Re: [RFC][PATCH 1/3] locking/mutex: Rework mutex::owner

[Peter Zijlstra]

On Wed, Aug 24, 2016 at 10:56:59AM +0100, Will Deacon wrote:
> > +   owner = atomic_long_read(&lock->owner);
> > +   for (;;) {
> > +           unsigned long old;
> > +
> > +           old = atomic_long_cmpxchg_release(&lock->owner, owner, owner & 
> > 0x03);
> > +           if (old == owner)
> > +                   break;
> > +
> > +           owner = old;
> > +   }
> 
> Can you rewrite this using atomic_long_fetch_and_release?

Yes, until patch 3/3.. but now that you mention it I think we can do:

        owner = atomic_long_read(&lock->owner);
        if (!(owner & MUTEX_FLAG_HANDOFF))
                (void)atomic_long_fetch_and_release(MUTEX_FLAGS, &lock->owner);