Messages in this thread | | | Date | Fri, 20 Apr 2012 01:18:19 -0700 | From | Stephen Boyd <> | Subject | Re: [PATCH 1/2] workqueue: Catch more locking problems with flush_work() |
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On 4/20/2012 12:18 AM, Yong Zhang wrote: > 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.
Agreed, but it's better to always print a lockdep warning instead of only when the deadlock is going to occur.
> >> (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.
Hmm. Originally I had what you suggested in my patch but I left it out because I wasn't sure if it would cause false positives. Do you see any possibility for false positives? I'll add it back in if not.
-- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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