On Thu, 2009-11-26 at 09:24 -0800, Stephane Eranian wrote:
> When a pinned group cannot be scheduled it goes into error state.
> Normally a group cannot go out of error state without being explicitly
> re-enabled or disabled. There was a bug in per-thread mode, whereby
> upon termination of the thread, the group would transition from error
> to off leading to bogus counts and timing information returned by
> read().
> Signed-off-by: Stephane Eranian <eran...@google.com>
Right, good catch, totally forgot about error state :/
Acked-by: Peter Zijlstra <a.p.zijls...@chello.nl>
> ---
> perf_event.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index 0b0d5f7..7a8bb5b 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -333,7 +333,16 @@ list_del_event(struct perf_event *event, struct
> perf_event_context *ctx)
> event->group_leader->nr_siblings--;
>
> update_event_times(event);
> - event->state = PERF_EVENT_STATE_OFF;
> +
> + /*
> + * If event was in error state, then keep it
> + * that way, otherwise bogus counts will be
> + * returned on read(). The only way to get out
> + * of error state is by explicit re-enabling
> + * of the event
> + */
> + if (event->state > PERF_EVENT_STATE_OFF)
> + event->state = PERF_EVENT_STATE_OFF;
>
> /*
> * If this was a group event with sibling events then
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