diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-08-29 17:02:48 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-08-29 17:02:48 -0700 |
commit | ff497452636f4687e517964817b7e2bd99f4b44b (patch) | |
tree | a02fd3216941b71ea58c6b57f84344be64168301 | |
parent | 06a557f7a68e126181f09831cb2fac6f7a7f43c2 (diff) | |
parent | b22ce2785d97423846206cceec4efee0c4afd980 (diff) |
Merge branch 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
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
-rw-r--r-- | kernel/workqueue.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 7f5d4be22034..e93f7b9067d8 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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 */ |