[tip:perf/core] perf_events: Fix __perf_event_exit_task() vs. update_event_times() locking

tip-bot for Peter Zijlstra
2009-11-23T11:57:24Z

Commit-ID: f67218c3e93abaf0f480bb94b53d234853ffe4de
Gitweb: http://git.kernel.org/tip/f67218c3e93abaf0f480bb94b53d234853ffe4de
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 23 Nov 2009 11:37:27 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 23 Nov 2009 11:49:57 +0100

perf_events: Fix __perf_event_exit_task() vs. update_event_times() locking

Move the update_event_times() call in __perf_event_exit_task()
into list_del_event() because that holds the proper lock
(ctx->lock) and seems a more natural place to do the last time
update.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091123103819.842455480@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/perf_event.c | 78 +++++++++++++++++++++++++-------------------------
1 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 8be2574..50f11b5 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -246,6 +246,44 @@ static void perf_unpin_context(struct perf_event_context *ctx)
put_ctx(ctx);
}

+static inline u64 perf_clock(void)
+{
+ return cpu_clock(smp_processor_id());
+}
+
+/*
+ * Update the record of the current time in a context.
+ */
+static void update_context_time(struct perf_event_context *ctx)
+{
+ u64 now = perf_clock();
+
+ ctx->time += now - ctx->timestamp;
+ ctx->timestamp = now;
+}
+
+/*
+ * Update the total_time_enabled and total_time_running fields for a event.
+ */
+static void update_event_times(struct perf_event *event)
+{
+ struct perf_event_context *ctx = event->ctx;
+ u64 run_end;
+
+ if (event->state < PERF_EVENT_STATE_INACTIVE ||
+ event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
+ return;
+
+ event->total_time_enabled = ctx->time - event->tstamp_enabled;
+
+ if (event->state == PERF_EVENT_STATE_INACTIVE)
+ run_end = event->tstamp_stopped;
+ else
+ run_end = ctx->time;
+
+ event->total_time_running = run_end - event->tstamp_running;
+}
+
/*
* Add a event from the lists for its context.
* Must be called with ctx->mutex and ctx->lock held.
@@ -294,6 +332,7 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
if (event->group_leader != event)
event->group_leader->nr_siblings--;

+ update_event_times(event);
event->state = PERF_EVENT_STATE_OFF;

/*
@@ -454,44 +493,6 @@ retry:
spin_unlock_irq(&ctx->lock);
}

-static inline u64 perf_clock(void)
-{
- return cpu_clock(smp_processor_id());
-}
-
-/*
- * Update the record of the current time in a context.
- */
-static void update_context_time(struct perf_event_context *ctx)
-{
- u64 now = perf_clock();
-
- ctx->time += now - ctx->timestamp;
- ctx->timestamp = now;
-}
-
-/*
- * Update the total_time_enabled and total_time_running fields for a event.
- */
-static void update_event_times(struct perf_event *event)
-{
- struct perf_event_context *ctx = event->ctx;
- u64 run_end;
-
- if (event->state < PERF_EVENT_STATE_INACTIVE ||
- event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
- return;
-
- event->total_time_enabled = ctx->time - event->tstamp_enabled;
-
- if (event->state == PERF_EVENT_STATE_INACTIVE)
- run_end = event->tstamp_stopped;
- else
- run_end = ctx->time;
-
- event->total_time_running = run_end - event->tstamp_running;
-}
-
/*
* Update total_time_enabled and total_time_running for all events in a group.
*/
@@ -4931,7 +4932,6 @@ __perf_event_exit_task(struct perf_event *child_event,
{
struct perf_event *parent_event;

- update_event_times(child_event);
perf_event_remove_from_context(child_event);

parent_event = child_event->parent;