#include <asm/irq_regs.h>
-static struct workqueue_struct *perf_wq;
-
typedef int (*remote_function_f)(void *);
struct remote_function_call {
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 task_struct *task = ctx->task;
+ 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 = 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 |\
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
* 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
* 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);
/*
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);
}
* 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()
* 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
*/
/*
* 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.
*/
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();
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;
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;
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;
if (event->attr.exclusive || !cpuctx->active_oncpu)
cpuctx->exclusive = 0;
- if (is_orphaned_child(event))
- schedule_orphans_remove(ctx);
-
perf_pmu_enable(event->pmu);
}
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
* 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
* 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;
}
/*
* 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.
}
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);
}
/*
if (event->attr.exclusive)
cpuctx->exclusive = 1;
- if (is_orphaned_child(event))
- schedule_orphans_remove(ctx);
-
out:
perf_pmu_enable(event->pmu);
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,
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);
}
/*
*/
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;
/*
* 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);
}
/*
/*
* 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;
}
/*
* 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;
- }
- }
-
-unlock:
- raw_spin_unlock(&ctx->lock);
+ return;
- return 0;
-}
+ task_ctx = cpuctx->task_ctx;
+ if (ctx->task)
+ WARN_ON_ONCE(task_ctx != ctx);
-void ___perf_event_enable(void *info)
-{
- __perf_event_mark_enabled((struct perf_event *)info);
+ ctx_resched(cpuctx, task_ctx);
}
/*
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;
}
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);
}
/*
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);
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);
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);
}
}
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;
return;
ctx_sched_out(ctx, cpuctx, EVENT_ALL);
- cpuctx->task_ctx = NULL;
}
/*
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);
* 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);
}
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))
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);
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);
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 *
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)
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);
* 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)
{
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);
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);
}
/*
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
* 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);
}
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;
}
*/
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;
/*
* 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,
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 {
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))
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;
}
struct perf_event *event = filp->private_data;
int retval;
- mutex_lock(&inode->i_mutex);
+ inode_lock(inode);
retval = fasync_helper(fd, filp, on, &event->fasync);
- mutex_unlock(&inode->i_mutex);
+ inode_unlock(inode);
if (retval < 0)
return retval;
if (event->pending_disable) {
event->pending_disable = 0;
- __perf_event_disable(event);
+ perf_event_disable_local(event);
}
if (event->pending_wakeup) {
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)
}
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);
* 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);
}
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);
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);
}
/* Mark owner so we could distinguish it from user events. */
- event->owner = EVENT_OWNER_KERNEL;
+ event->owner = TASK_TOMBSTONE;
account_event(event);
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);
&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
* 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);
*/
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);
* 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);
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)
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;
}
/*
* 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);
#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)
projects / cascardo / linux.git / blobdiff