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DateSat, 21 Nov 2009 13:43:32 GMT
Fromtip-bot for Peter Zijlstra <>
Subject[tip:perf/core] perf: Fix time locking
Commit-ID:  2b8988c9f7defe319cffe0cd362a7cd356c86f62
Gitweb: http://git.kernel.org/tip/2b8988c9f7defe319cffe0cd362a7cd356c86f62
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 20 Nov 2009 22:19:54 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 21 Nov 2009 14:11:39 +0100

perf: Fix time locking

Most sites updating ctx->time and event times do so under
ctx->lock, make sure they all do.

This was made possible by removing the __perf_event_read() call
from __perf_event_sync_stat(), which already had this lock
taken.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212509.102316434@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/perf_event.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 028619d..fdfae88 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1526,8 +1526,11 @@ static void __perf_event_read(void *info)
if (ctx->task && cpuctx->task_ctx != ctx)
return;

+ spin_lock(&ctx->lock);
update_context_time(ctx);
update_event_times(event);
+ spin_unlock(&ctx->lock);
+
event->pmu->read(event);
}

@@ -1541,7 +1544,13 @@ static u64 perf_event_read(struct perf_event *event)
smp_call_function_single(event->oncpu,
__perf_event_read, event, 1);
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
+ struct perf_event_context *ctx = event->ctx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+ update_context_time(ctx);
update_event_times(event);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}

return atomic64_read(&event->count);

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