On Wed, Aug 30, 2017 at 06:24:39PM +0900, Byungchul Park wrote:
> > -----Original Message-----
> > From: Peter Zijlstra [mailto:pet...@infradead.org]
> > Sent: Wednesday, August 30, 2017 6:12 PM
> > To: Byungchul Park
> > Cc: mi...@kernel.org; t...@kernel.org; boqun.f...@gmail.com;
> > da...@fromorbit.com; johan...@sipsolutions.net; o...@redhat.com; linux-
> > ker...@vger.kernel.org; kernel-t...@lge.com
> > Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation
> >
> > On Wed, Aug 30, 2017 at 06:01:59PM +0900, Byungchul Park wrote:
> > > My point is that we inevitably lose valuable dependencies by yours.
> > That's
> > > why I've endlessly asked you 'do you have any reason you try those
> > patches?'
> > > a ton of times. And you have never answered it.
> >
> > The only dependencies that are lost are those between the first work and
> > the setup of the workqueue thread.
> >
> > And there obviously _should_ not be any dependencies between those. A
>
> 100% right. Since there obviously should not be any, it would be better
> to check them. So I've endlessly asked you 'do you have any reason removing
> the opportunity for that check?'. Overhead? Logical problem? Or want to
> believe workqueue setup code perfect forever? I mean, is it a problem if we
> check them?
>
> > work should not depend on the setup of the thread.
>
> 100% right.
For example - I'm giving you the same example repeatedly:
context X context Y
--------- ---------
wait_for_completion(C)
acquire(A)
process_one_work()
acquire(B)
work->fn()
complete(C)
Please check C->A and C->B.
