linux-kernel - Re: Unlock-lock questions and the Linux Kernel Memory Model

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Message-ID: <20171130162501.cx5ha7nispozlf34@hirez.programming.kicks-ass.net>
Date:   Thu, 30 Nov 2017 17:25:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Daniel Lustig <dlustig@...dia.com>,
        Andrea Parri <parri.andrea@...il.com>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Jade Alglave <j.alglave@....ac.uk>,
        Boqun Feng <boqun.feng@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Will Deacon <will.deacon@....com>,
        David Howells <dhowells@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Unlock-lock questions and the Linux Kernel Memory Model

On Thu, Nov 30, 2017 at 08:14:01AM -0800, Paul E. McKenney wrote:
> > (Also, technically speaking, the litmus test doesn't have any release 
> > operations, so no release sequence...)
> 
> True!  But if you translated it into C11, you would probably turn the
> smp_wmb() followed by write into a store release, which would get you
> a release sequence.

	smp_wmb()
	WRITE_ONCE(*y, 1);

does not a RELEASE make.