perf: Optimize perf_event_task_sched_out

Remove an update_context_time() call from the
perf_event_task_sched_out() path and into the branch its needed.

The call was both superfluous, because __perf_event_sched_out()
already does it, and wrong, because it was done without holding
ctx->lock.

Place it in perf_event_sync_stat(), which is the only place it
is needed and which does already hold ctx->lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212508.779516394@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 9a18ff28ea5b..65f4dab0ce60 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1120,6 +1120,8 @@ static void perf_event_sync_stat(struct perf_event_context *ctx,
         if (!ctx->nr_stat)
                 return;
 
+        update_context_time(ctx);
+
         event = list_first_entry(&ctx->event_list,
                                    struct perf_event, event_entry);
 
@@ -1163,8 +1165,6 @@ void perf_event_task_sched_out(struct task_struct *task,
         if (likely(!ctx || !cpuctx->task_ctx))
                 return;
 
-        update_context_time(ctx);
-
         rcu_read_lock();
         parent = rcu_dereference(ctx->parent_ctx);
         next_ctx = next->perf_event_ctxp;