Re: [PATCH v5] locking/rwsem: Make handoff bit handling more consistent

[Waiman Long]

On 4/11/22 17:03, john.p.donnelly@xxxxxxxxxx wrote:
> > > I have reached out to Waiman and he suggested this for our next test 
> > > pass:
> > >
> > >
> > > 1ee326196c6658 locking/rwsem: Always try to wake waiters in 
> > > out_nolock path
> >
> > Does this commit help to avoid the lockup problem?
> >
> > Commit 1ee326196c6658 fixes a potential missed wakeup problem when a 
> > reader first in the wait queue is interrupted out without acquiring 
> > the lock. It is actually not a fix for commit d257cc8cb8d5. However, 
> > this commit changes the out_nolock path behavior of writers by 
> > leaving the handoff bit set when the wait queue isn't empty. That 
> > likely makes the missed wakeup problem easier to reproduce.
> >
> > Cheers,
> > Longman
>
> Hi,
>
>
> We are testing now
>
> ETA for fio soak test completion is  ~15hr from now.
>
> I wanted to share the stack traces for future reference + occurrences.
I am looking forward to your testing results tomorrow.

Cheers,
Longman