linux-kernel - Re: WARNING in arch/x86/kernel/cpu/perf

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Message-ID: <20130523152657.GF23650@twins.programming.kicks-ass.net>
Date:	Thu, 23 May 2013 17:26:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	trinity@...r.kernel.org
Subject: Re: WARNING in arch/x86/kernel/cpu/perf_event.c

On Thu, May 23, 2013 at 10:29:07AM -0400, Vince Weaver wrote:
> Hello,
> 
> so now that I got past the OOPS in perf_mmap_close() I re-ran
> the fuzzer and quickly encountered the following WARNing.
> 
> It happens here:
> 
> static void x86_pmu_start(struct perf_event *event, int flags)
> {
>         struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
>         int idx = event->hw.idx;
> 
>         if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
>                 return;
> 
> 
> Is it worth trying to come up with a reproducible case for this one?
> 
> I never know how seriously to take WARN_ON_ONCE dumps.

Its not supposed to happen, you're trying to start an already running
event. I'll put it on the todo list.
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