From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH -v3 3/8] locking: Introduce smp_acquire__after_ctrl_dep
Date: Wed, 1 Jun 2016 18:22:55 +0200
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 <20160601135214.GC30064@insomnia>
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Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
	manfred@colorfullife.com, dave@stgolabs.net,
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To: Boqun Feng <boqun.feng@gmail.com>
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On Wed, Jun 01, 2016 at 09:52:14PM +0800, Boqun Feng wrote:
> On Tue, May 31, 2016 at 11:41:37AM +0200, Peter Zijlstra wrote:

> > @@ -292,7 +282,7 @@ static void sem_wait_array(struct sem_ar
> >  		sem = sma->sem_base + i;
> >  		spin_unlock_wait(&sem->lock);
> >  	}
> > -	ipc_smp_acquire__after_spin_is_unlocked();
> > +	smp_acquire__after_ctrl_dep();
> 
> I wonder whether we can kill this barrier after updating
> spin_unlock_wait() to ACQUIRE?

See patch 5 doing that :-)