Re: workqueue deadlock

[Ingo Molnar]

* Andrew Morton <akpm@xxxxxxxx> wrote:

> > > +		if (cpu != -1)
> > > +			mutex_lock(&workqueue_mutex);
> > 
> > events/4 thread itself wanting the same mutex above?
> 
> Could do, not sure.  I'm planning on converting all the locking around 
> here to preempt_disable() though.

please at least use an owner-recursive per-CPU lock, not a naked 
preempt_disable()! The concurrency rules for data structures changed via 
preempt_disable() are quite hard to sort out after the fact. 
(preempt_disable() is too opaque, it doesnt attach data structure to 
critical section, like normal locks do.)

	Ingo
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