From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH tip/core/rcu 21/21] drivers/vhost: Remove now-redundant
	read_barrier_depends()
Date: Tue, 5 Dec 2017 20:57:52 +0100
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To: "Michael S. Tsirkin" <mst@redhat.com>
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On Tue, Dec 05, 2017 at 09:51:48PM +0200, Michael S. Tsirkin wrote:
> > > WRITE_ONCE(obj->val, 1);
> > > smp_wmb();
> > > WRITE_ONCE(*foo, obj);
> > 
> > I believe Peter was instead suggesting:
> > 
> > WRITE_ONCE(obj->val, 1);
> > smp_store_release(foo, obj);
> 
> Isn't that more expensive though?

Depends on the architecture. The only architecture where it is more
expensive and people actually still care about is ARM I think.