linux-kernel - Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

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Date:	Tue, 24 Apr 2007 13:24:24 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Rick Lindsley <ricklind@...ibm.com>,
	john stultz <johnstul@...ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	virtualization@...ts.osdl.org,
	Chris Lalancette <clalance@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
>   
>> Well, it _is_ mysterious.
>>
>> Did you try to locate the code which failed?  I got lost in macros and
>> include files, and gave up very very easily.  Stop hiding, Ingo.
>>   
>>     
>
> OK, I've managed to reproduce it.  Removing the local_irq_save/restore
> from sched_clock() makes it go away, as I'd expect (otherwise it would
> really be magic).  But given that it never seems to touch the softlockup
> during testing, I have no idea what difference it makes...

And sched_clock's use of local_irq_save/restore appears to be absolutely
correct, so I think it must be triggering a bug in either the self-tests
or lockdep itself.

The only way I could actually extract the test code itself was to run
the whole thing through cpp+indent, but it doesn't shed much light.

It's also not clear to me if there are 6 independent failures, or if
they're a cascade.

    J
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