linux-kernel - Re: Yet more softlockups.

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Message-ID: <alpine.DEB.2.02.1307122136540.2540@pianoman.cluster.toy>
Date:	Fri, 12 Jul 2013 21:40:19 -0400 (EDT)
From:	Vince Weaver <vince@...ter.net>
To:	Dave Jones <davej@...hat.com>
cc:	Dave Hansen <dave.hansen@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Peter Anvin <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: Yet more softlockups.

On Fri, 12 Jul 2013, Dave Jones wrote:

> 
> Here's a fun trick:
> 
> trinity -c perf_event_open -C4 -q -l off
> 
> Within about a minute, that brings any of my boxes to its knees.
> The softlockup detector starts going nuts, and then the box wedges solid.

are you running with the patch

 [PATCH 1/2] perf: Clone child context from parent context pmu

 https://lkml.org/lkml/2013/7/9/310

It hasn't hit Linus git yet.

It fixes a bug that my perf_fuzzer would hit within seconds but it took me 
over a month of trace bisecting and kernel bisecting to isolate it.

The symptoms were stuck processes and NMI tracebacks leading to hard 
locks.  

With the patch applied my perf_fuzzer (which uses the same perf_event_open 
syscall generator as trinity) runs for hours w/o problems.

Vince
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