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Date: Fri, 10 Feb 2012 07:10:46 +0100
From: Ingo Molnar <mingo@elte.hu>
To: David Ahern <dsahern@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        x86@kernel.org
Subject: Re: Hmm.. WARN_ON_ONCE(cpuc->enabled)
Message-ID: <20120210061046.GA21805@elte.hu>
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* David Ahern <dsahern@gmail.com> wrote:

> On 02/09/2012 04:46 PM, Linus Torvalds wrote:
> > Ok, so I get the appended on my Core i5 when I did a "perf record -f
> > -e cycles:pp make -j" on the kernel build.
> > 
> > What's up, guys? I haven't tried that particular perf run in a while,
> > so it might have been going on for quite some time.
> 
> Perhaps already fixed by
> https://lkml.org/lkml/2012/2/4/42
> 
> It's not in your tree; but in tip/urgent.

That patch only fixed the symptom - there was an underlying bug 
that is fixed in perf/urgent as well, via:

  f39d47ff819e: perf: Fix double start/stop in x86_pmu_start()

I committed it two days ago - so it narrowly missed -rc3. Note 
that no actual misbehavior is known to be caused by this bug, 
beyond the annoying WARN_ONCE() messages and a potential slight 
mis-measurement.

I'll send those fixes to Linus in a couple of hours.

Thanks,

	Ingo