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    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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