Re: [RFC/PATCH] debug workqueue deadlocks with lockdep

[Ingo Molnar]

* Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> Now we have a false positive if some time we queue B into that 
> workqueue, and this is not good.
> 
> We can avoid this problem if we put lockdep_map into work_struct, so 
> that wait_on_work() "locks" work->lockdep_map, while flush_workqueue() 
> takes wq->lockdep_map.
> 
> But probably we don't need this right now, at least until we really 
> have a lot of false positives while converting from flush_workqueue() 
> to cancel_work_sync/cancel_delayed_work_sync.

would be nice to map the real dependencies. Adding another lockdep_map 
is really low-cost and the lack of false positives is reassuring.

	Ingo
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