1. 28 Apr, 2016 39 commits
  2. 27 Apr, 2016 1 commit
    • Linus Torvalds's avatar
      Merge branch 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq · b75a2bf8
      Linus Torvalds authored
      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
      b75a2bf8