linux-kernel - Re: [PATCH] tools/memory-model: remove rb-dep, smp_read_barrier_depends, and lockless

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Message-ID: <Pine.LNX.4.44L0.1802210958520.2032-100000@iolanthe.rowland.org>
Date:   Wed, 21 Feb 2018 10:00:20 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:     Andrea Parri <parri.andrea@...il.com>,
        Akira Yokosawa <akiyks@...il.com>,
        Kernel development list <linux-kernel@...r.kernel.org>,
        <mingo@...nel.org>, Will Deacon <will.deacon@....com>,
        <peterz@...radead.org>, <boqun.feng@...il.com>,
        <npiggin@...il.com>, <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Patrick Bellasi <patrick.bellasi@....com>
Subject: Re: [PATCH] tools/memory-model: remove rb-dep, smp_read_barrier_depends,
 and lockless_dereference

On Fri, 16 Feb 2018, Paul E. McKenney wrote:

> On Fri, Feb 16, 2018 at 05:22:55PM -0500, Alan Stern wrote:
> > Since commit 76ebbe78f739 ("locking/barriers: Add implicit
> > smp_read_barrier_depends() to READ_ONCE()") was merged for the 4.15
> > kernel, it has not been necessary to use smp_read_barrier_depends().
> > Similarly, commit 59ecbbe7b31c ("locking/barriers: Kill
> > lockless_dereference()") removed lockless_dereference() from the
> > kernel.
> > 
> > Since these primitives are no longer part of the kernel, they do not
> > belong in the Linux Kernel Memory Consistency Model.  This patch
> > removes them, along with the internal rb-dep relation, and updates the
> > revelant documentation.
> > 
> > Signed-off-by: Alan Stern <stern@...land.harvard.edu>
> 
> I queued this, but would welcome an update that addressed Akira's
> feedback as appropriate.

Is it too late to send a v2 of this patch?  I didn't want to do it 
before now because the issue raised by Andrea wasn't settled.  (Some 
could claim that it still isn't fully settled...)

Alan