From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S933745AbcIFLLB (ORCPT <rfc822;w@1wt.eu>);
        Tue, 6 Sep 2016 07:11:01 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:49484 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1754927AbcIFLK7 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 6 Sep 2016 07:10:59 -0400
Date: Tue, 6 Sep 2016 13:10:52 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        USB list <linux-usb@vger.kernel.org>,
        Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Memory barrier needed with wake_up_process()?
Message-ID: <20160906111052.GZ10121@twins.programming.kicks-ass.net>
References: <20160902191857.GL10153@twins.programming.kicks-ass.net>
 <Pine.LNX.4.44L0.1609021526420.2027-100000@iolanthe.rowland.org>
 <20160902221413.GN10153@twins.programming.kicks-ass.net>
 <20160902221629.GK10168@twins.programming.kicks-ass.net>
 <20160905094310.GB2649@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160905094310.GB2649@arm.com>
User-Agent: Mutt/1.5.23.1 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Sep 05, 2016 at 10:43:11AM +0100, Will Deacon wrote:
> On Sat, Sep 03, 2016 at 12:16:29AM +0200, Peter Zijlstra wrote:

> > Forgot to Cc Will. Will, does ARM64 need to make smp_mb__before_spinlock
> > smp_mb() too?
> 
> Yes, probably. Just to confirm, the test is something like:
> 
> 
> CPU0
> ----
> 
> Wx=1
> smp_mb__before_spinlock()
> LOCK(y)
> Rz=0
> 
> CPU1
> ----
> 
> Wz=1
> smp_mb()
> Rx=0
> 
> 
> and that should be forbidden?

Indeed.