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authorLinus Torvalds <torvalds@linux-foundation.org>2016-04-27 12:03:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-04-27 12:03:59 -0700
commitb75a2bf899b668b1d52de8846aafdbcf81349c73 (patch)
tree6696988bd5a31543833d4b275605d766e0a20840 /kernel/kexec_core.c
parent763cfc86ee8fd728a7cf2334b8d3a897af7a7ade (diff)
parent346c09f80459a3ad97df1816d6d606169a51001a (diff)
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Merge branch 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue fix from Tejun Heo: "So, it turns out we had a silly bug in the most fundamental part of workqueue for a very long time. AFAICS, this dates back to pre-git era and has quite likely been there from the time workqueue was first introduced. A work item uses its PENDING bit to synchronize multiple queuers. Anyone who wins the PENDING bit owns the pending state of the work item. Whether a queuer wins or loses the race, one thing should be guaranteed - there will soon be at least one execution of the work item - where "after" means that the execution instance would be able to see all the changes that the queuer has made prior to the queueing attempt. Unfortunately, we were missing a smp_mb() after clearing PENDING for execution, so nothing guaranteed visibility of the changes that a queueing loser has made, which manifested as a reproducible blk-mq stall. Lots of kudos to Roman for debugging the problem. The patch for -stable is the minimal one. For v3.7, Peter is working on a patch to make the code path slightly more efficient and less fragile" * 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: workqueue: fix ghost PENDING flag while doing MQ IO
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