On Tue, Jun 24, 2014 at 10:20:25AM +0200, Jiri Olsa wrote:
> From: Jiri Olsa <jo...@redhat.com>
>
> The context check in perf_event_context_sched_out allows
> non-cloned context to be part of the optimized schedule
> out switch.
>
> This could move non-cloned context into another workload
> child. Once this child exits, the context is closed and
> leaves all original (parent) events in closed state.
>
> Any other new cloned event will have closed state and not
> measure anything. And probably causing other odd bugs.
>
> Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
> Cc: Corey Ashford <cjash...@linux.vnet.ibm.com>
> Cc: David Ahern <dsah...@gmail.com>
> Cc: Frederic Weisbecker <fweis...@gmail.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Namhyung Kim <namhy...@kernel.org>
> Cc: Paul Mackerras <pau...@samba.org>
> Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
> Signed-off-by: Jiri Olsa <jo...@kernel.org>
> ---
> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index d968008..4e3618e 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -2319,7 +2319,7 @@ static void perf_event_context_sched_out(struct
> task_struct *task, int ctxn,
> next_parent = rcu_dereference(next_ctx->parent_ctx);
>
> /* If neither context have a parent context; they cannot be clones. */
> - if (!parent && !next_parent)
> + if (!parent || !next_parent)
> goto unlock;
>
> if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
Ohh, nice, good catch!
Thanks
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