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

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Message-ID: <20110326173545.GA22919@redhat.com>
Date:	Sat, 26 Mar 2011 18:35:45 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Jiri Olsa <jolsa@...hat.com>, Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH,RFC] perf: panic due to inclied cpu context task_ctx
	value

On 03/26, Oleg Nesterov wrote:
>
> On 03/26, Peter Zijlstra wrote:
> >
> > diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> > index c75925c..e9e4e35 100644
> > --- a/kernel/perf_event.c
> > +++ b/kernel/perf_event.c
> > @@ -1073,6 +1073,8 @@ event_sched_out(struct perf_event *event,
> >  	if (!is_software_event(event))
> >  		cpuctx->active_oncpu--;
> >  	ctx->nr_active--;
> > +	if (!ctx->nr_active && cpuctx->task_ctx == ctx)
> > +		cpuctx->task_ctx = NULL;
>
> If we clear cpuctx->task_ctx, we should also clear ctx->is_active.
>
> Otherwise I can't see any problem, but I do not understand this code
> enough.

but probably we also need update_context_time().

Oleg.

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