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

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Date:	Fri, 15 Mar 2013 01:24:00 +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

Linus,

I bet if you force the affinity of your perf record to be on
a CPU other than CPU0, you will not get the crash.

This is what I am seeing now. I appears on resume,
CPU0 hotplug callbacks for perf_events are not invoked
leaving DS_AREA MSR to 0.

Can you confirm on your machine?



On Fri, Mar 15, 2013 at 12:11 AM, Stephane Eranian <eranian@...gle.com> wrote:
> 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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