Messages in this thread | | | Date | Wed, 30 Aug 2017 16:41:17 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation |
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On Wed, Aug 30, 2017 at 11:09:53AM +0900, Byungchul Park wrote: > On Tue, Aug 29, 2017 at 10:59:39AM +0200, Peter Zijlstra wrote: > > Subject: lockdep: Untangle xhlock history save/restore from task independence > > > > Where XHLOCK_{SOFT,HARD} are save/restore points in the xhlocks[] to > > ensure the temporal IRQ events don't interact with task state, the > > XHLOCK_PROC is a fundament different beast that just happens to share > > the interface. > > > > The purpose of XHLOCK_PROC is to annotate independent execution inside > > one task. For example workqueues, each work should appear to run in its > > own 'pristine' 'task'. > > > > Remove XHLOCK_PROC in favour of its own interface to avoid confusion. > > Much better to me than the patch you did previously, but, see blow. > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > > index c0331891dec1..ab3c0dc8c7ed 100644 > > --- a/kernel/workqueue.c > > +++ b/kernel/workqueue.c > > @@ -2107,14 +2107,14 @@ __acquires(&pool->lock) > > * Which would create W1->C->W1 dependencies, even though there is no > > * actual deadlock possible. There are two solutions, using a > > * read-recursive acquire on the work(queue) 'locks', but this will then > > - * hit the lockdep limitation on recursive locks, or simly discard > > + * hit the lockdep limitation on recursive locks, or simply discard > > * these locks. > > * > > * AFAICT there is no possible deadlock scenario between the > > * flush_work() and complete() primitives (except for single-threaded > > * workqueues), so hiding them isn't a problem. > > */ > > - crossrelease_hist_start(XHLOCK_PROC, true); > > + lockdep_invariant_state(true); > > This is what I am always curious about. It would be ok if you agree with > removing this work-around after fixing acquire things in wq. But, you > keep to say this is essencial. > > You should focus on what dependencies actually are, than saparating > contexts unnecessarily. Of course, we have to do it for each work, _BUT_ > not between outside of work and each work since there might be > dependencies between them certainly.
You have never answered it. I'm curious about your answer. If you can't, I think you have to revert all your patches. All yours are wrong.
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