From: Tejun Heo <tj@kernel.org>
Date: Mon, 9 Mar 2015 13:22:28 +0000 (-0400)
Subject: workqueue: make the workqueues list RCU walkable
X-Git-Tag: omap-for-v4.1/fixes-rc1~170^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e2dca7adff8f3fae0ab250a6362798550b3c79ee;p=pandora-kernel.git

workqueue: make the workqueues list RCU walkable

The workqueues list is protected by wq_pool_mutex and a workqueue and
its subordinate data structures are freed directly on destruction.  We
want to add the ability dump workqueues from a sysrq callback which
requires walking all workqueues without grabbing wq_pool_mutex.  This
patch makes freeing of workqueues RCU protected and makes the
workqueues list walkable while holding RCU read lock.

Note that pool_workqueues and pools are already sched-RCU protected.
For consistency, workqueues are also protected with sched-RCU.

While at it, reverse the workqueues list so that a workqueue which is
created earlier comes before.  The order of the list isn't significant
functionally but this makes the planned sysrq dump list system
workqueues first.

Signed-off-by: Tejun Heo <tj@kernel.org>
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