On Tue, Jun 24, 2014 at 12:39:36PM +0200, Peter Zijlstra wrote:
> 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!
should I queue it with your ack?
jirka
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