linux-kernel - Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt notion of relaxed

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Message-ID: <20200902124725.GF1362448@hirez.programming.kicks-ass.net>
Date:   Wed, 2 Sep 2020 14:47:25 +0200
From:   peterz@...radead.org
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     paulmck@...nel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        stern@...land.harvard.edu, parri.andrea@...il.com, will@...nel.org,
        npiggin@...il.com, dhowells@...hat.com, j.alglave@....ac.uk,
        luc.maranget@...ia.fr, akiyks@...il.com
Subject: Re: [PATCH kcsan 6/9] tools/memory-model: Expand the cheatsheet.txt
 notion of relaxed

On Wed, Sep 02, 2020 at 08:37:15PM +0800, Boqun Feng wrote:
> On Wed, Sep 02, 2020 at 12:14:12PM +0200, peterz@...radead.org wrote:

> > > To be accurate, atomic_set() doesn't return any value, so it cannot be
> > > ordered against DR and DW ;-)
> > 
> > Surely DW is valid for any store.
> > 
> 
> IIUC, the DW colomn stands for whether the corresponding operation (in
> this case, it's atomic_set()) is ordered any write that depends on this
> operation. I don't think there is a write->write dependency, so DW for
> atomic_set() should not be Y, just as the DW for WRITE_ONCE().

Ah, just shows I can't read I suppose ;-) I thought we were talking of
the other side of the depency.