linux-kernel - Re: Hard lockup with timer events

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Date:	Wed, 11 Nov 2009 14:23:01 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Soeren Sandmann <sandmann@...mi.au.dk>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...utronix.de,
	acme@...hat.com, rosted@...dmis.org, paulus@...ba.org
Subject: Re: Hard lockup with timer events

On Wed, 2009-11-11 at 05:50 +0100, Frederic Weisbecker wrote:
> On Thu, Oct 29, 2009 at 08:15:03PM +0100, Soeren Sandmann wrote:
> > Hi,
> > 
> > This program
> > 
> >         http://www.daimi.au.dk/~sandmann/lockup.c
> > 
> > locks up hard for me on a Pentium 4 in 32 bit mode, with the hrtimer
> > patches applied (-tip for example).
> > 
> > What the program does is spawn a thread that just spins, and then 400
> > threads that each create a performance counter of type
> > PERF_COUNT_SW_CPU_CLOCK and a sample period of 1000000 and a
> > sample_type of
> > 
> >         PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_CALLCHAIN
> > 
> > These threads then map the event buffer and read it continuously.
> > 
> > It does not apparently lock up if SAMPLE_CALLCHAIN is removed; also I
> > cannot get it to lock up on Core 2 Duo in either 32 or 64 bit mode.
> > 
> > 
> > Soren
> 
> 
> 
> It locks up hard for me too, no more blinking cursor, nothing.
> I've attached my config, it's against tip:master from yesterday.

What kind of cpu does your laptop have? The .config seems to suggest a
Core2. Which would make Soeren's report of not being able to trash a
64bit core2 'interesting' ;-)
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