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

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