From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Tue, 19 May 2015 10:03:48 +0000 (+0800)
Subject: workqueue: ensure attrs changes are properly synchronized
X-Git-Tag: omap-for-v4.2/fixes-rc1^2~86^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d4d3e2579756e3a5f4fbf8eac211f0696e253bcd;p=pandora-kernel.git

workqueue: ensure attrs changes are properly synchronized

Current modification to attrs via sysfs is not fully synchronized.

Process A (change cpumask)      | Process B (change numa affinity)
wq_cpumask_store()              |
  wq_sysfs_prep_attrs()         |
                                | apply_workqueue_attrs()
  apply_workqueue_attrs()       |

It results that the Process B's operation is totally reverted
without any notification, it is a buggy behavior.  So this patch
moves wq_sysfs_prep_attrs() into the protection under wq_pool_mutex
to ensure attrs changes are properly synchronized.

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