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SubjectRe: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation
On Fri, Sep 01, 2017 at 11:05:12AM +0900, Byungchul Park wrote:
> On Thu, Aug 31, 2017 at 10:34:53AM +0200, Peter Zijlstra wrote:
> > On Thu, Aug 31, 2017 at 05:15:01PM +0900, Byungchul Park wrote:
> > > It's not important. Ok, check the following, instead:
> > >
> > > context X context Y
> > > --------- ---------
> > > wait_for_completion(C)
> > > acquire(A)
> > > release(A)
> > > process_one_work()
> > > acquire(B)
> > > release(B)
> > > work->fn()
> > > complete(C)
> > >
> > > We don't need to lose C->A and C->B dependencies unnecessarily.
> >
> > I really can't be arsed about them. Its really only the first few works
> > that will retain that dependency anyway, even if you were to retain
> > them.
>
> Wrong.
>
> Every 'work' doing complete() for different classes of completion
> variable suffers from losing valuable dependencies, every time, not
> first few ones.

The moment you overrun the history array its gone. So yes, only the
first few works will ever see them

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