perf: Clean up sync_child_event()
sync_child_event() has outgrown its purpose, it does far too much.
Bring it back to its named purpose.
Rename __perf_event_exit_task() to perf_event_exit_event() to better
reflect what it does and move the event->state assignment under the
ctx->lock, like state changes ought to be.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5f055de..8c3d951 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1041,9 +1041,8 @@
* 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()
@@ -1846,7 +1845,8 @@
* 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.
@@ -4086,7 +4086,7 @@
/*
* 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,
@@ -8681,33 +8681,15 @@
&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
@@ -8723,23 +8705,39 @@
raw_spin_lock_irq(&child_ctx->lock);
WARN_ON_ONCE(child_ctx->is_active);
- if (!!child_event->parent)
+ if (parent_event)
perf_group_detach(child_event);
list_del_event(child_event, child_ctx);
+ child_event->state = PERF_EVENT_STATE_EXIT;
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)
@@ -8765,10 +8763,9 @@
*
* We can recurse on the same lock type through:
*
- * __perf_event_exit_task()
- * sync_child_event()
- * put_event()
- * mutex_lock(&ctx->mutex)
+ * perf_event_exit_event()
+ * put_event()
+ * mutex_lock(&ctx->mutex)
*
* But since its the parent context it won't be the same instance.
*/
@@ -8805,7 +8802,7 @@
perf_event_task(child, child_ctx, 0);
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);