From: Thomas Tuttle <ttuttle@chromium.org>
Date: Wed, 14 Sep 2011 23:22:28 +0000 (-0700)
Subject: workqueue: lock cwq access in drain_workqueue
X-Git-Tag: v3.1-rc7~38
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa2563e41c3d6d6e8af437643981ed28ae0cb56d;p=pandora-kernel.git

workqueue: lock cwq access in drain_workqueue

Take cwq->gcwq->lock to avoid racing between drain_workqueue checking to
make sure the workqueues are empty and cwq_dec_nr_in_flight decrementing
and then incrementing nr_active when it activates a delayed work.

We discovered this when a corner case in one of our drivers resulted in
us trying to destroy a workqueue in which the remaining work would
always requeue itself again in the same workqueue.  We would hit this
race condition and trip the BUG_ON on workqueue.c:3080.

Signed-off-by: Thomas Tuttle <ttuttle@chromium.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

Reading git-diff-tree failed