linux-kernel - Re: x86_pmu_start WARN

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Message-ID: <alpine.DEB.2.10.1402181717300.20073@vincent-weaver-1.um.maine.edu>
Date:	Tue, 18 Feb 2014 17:20:57 -0500 (EST)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Vince Weaver <vincent.weaver@...ne.edu>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: x86_pmu_start WARN_ON.

On Tue, 18 Feb 2014, Vince Weaver wrote:

> On Mon, 17 Feb 2014, Peter Zijlstra wrote:
> 
> > Enable CONFIG_FRAME_POINTER for better stack traces; I suspect the
> > list_del_event() is just random stack garbage. The path that makes sense
> > is:
> >   wait_rcu()->__wait_for_common()->schedule_timeout()
> 
> Here's an updated stack trace on 3.14-rc3 with CONFIG_FRAME_POINTER 
> enabled, in case it's helpful:

Still chasing this, although all I can add are these debug messages:

[  140.812003] PROBLEM: n_events=2 n_added=2 VMW: idx=33 state=f00 type=0 config=0 samp_per=5e6069eb0
[  140.812003] ALL: VMW: Num=0 idx=33 state=f00 type=0 config=0 samp_per=5e6069eb0
[  140.812003] ALL: VMW: Num=1 idx=0 state=3 type=0 config=1 samp_per=0

So when the WARN gets triggered there only only two events in the event
list, the NMI watchdog which has already been enabled somehow (that f00
I stuck in, pmu_start sets it to f00 instead of 00 to make sure it wasn't
something stomping on memory) and the precise instructions event.

I still have a hard time following what all the schedule in code is doing.

Vince
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