From: Tejun Heo <tj@kernel.org>
Date: Tue, 12 Mar 2013 18:30:04 +0000 (-0700)
Subject: workqueue: implement apply_workqueue_attrs()
X-Git-Tag: omap-for-v3.10/dt-fixes-for-merge-window~125^2~55
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9e8cd2f5898ab6710ad81f4583fada08bf8049a4;p=pandora-kernel.git

workqueue: implement apply_workqueue_attrs()

Implement apply_workqueue_attrs() which applies workqueue_attrs to the
specified unbound workqueue by creating a new pwq (pool_workqueue)
linked to worker_pool with the specified attributes.

A new pwq is linked at the head of wq->pwqs instead of tail and
__queue_work() verifies that the first unbound pwq has positive refcnt
before choosing it for the actual queueing.  This is to cover the case
where creation of a new pwq races with queueing.  As base ref on a pwq
won't be dropped without making another pwq the first one,
__queue_work() is guaranteed to make progress and not add work item to
a dead pwq.

init_and_link_pwq() is updated to return the last first pwq the new
pwq replaced, which is put by apply_workqueue_attrs().

Note that apply_workqueue_attrs() is almost identical to unbound pwq
part of alloc_and_link_pwqs().  The only difference is that there is
no previous first pwq.  apply_workqueue_attrs() is implemented to
handle such cases and replaces unbound pwq handling in
alloc_and_link_pwqs().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
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