On Fri, Aug 25, 2017 at 06:34:43AM -0700, Tejun Heo wrote:
> On Fri, Aug 25, 2017 at 05:41:03PM +0900, Byungchul Park wrote:
> > Hello all,
> >
> > This is _RFC_.
> >
> > I want to request for comments about if it's reasonable conceptually. If
> > yes, I want to resend after working it more carefully.
> >
> > Could you let me know your opinions about this?
> >
> > ----->8-----
> > From 448360c343477fff63df766544eec4620657a59e Mon Sep 17 00:00:00 2001
> > From: Byungchul Park <[email protected]>
> > Date: Fri, 25 Aug 2017 17:35:07 +0900
> > Subject: [RFC] workqueue: remove manual lockdep uses to detect deadlocks
> >
> > We introduced the following commit to detect deadlocks caused by
> > wait_for_completion() in flush_{workqueue, work}() and other locks. But
> > now LOCKDEP_COMPLETIONS is introduced, such works are automatically done
> > by LOCKDEP_COMPLETIONS. So it doesn't have to be done manually anymore.
> > Removed it.
>
> I'm not following lockdep development, so can't really comment but if
> you're saying that wq can retain the same level of protection while
> not having explicit annotations, conceptually, it's of course great.
> However, how would it distinguish things like flushing another work
> item on a workqueue w/ max_active of 1?
Do you mean the following?
process_one_work()
acquire(W1) <---------+- distinguishable?
work->fn() |
flush_work(W2) |
acquire(W2) <---+
release(W2)
release(W1)
