From: Boqun Feng <boqun.feng@gmail.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-kernel@vger.kernel.org,
Andrea Parri <parri.andrea@gmail.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@kernel.org>,
Akira Yokosawa <akiyks@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
Jonathan Corbet <corbet@lwn.net>,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [RFC 2/3] tools/memory-model: Add a litmus test for atomic_set()
Date: Sat, 15 Feb 2020 07:52:15 +0800 [thread overview]
Message-ID: <20200214235215.GB110915@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> (raw)
In-Reply-To: <Pine.LNX.4.44L0.2002141028280.1579-100000@iolanthe.rowland.org>
On Fri, Feb 14, 2020 at 10:47:48AM -0500, Alan Stern wrote:
> On Fri, 14 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 the litmus-tests
> > directory to make it easily accessible for anyone who cares about the
> > semantics of our atomic APIs.
> >
> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> > ---
> > .../Atomic-set-observable-to-RMW.litmus | 24 +++++++++++++++++++
> > tools/memory-model/litmus-tests/README | 3 +++
> > 2 files changed, 27 insertions(+)
> > create mode 100644 tools/memory-model/litmus-tests/Atomic-set-observable-to-RMW.litmus
>
> I don't like that name, or the corresponding sentence in atomic_t.txt:
>
> A subtle detail of atomic_set{}() is that it should be
> observable to the RMW ops.
>
> "Observable" doesn't get the point across -- the point being that the
> atomic RMW ops have to be _atomic_ with respect to all atomic store
> operations, including atomic_set.
>
> Suggestion: Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus, with
> corresponding changes to the comment in the litmus test and the entry
> in README.
>
I agree, and thanks for the suggestion! And I change the sentence in
atomic_t.txt with:
A note for the implementation of atomic_set{}() is that it
cannot break the atomicity of the RMW ops.
, since I think that part of the doc is more about the suggestion to
anyone who want to implement the atomic_set(). Peter, is that OK to you?
Regards,
Boqun
> Alan
>
> > diff --git a/tools/memory-model/litmus-tests/Atomic-set-observable-to-RMW.litmus b/tools/memory-model/litmus-tests/Atomic-set-observable-to-RMW.litmus
> > new file mode 100644
> > index 000000000000..4326f56f2c1a
> > --- /dev/null
> > +++ b/tools/memory-model/litmus-tests/Atomic-set-observable-to-RMW.litmus
> > @@ -0,0 +1,24 @@
> > +C Atomic-set-observable-to-RMW
> > +
> > +(*
> > + * Result: Never
> > + *
> > + * Test of the result of atomic_set() must be observable to atomic RMWs.
> > + *)
> > +
> > +{
> > + atomic_t v = ATOMIC_INIT(1);
> > +}
> > +
> > +P0(atomic_t *v)
> > +{
> > + (void)atomic_add_unless(v,1,0);
> > +}
> > +
> > +P1(atomic_t *v)
> > +{
> > + atomic_set(v, 0);
> > +}
> > +
> > +exists
> > +(v=2)
> > diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README
> > index 681f9067fa9e..81eeacebd160 100644
> > --- a/tools/memory-model/litmus-tests/README
> > +++ b/tools/memory-model/litmus-tests/README
> > @@ -2,6 +2,9 @@
> > LITMUS TESTS
> > ============
> >
> > +Atomic-set-observable-to-RMW.litmus
> > + Test of the result of atomic_set() must be observable to atomic RMWs.
> > +
> > CoRR+poonceonce+Once.litmus
> > Test of read-read coherence, that is, whether or not two
> > successive reads from the same variable are ordered.
> >
>
next prev parent reply other threads:[~2020-02-14 23:52 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 4:01 [RFC 0/3] tools/memory-model: Add litmus tests for atomic APIs Boqun Feng
2020-02-14 4:01 ` [RFC 1/3] Documentation/locking/atomic: Fix atomic-set litmus test Boqun Feng
2020-02-14 4:01 ` [RFC 2/3] tools/memory-model: Add a litmus test for atomic_set() Boqun Feng
2020-02-14 8:12 ` Andrea Parri
2020-02-14 10:40 ` Boqun Feng
2020-02-25 7:34 ` Boqun Feng
2020-02-25 13:01 ` Luc Maranget
2020-02-25 21:42 ` More on reader-writer locks Alan Stern
2020-02-26 9:46 ` Luc Maranget
2020-02-26 2:51 ` [RFC 2/3] tools/memory-model: Add a litmus test for atomic_set() Boqun Feng
2020-02-14 15:47 ` Alan Stern
2020-02-14 23:52 ` Boqun Feng [this message]
2020-02-17 11:02 ` Peter Zijlstra
2020-02-14 4:01 ` [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic() Boqun Feng
2020-02-14 6:15 ` Boqun Feng
2020-02-14 8:18 ` Andrea Parri
2020-02-14 8:20 ` Boqun Feng
2020-02-14 15:58 ` Alan Stern
2020-02-15 0:09 ` Boqun Feng
2020-02-14 9:55 ` [RFC 0/3] tools/memory-model: Add litmus tests for atomic APIs Peter Zijlstra
2020-02-14 10:20 ` Paul E. McKenney
2020-02-14 15:27 ` Alan Stern
2020-02-14 23:39 ` Boqun Feng
2020-02-15 15:25 ` Paul E. McKenney
2020-02-16 5:43 ` Boqun Feng
2020-02-16 12:06 ` Paul E. McKenney
2020-02-16 16:16 ` Alan Stern
2020-02-17 1:27 ` Boqun Feng
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