From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v6 4/5] MCS Lock: Barrier corrections
Date: Thu, 21 Nov 2013 05:18:06 -0800
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To: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>, Will Deacon <will.deacon@arm.com>, Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Waiman Long <waiman.long@hp.com>, Andrea Arcangeli <aarcange@redhat.com>, Alex Shi <alex.shi@linaro.org>, Andi Kleen <andi@firstfloor.org>, Michel Lespinasse <walken@google.com>, Davidlohr Bueso <davidlohr.bueso@hp.com>, Matthew R Wilcox <matthew.r.wilcox@intel.com>, Dave Hansen <dave.hansen@intel.com>, Rik van Riel <riel@redhat.com>, Peter Hurley <peter@hurleysoftware.com>, Raghavendra
List-Id: linux-arch.vger.kernel.org

On Thu, Nov 21, 2013 at 11:45:03AM +0100, Peter Zijlstra wrote:
> On Wed, Nov 20, 2013 at 08:53:33PM -0800, Paul E. McKenney wrote:
> > The other option is to weaken lock semantics so that unlock-lock no
> > longer implies a full barrier, but I believe that we would regret taking
> > that path.  (It would be OK by me, I would just add a few smp_mb()
> > calls on various slowpaths in RCU.  But...)
> 
> Please no, I know we rely on it in a number of places, I just can't
> remember where all those were :/

;-) ;-) ;-)

Yeah, I would also have to overprovision smp_mb()s in a number of
places.  Then again, I know that I don't rely on this on any of
RCU's fastpaths.

							Thanx, Paul

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