linux-kernel - Re: [PATCH,RFC] perf: panic due to inclied cpu context task

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Date:	Wed, 30 Mar 2011 23:26:45 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH,RFC] perf: panic due to inclied cpu context task_ctx
 value

On Wed, 2011-03-30 at 18:37 +0200, Oleg Nesterov wrote:
> > +static void perf_sched_events_dec(void)
> > +{
> > +     jump_label_dec(&perf_sched_events_in);
> > +     JUMP_LABEL(&perf_sched_events_in, no_sync);
> > +     synchronize_sched();
> > +no_sync:
> > +     jump_label_dec(&perf_sched_events_out);
> > +}
> 
> Nice! I didn't realize we can simply use JUMP_LABEL() directly and then
> the code doesn't depend on HAVE_JUMP_LABEL. 

Yeah, avoids having to sprinkle tons of #ifdef goo around ;-)

Anyway how about we do the partial revert below that should get us back
to a working kernel and is a nice small patch to send -stable wards.

After that we can try and be clever with clearing ->task_ctx from things
like remove_from_context and the like.


---
 include/linux/perf_event.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 311b4dc..04d75a8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1086,7 +1086,7 @@ void perf_event_task_sched_out(struct task_struct *task, struct task_struct *nex
 {
 	perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, NULL, 0);
 
-	COND_STMT(&perf_sched_events, __perf_event_task_sched_out(task, next));
+	__perf_event_task_sched_out(task, next);
 }
 
 extern void perf_event_mmap(struct vm_area_struct *vma);

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