From: "Paul E. McKenney" <paulmck@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org,
"E."@paulmck-thinkpad-p17-gen-1.smtp.subspace.kernel.org,
Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <parri.andrea@gmail.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
Paul@paulmck-thinkpad-p17-gen-1.smtp.subspace.kernel.org,
Akira Yokosawa <akiyks@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
Joel Fernandes <joel@joelfernandes.org>,
Jonathan Corbet <corbet@lwn.net>,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
Anna-Maria Behnsen <anna-maria@linutronix.de>
Subject: Re: [PATCH doc] Emphasize that failed atomic operations give no ordering
Date: Tue, 30 Jan 2024 09:58:39 -0800 [thread overview]
Message-ID: <5feeddda-f000-4b83-9981-e422c0d04881@paulmck-laptop> (raw)
In-Reply-To: <Zbkt94Q8a-xFXrve@FVFF77S0Q05N>
On Tue, Jan 30, 2024 at 05:12:23PM +0000, Mark Rutland wrote:
> On Tue, Jan 30, 2024 at 06:53:38AM -0800, Paul E. McKenney wrote:
> > The ORDERING section of Documentation/atomic_t.txt can easily be read as
> > saying that conditional atomic RMW operations that fail are ordered when
> > those operations have the _acquire() or _release() prefixes. This is
> > not the case, therefore update this section to make it clear that failed
> > conditional atomic RMW operations provide no ordering.
> >
> > Reported-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > Cc: Alan Stern <stern@rowland.harvard.edu>
> > Cc: Andrea Parri <parri.andrea@gmail.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Boqun Feng <boqun.feng@gmail.com>
> > Cc: Nicholas Piggin <npiggin@gmail.com>
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Jade Alglave <j.alglave@ucl.ac.uk>
> > Cc: Luc Maranget <luc.maranget@inria.fr>
> > Cc: "Paul E. McKenney" <paulmck@kernel.org>
> > Cc: Akira Yokosawa <akiyks@gmail.com>
> > Cc: Daniel Lustig <dlustig@nvidia.com>
> > Cc: Joel Fernandes <joel@joelfernandes.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Jonathan Corbet <corbet@lwn.net>
> > Cc: <linux-arch@vger.kernel.org>
> > Cc: <linux-doc@vger.kernel.org>
> >
> > diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
> > index d7adc6d543db4..bee3b1bca9a7b 100644
> > --- a/Documentation/atomic_t.txt
> > +++ b/Documentation/atomic_t.txt
> > @@ -171,14 +171,14 @@ The rule of thumb:
> > - RMW operations that are conditional are unordered on FAILURE,
> > otherwise the above rules apply.
> >
> > -Except of course when an operation has an explicit ordering like:
> > +Except of course when a successful operation has an explicit ordering like:
> >
> > {}_relaxed: unordered
> > {}_acquire: the R of the RMW (or atomic_read) is an ACQUIRE
> > {}_release: the W of the RMW (or atomic_set) is a RELEASE
> >
> > Where 'unordered' is against other memory locations. Address dependencies are
> > -not defeated.
> > +not defeated. Conditional operations are still unordered on FAILURE.
> >
> > Fully ordered primitives are ordered against everything prior and everything
> > subsequent. Therefore a fully ordered primitive is like having an smp_mb()
> >
>
> FWIW:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
Applied, thank you!
Thanx, Paul
prev parent reply other threads:[~2024-01-30 17:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 14:53 [PATCH doc] Emphasize that failed atomic operations give no ordering Paul E. McKenney
2024-01-30 16:02 ` Andrea Parri
2024-01-30 16:33 ` Paul E. McKenney
2024-01-30 17:12 ` Mark Rutland
2024-01-30 17:58 ` Paul E. McKenney [this message]
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