mutex); - - put_ctx(ctx); -} - u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) { struct perf_event *child; @@ -4054,7 +4073,7 @@ static void _perf_event_reset(struct perf_event *event) /* * Holding the top-level event's child_mutex means that any * descendant process that has inherited this event will block - * in sync_child_event if it goes to exit, thus satisfying the + * in perf_event_exit_event() if it goes to exit, thus satisfying the * task existence requirements of perf_event_enable/disable. */ static void perf_event_for_each_child(struct perf_event *event, @@ -4086,36 +4105,14 @@ static void perf_event_for_each(struct perf_event *event, perf_event_for_each_child(sibling, func); } -struct period_event { - struct perf_event *event; - u64 value; -}; - -static void ___perf_event_period(void *info) -{ - struct period_event *pe = info; - struct perf_event *event = pe->event; - u64 value = pe->value; - - if (event->attr.freq) { - event->attr.sample_freq = value; - } else { - event->attr.sample_period = value; - event->hw.sample_period = value; - } - - local64_set(&event->hw.period_left, 0); -} - -static int __perf_event_period(void *info) +static void __perf_event_period(struct perf_event *event, + struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx, + void *info) { - struct period_event *pe = info; - struct perf_event *event = pe->event; - struct perf_event_context *ctx = event->ctx; - u64 value = pe->value; + u64 value = *((u64 *)info); bool active; - raw_spin_lock(&ctx->lock); if (event->attr.freq) { event->attr.sample_freq = value; } else { @@ -4135,14 +4132,10 @@ static int __perf_event_period(void *info) event->pmu->start(event, PERF_EF_RELOAD); perf_pmu_enable(ctx->pmu); } - raw_spin_unlock(&ctx->lock); - - return 0; } static int perf_event_period(struct perf_event *event, u64 __user *arg) { - struct period_event pe = { .event = event, }; u64 value; if (!is_sampling_event(event)) @@ -4157,10 +4150,7 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg) if (event->attr.freq && value > sysctl_perf_event_sample_rate) return -EINVAL; - pe.value = value; - - event_function_call(event, __perf_event_period, - ___perf_event_period, &pe); + event_function_call(event, __perf_event_period, &value); return 0; } @@ -4932,7 +4922,7 @@ static void perf_pending_event(struct irq_work *entry) if (event->pending_disable) { event->pending_disable = 0; - __perf_event_disable(event); + perf_event_disable_local(event); } if (event->pending_wakeup) { @@ -7753,11 +7743,13 @@ static void account_event_cpu(struct perf_event *event, int cpu) static void account_event(struct perf_event *event) { + bool inc = false; + if (event->parent) return; if (event->attach_state & PERF_ATTACH_TASK) - static_key_slow_inc(&perf_sched_events.key); + inc = true; if (event->attr.mmap || event->attr.mmap_data) atomic_inc(&nr_mmap_events); if (event->attr.comm) @@ -7770,11 +7762,14 @@ static void account_event(struct perf_event *event) } if (event->attr.context_switch) { atomic_inc(&nr_switch_events); - static_key_slow_inc(&perf_sched_events.key); + inc = true; } if (has_branch_stack(event)) - static_key_slow_inc(&perf_sched_events.key); + inc = true; if (is_cgroup_event(event)) + inc = true; + + if (inc) static_key_slow_inc(&perf_sched_events.key); account_event_cpu(event, event->cpu); @@ -8422,11 +8417,11 @@ SYSCALL_DEFINE5(perf_event_open, * See perf_event_ctx_lock() for comments on the details * of swizzling perf_event::ctx. */ - perf_remove_from_context(group_leader, false); + perf_remove_from_context(group_leader, 0); list_for_each_entry(sibling, &group_leader->sibling_list, group_entry) { - perf_remove_from_context(sibling, false); + perf_remove_from_context(sibling, 0); put_ctx(gctx); } @@ -8479,6 +8474,8 @@ SYSCALL_DEFINE5(perf_event_open, perf_event__header_size(event); perf_event__id_header_size(event); + event->owner = current; + perf_install_in_context(ctx, event, event->cpu); perf_unpin_context(ctx); @@ -8488,8 +8485,6 @@ SYSCALL_DEFINE5(perf_event_open, put_online_cpus(); - event->owner = current; - mutex_lock(¤t->perf_event_mutex); list_add_tail(&event->owner_entry, ¤t->perf_event_list); mutex_unlock(¤t->perf_event_mutex); @@ -8556,7 +8551,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, } /* Mark owner so we could distinguish it from user events. */ - event->owner = EVENT_OWNER_KERNEL; + event->owner = TASK_TOMBSTONE; account_event(event); @@ -8606,7 +8601,7 @@ void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu) mutex_lock_double(&src_ctx->mutex, &dst_ctx->mutex); list_for_each_entry_safe(event, tmp, &src_ctx->event_list, event_entry) { - perf_remove_from_context(event, false); + perf_remove_from_context(event, 0); unaccount_event_cpu(event, src_cpu); put_ctx(src_ctx); list_add(&event->migrate_entry, &events); @@ -8673,33 +8668,15 @@ static void sync_child_event(struct perf_event *child_event, &parent_event->child_total_time_enabled); atomic64_add(child_event->total_time_running, &parent_event->child_total_time_running); - - /* - * Remove this event from the parent's list - */ - WARN_ON_ONCE(parent_event->ctx->parent_ctx); - mutex_lock(&parent_event->child_mutex); - list_del_init(&child_event->child_list); - mutex_unlock(&parent_event->child_mutex); - - /* - * Make sure user/parent get notified, that we just - * lost one event. - */ - perf_event_wakeup(parent_event); - - /* - * Release the parent event, if this was the last - * reference to it. - */ - put_event(parent_event); } static void -__perf_event_exit_task(struct perf_event *child_event, - struct perf_event_context *child_ctx, - struct task_struct *child) +perf_event_exit_event(struct perf_event *child_event, + struct perf_event_context *child_ctx, + struct task_struct *child) { + struct perf_event *parent_event = child_event->parent; + /* * Do not destroy the 'original' grouping; because of the context * switch optimization the original events could've ended up in a @@ -8712,57 +8689,86 @@ __perf_event_exit_task(struct perf_event *child_event, * Do destroy all inherited groups, we don't care about those * and being thorough is better. */ - perf_remove_from_context(child_event, !!child_event->parent); + raw_spin_lock_irq(&child_ctx->lock); + WARN_ON_ONCE(child_ctx->is_active); + + if (parent_event) + perf_group_detach(child_event); + list_del_event(child_event, child_ctx); + child_event->state = PERF_EVENT_STATE_EXIT; /* see perf_event_release_kernel() */ + raw_spin_unlock_irq(&child_ctx->lock); /* - * It can happen that the parent exits first, and has events - * that are still around due to the child reference. These - * events need to be zapped. + * Parent events are governed by their filedesc, retain them. */ - if (child_event->parent) { - sync_child_event(child_event, child); - free_event(child_event); - } else { - child_event->state = PERF_EVENT_STATE_EXIT; + if (!parent_event) { perf_event_wakeup(child_event); + return; } + /* + * Child events can be cleaned up. + */ + + sync_child_event(child_event, child); + + /* + * Remove this event from the parent's list + */ + WARN_ON_ONCE(parent_event->ctx->parent_ctx); + mutex_lock(&parent_event->child_mutex); + list_del_init(&child_event->child_list); + mutex_unlock(&parent_event->child_mutex); + + /* + * Kick perf_poll() for is_event_hup(). + */ + perf_event_wakeup(parent_event); + free_event(child_event); + put_event(parent_event); } static void perf_event_exit_task_context(struct task_struct *child, int ctxn) { - struct perf_event *child_event, *next; struct perf_event_context *child_ctx, *clone_ctx = NULL; - unsigned long flags; + struct perf_event *child_event, *next; + + WARN_ON_ONCE(child != current); - if (likely(!child->perf_event_ctxp[ctxn])) + child_ctx = perf_pin_task_context(child, ctxn); + if (!child_ctx) return; - local_irq_save(flags); /* - * We can't reschedule here because interrupts are disabled, - * and either child is current or it is a task that can't be - * scheduled, so we are now safe from rescheduling changing - * our context. + * In order to reduce the amount of tricky in ctx tear-down, we hold + * ctx::mutex over the entire thing. This serializes against almost + * everything that wants to access the ctx. + * + * The exception is sys_perf_event_open() / + * perf_event_create_kernel_count() which does find_get_context() + * without ctx::mutex (it cannot because of the move_group double mutex + * lock thing). See the comments in perf_install_in_context(). */ - child_ctx = rcu_dereference_raw(child->perf_event_ctxp[ctxn]); + mutex_lock(&child_ctx->mutex); /* - * Take the context lock here so that if find_get_context is - * reading child->perf_event_ctxp, we wait until it has - * incremented the context's refcount before we do put_ctx below. + * In a single ctx::lock section, de-schedule the events and detach the + * context from the task such that we cannot ever get it scheduled back + * in. */ - raw_spin_lock(&child_ctx->lock); - task_ctx_sched_out(child_ctx); - child->perf_event_ctxp[ctxn] = NULL; + raw_spin_lock_irq(&child_ctx->lock); + task_ctx_sched_out(__get_cpu_context(child_ctx), child_ctx); /* - * If this context is a clone; unclone it so it can't get - * swapped to another process while we're removing all - * the events from it. + * Now that the context is inactive, destroy the task <-> ctx relation + * and mark the context dead. */ + RCU_INIT_POINTER(child->perf_event_ctxp[ctxn], NULL); + put_ctx(child_ctx); /* cannot be last */ + WRITE_ONCE(child_ctx->task, TASK_TOMBSTONE); + put_task_struct(current); /* cannot be last */ + clone_ctx = unclone_ctx(child_ctx); - update_context_time(child_ctx); - raw_spin_unlock_irqrestore(&child_ctx->lock, flags); + raw_spin_unlock_irq(&child_ctx->lock); if (clone_ctx) put_ctx(clone_ctx); @@ -8774,20 +8780,8 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) */ perf_event_task(child, child_ctx, 0); - /* - * We can recurse on the same lock type through: - * - * __perf_event_exit_task() - * sync_child_event() - * put_event() - * mutex_lock(&ctx->mutex) - * - * But since its the parent context it won't be the same instance. - */ - mutex_lock(&child_ctx->mutex); - list_for_each_entry_safe(child_event, next, &child_ctx->event_list, event_entry) - __perf_event_exit_task(child_event, child_ctx, child); + perf_event_exit_event(child_event, child_ctx, child); mutex_unlock(&child_ctx->mutex); @@ -8812,8 +8806,7 @@ void perf_event_exit_task(struct task_struct *child) * the owner, closes a race against perf_release() where * we need to serialize on the owner->perf_event_mutex. */ - smp_wmb(); - event->owner = NULL; + smp_store_release(&event->owner, NULL); } mutex_unlock(&child->perf_event_mutex); @@ -8896,21 +8889,20 @@ void perf_event_delayed_put(struct task_struct *task) WARN_ON_ONCE(task->perf_event_ctxp[ctxn]); } -struct perf_event *perf_event_get(unsigned int fd) +struct file *perf_event_get(unsigned int fd) { - int err; - struct fd f; - struct perf_event *event; + struct file *file; - err = perf_fget_light(fd, &f); - if (err) - return ERR_PTR(err); + file = fget_raw(fd); + if (!file) + return ERR_PTR(-EBADF); - event = f.file->private_data; - atomic_long_inc(&event->refcount); - fdput(f); + if (file->f_op != &perf_fops) { + fput(file); + return ERR_PTR(-EBADF); + } - return event; + return file; } const struct perf_event_attr *perf_event_attrs(struct perf_event *event) @@ -8953,8 +8945,16 @@ inherit_event(struct perf_event *parent_event, if (IS_ERR(child_event)) return child_event; + /* + * is_orphaned_event() and list_add_tail(&parent_event->child_list) + * must be under the same lock in order to serialize against + * perf_event_release_kernel(), such that either we must observe + * is_orphaned_event() or they will observe us on the child_list. + */ + mutex_lock(&parent_event->child_mutex); if (is_orphaned_event(parent_event) || !atomic_long_inc_not_zero(&parent_event->refcount)) { + mutex_unlock(&parent_event->child_mutex); free_event(child_event); return NULL; } @@ -9002,8 +9002,6 @@ inherit_event(struct perf_event *parent_event, /* * Link this into the parent event's child list */ - WARN_ON_ONCE(parent_event->ctx->parent_ctx); - mutex_lock(&parent_event->child_mutex); list_add_tail(&child_event->child_list, &parent_event->child_list); mutex_unlock(&parent_event->child_mutex); @@ -9221,13 +9219,14 @@ static void perf_event_init_cpu(int cpu) #if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC_CORE static void __perf_event_exit_context(void *__info) { - struct remove_event re = { .detach_group = true }; struct perf_event_context *ctx = __info; + struct perf_cpu_context *cpuctx = __get_cpu_context(ctx); + struct perf_event *event; - rcu_read_lock(); - list_for_each_entry_rcu(re.event, &ctx->event_list, event_entry) - __perf_remove_from_context(&re); - rcu_read_unlock(); + raw_spin_lock(&ctx->lock); + list_for_each_entry(event, &ctx->event_list, event_entry) + __perf_remove_from_context(event, cpuctx, ctx, (void *)DETACH_GROUP); + raw_spin_unlock(&ctx->lock); } static void perf_event_exit_cpu_context(int cpu) |