From: Tejun Heo Date: Fri, 3 Aug 2012 17:30:45 +0000 (-0700) Subject: workqueue: add missing smp_wmb() in process_one_work() X-Git-Tag: v3.2.32~143 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=563ce0476bddbd8e9818c3c7088186dd01479ffe;p=pandora-kernel.git workqueue: add missing smp_wmb() in process_one_work() commit 959d1af8cffc8fd38ed53e8be1cf4ab8782f9c00 upstream. 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 Cc: Oleg Nesterov Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed