Re: [PATCH 5/8] locking, mutex: Cancelable MCS lock for adaptive spinning

[Jason Low]

On Wed, 2014-02-26 at 10:22 +0100, Peter Zijlstra wrote:
> On Tue, Feb 25, 2014 at 11:56:19AM -0800, Jason Low wrote:
> > On Mon, 2014-02-10 at 20:58 +0100, Peter Zijlstra wrote:
> > > +	for (;;) {
> > > +		if (prev->next == node &&
> > > +		    cmpxchg(&prev->next, node, NULL) == node)
> > > +			break;
> > > +
> > > +		/*
> > > +		 * We can only fail the cmpxchg() racing against an unlock(),
> > > +		 * in which case we should observe @node->locked becomming
> > > +		 * true.
> > > +		 */
> > > +		if (smp_load_acquire(&node->locked))
> > > +			return true;
> 
> I've stuck on in right about here. So that we don't unduly delay the
> cmpxchg() after the load of prev.

Ok.

Reviewed-by: Jason Low <jason.low2@xxxxxx>


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