Messages in this thread | | | Date | Fri, 20 Apr 2012 15:18:00 +0800 | From | Yong Zhang <> | Subject | Re: [PATCH 1/2] workqueue: Catch more locking problems with flush_work() |
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On Thu, Apr 19, 2012 at 11:26:47PM -0700, Stephen Boyd wrote: > complain in the case where the work is not queued. That case is not a > false positive. We will get a lockdep warning if the work is running
IIRC, flush_work() is just a nop when a work is not queued nor running.
> (when start_flush_work() returns true) solely with the > lock_map_acquire() on cwq->wq->lockdep_map.
Yeah, that is the point we use lockdep to detect deadlock for workqueue.
But when looking at start_flush_work(), for some case !(cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER), lock_map_acquire_read() is called, but recursive read is not added to the chain list. So when lock_map_acquire_read(&cwq->wq->lockdep_map) is called, deadlock will not be detected. I hope you don't hit that special case.
Thanks, Yong
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