linux-kernel - Re: [RFC v2 3/4] Documentation/locking/atomic: Add a litmus test for atomic

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Date:   Thu, 20 Feb 2020 08:27:17 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     linux-kernel@...r.kernel.org,
        Andrea Parri <parri.andrea@...il.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Akira Yokosawa <akiyks@...il.com>,
        Daniel Lustig <dlustig@...dia.com>,
        Jonathan Corbet <corbet@....net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [RFC v2 3/4] Documentation/locking/atomic: Add a litmus test for
 atomic_set()

On Wed, Feb 19, 2020 at 10:07:09AM -0500, Alan Stern wrote:
> On Wed, 19 Feb 2020, Boqun Feng wrote:
> 
> > We already use a litmus test in atomic_t.txt to describe the behavior of
> > an atomic_set() with the an atomic RMW, so add it into atomic-tests
> > directory to make it easily accessible for anyone who cares about the
> > semantics of our atomic APIs.
> > 
> > Additionally, change the sentences describing the test in atomic_t.txt
> > with better wording.
> 
> One very minor point about the new working in atomic_t.txt:
> 
> > diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
> > index ceb85ada378e..d30cb3d87375 100644
> > --- a/Documentation/atomic_t.txt
> > +++ b/Documentation/atomic_t.txt
> > @@ -85,10 +85,10 @@ smp_store_release() respectively. Therefore, if you find yourself only using
> >  the Non-RMW operations of atomic_t, you do not in fact need atomic_t at all
> >  and are doing it wrong.
> >  
> > -A subtle detail of atomic_set{}() is that it should be observable to the RMW
> > -ops. That is:
> > +A note for the implementation of atomic_set{}() is that it cannot break the
> > +atomicity of the RMW ops. That is:
> 
> This would be slightly better if you changed it to: "it must not break".
> 

Got it. Indeed it's the better wording, thanks!

Regards,
Boqun

> The comments in the litmus test and README file are okay as they stand.
> 
> Alan
>