linux-kernel - Re: [PATCH -v3 3/8] locking: Introduce smp_acquire__after_ctrl

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Message-ID: <20160601162255.GT3190@twins.programming.kicks-ass.net>
Date:	Wed, 1 Jun 2016 18:22:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Boqun Feng <boqun.feng@...il.com>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	manfred@...orfullife.com, dave@...olabs.net,
	paulmck@...ux.vnet.ibm.com, will.deacon@....com,
	Waiman.Long@....com, tj@...nel.org, pablo@...filter.org,
	kaber@...sh.net, davem@...emloft.net, oleg@...hat.com,
	netfilter-devel@...r.kernel.org, sasha.levin@...cle.com,
	hofrat@...dl.org
Subject: Re: [PATCH -v3 3/8] locking: Introduce smp_acquire__after_ctrl_dep

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 :-)