[PATCH 08/15] perf: optimize perf_event_task_sched_out

[Peter Zijlstra]

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@xxxxxxxxx>
---
 kernel/perf_event.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -1120,6 +1120,8 @@ static void perf_event_sync_stat(struct 
 	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 ta
 	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;

-- 

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