linux-kernel - Re: [GIT PULL] perf fixes

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Date:	Fri, 15 Mar 2013 00:11:55 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] perf fixes

On Thu, Mar 14, 2013 at 11:53 PM, Stephane Eranian <eranian@...gle.com> wrote:
> On Thu, Mar 14, 2013 at 11:42 PM, Stephane Eranian <eranian@...gle.com> wrote:
>> On Thu, Mar 14, 2013 at 11:19 PM, Stephane Eranian <eranian@...gle.com> wrote:
>>> On Thu, Mar 14, 2013 at 11:17 PM, Linus Torvalds
>>> <torvalds@...ux-foundation.org> wrote:
>>>> On Thu, Mar 14, 2013 at 3:09 PM, Stephane Eranian <eranian@...gle.com> wrote:
>>>>>
>>>>> Could be related to suspend/resume. But were you running perf across
>>>>> that resume/suspend cycle?
>>>>
>>>> No.
>>>>
>>>> In most cases I was running a perf record before and after (but not
>>>> *while* suspending)
>>>>
>>>> In at least one other crash, I didn't run perf before at all, so the
>>>> first time I used perf was after the resume.
>>>>
>>>> So in no cases did I actually have any perf stuff active over the
>>>> suspend itself.
>>>>
>>> Ok, simpler test case then.
>>>
>>>>> Let's see if we can reproduce the problem on the same ChromeBook you
>>>>> have. Don't have one myself.
>>>>
>>>> I don't imagine it should be about chromebook per se, because afaik
>>>> all of pmu suspend/resume is done by the kernel, no firmware involved.
>>>>
>>>> So I'd assume it should happen with any IvyBridge.
>>>>
>>> Will try on a desktop IvyBridge too.
>>
>> Ok, it happens on my IVB desktop too, so I can investigate...
>
> It's not specific to IVB either, it hangs on my Nehalem desktop as well.

Looks related to PEBS. If I drop the :pp the machine does not hang. Even
a single :p hangs it. So it is possible something is not properly
restored in the
DS state after a resume or is corrupted by the suspend.
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