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Merge branch 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

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Pull workqueue fix from Tejun Heo:
 "This contains one fix which could lead to system-wide lockup on
  !PREEMPT kernels.  It's very late in the cycle but this definitely is
  a -stable material.

  The problem is that workqueue worker tasks may process unlimited
  number of work items back-to-back without every yielding inbetween.
  This usually isn't noticeable but a work item which re-queues itself
  waiting for someone else to do something can deadlock with
  stop_machine.  stop_machine will ensure nothing else happens on all
  other cpus and the requeueing work item will reqeueue itself
  indefinitely without ever yielding and thus preventing the CPU from
  entering stop_machine.

  Kudos to Jamie Liu for spotting and diagnosing the problem.  This can
  be trivially fixed by adding cond_resched() after processing each work
  item"

* 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: cond_resched() after processing each work item
This commit is contained in:
Linus Torvalds 2013-08-29 17:02:48 -07:00
commit ff49745263
1 changed files with 9 additions and 0 deletions
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9
kernel/workqueue.c
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@ -2201,6 +2201,15 @@ __acquires(&pool->lock)
dump_stack();
}
/*
* The following prevents a kworker from hogging CPU on !PREEMPT
* kernels, where a requeueing work item waiting for something to
* happen could deadlock with stop_machine as such work item could
* indefinitely requeue itself while all other CPUs are trapped in
* stop_machine.
*/
cond_resched();
spin_lock_irq(&pool->lock);
/* clear cpu intensive status */