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Subject: Re: [PATCH 2.6.27-rc5 re-resubmit] Fix itimer/many thread hang.
From: Frank Mayhar <fmayhar@google.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel <linux-kernel@vger.kernel.org>,
       Roland McGrath <roland@redhat.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Alexey Dobriyan <adobriyan@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>
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Organization: Google, Inc.
Date: Tue, 23 Sep 2008 15:56:00 -0700
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On Tue, 2008-09-23 at 17:59 +0400, Oleg Nesterov wrote:
> Looks like task_delta_exec() forgets to unlock rq.

Actually it shouldn't be locking rq.  I failed to delete the lock.

> Confused. Unless I misread the patch, tgtimes->totals can be NULL
> on UP too?

Yeah.  I totally messed up on this, too many things going on at once.
I've eliminated the SMP/UP split in sched_stats.h and pulled it all into
the three basic functions.

> (of course, this can't explain the crash)

I'll be investigating this in the morning (I'm at home today and without
a test box).
-- 
Frank Mayhar <fmayhar@google.com>
Google, Inc.