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);