From: Tejun Heo <tj@kernel.org>
Date: Fri, 3 Aug 2012 17:30:45 +0000 (-0700)
Subject: workqueue: add missing smp_wmb() in process_one_work()
X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~52^2~45
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=959d1af8cffc8fd38ed53e8be1cf4ab8782f9c00;p=pandora-kernel.git

workqueue: add missing smp_wmb() in process_one_work()

WORK_STRUCT_PENDING is used to claim ownership of a work item and
process_one_work() releases it before starting execution.  When
someone else grabs PENDING, all pre-release updates to the work item
should be visible and all updates made by the new owner should happen
afterwards.

Grabbing PENDING uses test_and_set_bit() and thus has a full barrier;
however, clearing doesn't have a matching wmb.  Given the preceding
spin_unlock and use of clear_bit, I don't believe this can be a
problem on an actual machine and there hasn't been any related report
but it still is theretically possible for clear_pending to permeate
upwards and happen before work->entry update.

Add an explicit smp_wmb() before work_clear_pending().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
---

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