Re: [PATCH v3 1/3] lockdep: Make LOCKDEP_CROSSRELEASE configs all part of PROVE_LOCKING

[Byungchul Park]

On Thu, Aug 24, 2017 at 03:11:53PM +0900, Byungchul Park wrote:
> On Wed, Aug 23, 2017 at 07:47:14PM +0200, Peter Zijlstra wrote:
> > Those are fine and are indeed the flush_work() vs work inversion.
> > 
> > The two straight forward annotations are:
> > 
> > flush_work(work)	process_one_work(wq, work)
> >   A(work)		  A(work)
> >   R(work)		  work->func(work);
> > 			  R(work)
> > 
> > Which catches:
> > 
> > Task-1:			work:
> > 
> >   mutex_lock(&A);	mutex_lock(&A);
> >   flush_work(work);
> 
> I'm not sure but, with LOCKDEP_COMPLETE enabled, this issue would
> automatically be covered w/o additional A(work)/R(work). Right?
> 
> A(work)/R(work) seem to be used for preventing wait_for_completion()
> in flush_work() from waiting for the completion forever because of the
> work using mutex_lock(&A). Am I understanding correctly?
> 
> If yes, we can use just LOCKDEP_COMPLETE for that purpose.

I'm not familiar with workqueue but, the manual lockdep_map_acquire() in
workqueue code seems to be introduced to do what LOCKDEP_COMPLETE does
for wait_for_completion() and complete().

Wrong?