linux-kernel - Hard lockup with timer events

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Date:	29 Oct 2009 20:15:03 +0100
From:	Soeren Sandmann <sandmann@...mi.au.dk>
To:	linux-kernel@...r.kernel.org, mingo@...e.hu
Cc:	a.p.zijlstra@...llo.nl, fweisbec@...il.com, tglx@...utronix.de,
	acme@...hat.com, rosted@...dmis.org, paulus@...ba.org
Subject: Hard lockup with timer events

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
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