linux-kernel - Re: Failure to release lock after CPU hot-unplug canceled

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Message-ID: <45A3C420.8010708@cs.cmu.edu>
Date:	Tue, 09 Jan 2007 11:34:40 -0500
From:	Benjamin Gilbert <bgilbert@...cmu.edu>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
CC:	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Gautham shenoy <ego@...ibm.com>, Andrew Morton <akpm@...l.org>
Subject: Re: Failure to release lock after CPU hot-unplug canceled

Heiko Carstens wrote:
> On Tue, Jan 09, 2007 at 05:57:40PM +0530, Srivatsa Vaddagiri wrote:
>> On Tue, Jan 09, 2007 at 01:17:38PM +0100, Heiko Carstens wrote:
>>> The workqueue code grabs a lock on CPU_[UP|DOWN]_PREPARE and releases it
>>> again on CPU_DOWN_FAILED/CPU_UP_CANCELED. If something in the callchain
>>> returns NOTIFY_BAD the rest of the entries in the callchain won't be
>>> called anymore. But DOWN_FAILED/UP_CANCELED will be called for every
>>> entry.
>>> So we might even end up with a mutex_unlock(&workqueue_mutex) even if
>>> mutex_lock(&workqueue_mutex) hasn't been called...
 >>
>> This is a known problem. Gautham had sent out patches to address them
>>
>> http://lkml.org/lkml/2006/11/14/93
>>
>> Looks like they are in latest mm tree. Perhaps the testcase should be
>> retried against latest mm.
 >
> Ah, nice! Wasn't aware of that. But I still think we should have a
> CPU_DOWN_FAILED in case CPU_DOWN_PREPARED failed.
> Also the slab cache code hasn't been changed to make use of the of the
> new CPU_LOCK_[ACQUIRE|RELEASE] stuff. I'm going to send patches in reply
> to this mail.

2.6.20-rc3-mm1 plus your patches fixes it for me.

Thanks
--Benjamin Gilbert

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