From: Alan Stern <stern@rowland.harvard.edu>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-team@meta.com, mingo@kernel.org, parri.andrea@gmail.com,
will@kernel.org, peterz@infradead.org, boqun.feng@gmail.com,
npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk,
luc.maranget@inria.fr, akiyks@gmail.com,
Frederic Weisbecker <frederic@kernel.org>,
Daniel Lustig <dlustig@nvidia.com>,
Joel Fernandes <joel@joelfernandes.org>,
Mark Rutland <mark.rutland@arm.com>,
Jonathan Corbet <corbet@lwn.net>,
linux-doc@vger.kernel.org
Subject: Re: [PATCH memory-model 2/4] Documentation/litmus-tests: Demonstrate unordered failing cmpxchg
Date: Mon, 6 May 2024 15:21:54 -0400 [thread overview]
Message-ID: <c168f56f-dfae-4cac-bc61-fc5a93ee3aed@rowland.harvard.edu> (raw)
In-Reply-To: <2a695f63-6c9a-4837-ac03-f0a5c63daaaf@paulmck-laptop>
On Mon, May 06, 2024 at 11:00:42AM -0700, Paul E. McKenney wrote:
> On Mon, May 06, 2024 at 06:30:45PM +0200, Jonas Oberhauser wrote:
> > Am 5/6/2024 um 12:05 PM schrieb Jonas Oberhauser:
> > > Am 5/2/2024 um 1:21 AM schrieb Paul E. McKenney:
> > > > This commit adds four litmus tests showing that a failing cmpxchg()
> > > > operation is unordered unless followed by an smp_mb__after_atomic()
> > > > operation.
> > >
> > > So far, my understanding was that all RMW operations without suffix
> > > (xchg(), cmpxchg(), ...) will be interpreted as F[Mb];...;F[Mb].
It's more accurate to say that RMW operations without a suffix that
return a value will be interpreted that way. So for example,
atomic_inc() doesn't imply any ordering, because it doesn't return a
value.
> > > barriers explicitly inside the cat model, instead of relying on implicit
> > > conversions internal to herd.
Don't the annotations in linux-kernel.def and linux-kernel.bell (like
"noreturn") already make this explicit?
I guess the part that is still implicit is that herd7 doesn't regard
failed RMW operations as actual RMWs (they don't have a store part).
Alan
next prev parent reply other threads:[~2024-05-06 19:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-04 19:26 [PATCH memory-model 0/3] LKMM updates for v6.10 Paul E. McKenney
2024-04-04 19:26 ` [PATCH memory-model 1/3] Documentation/litmus-tests: Add locking tests to README Paul E. McKenney
2024-04-04 19:26 ` [PATCH memory-model 2/3] Documentation/litmus-tests: Demonstrate unordered failing cmpxchg Paul E. McKenney
2024-04-05 10:05 ` Andrea Parri
2024-04-08 20:46 ` Paul E. McKenney
2024-04-09 10:43 ` Andrea Parri
2024-04-04 19:26 ` [PATCH memory-model 3/3] Documentation/atomic_t: Emphasize that failed atomic operations give no ordering Paul E. McKenney
2024-05-01 23:21 ` [PATCH v2 memory-model 0/3] LKMM updates for v6.10 Paul E. McKenney
2024-05-01 23:21 ` [PATCH memory-model 1/4] Documentation/litmus-tests: Add locking tests to README Paul E. McKenney
2024-05-01 23:21 ` [PATCH memory-model 2/4] Documentation/litmus-tests: Demonstrate unordered failing cmpxchg Paul E. McKenney
2024-05-06 10:05 ` Jonas Oberhauser
2024-05-06 16:30 ` Jonas Oberhauser
2024-05-06 18:00 ` Paul E. McKenney
2024-05-06 19:21 ` Alan Stern [this message]
2024-05-07 9:03 ` Jonas Oberhauser
2024-05-08 1:17 ` Andrea Parri
2024-05-07 9:11 ` Jonas Oberhauser
2024-05-15 6:44 ` Hernan Ponce de Leon
2024-05-15 15:01 ` Paul E. McKenney
2024-05-01 23:21 ` [PATCH memory-model 3/4] Documentation/atomic_t: Emphasize that failed atomic operations give no ordering Paul E. McKenney
2024-05-01 23:21 ` [PATCH memory-model 4/4] Documentation/litmus-tests: Make cmpxchg() tests safe for klitmus Paul E. McKenney
2024-05-02 9:36 ` [PATCH v2 memory-model 0/3] LKMM updates for v6.10 Andrea Parri
2024-05-02 13:46 ` Paul E. McKenney
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