From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Alan Stern <stern@rowland.harvard.edu>,
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 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()
Date: Fri, 14 Feb 2020 14:15:37 +0800 [thread overview]
Message-ID: <20200214061537.GA20408@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> (raw)
In-Reply-To: <20200214040132.91934-4-boqun.feng@gmail.com>
On Fri, Feb 14, 2020 at 12:01:32PM +0800, Boqun Feng wrote:
> We already use a litmus test in atomic_t.txt to describe atomic RMW +
> smp_mb__after_atomic() is "strong acquire" (both the read and the write
> part is ordered). So make it a litmus test in memory-model litmus-tests
> directory, so that people can access the litmus easily.
>
> Additionally, change the processor numbers "P1, P2" to "P0, P1" in
> atomic_t.txt for the consistency with the processor numbers in the
> litmus test, which herd can handle.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> ---
> Documentation/atomic_t.txt | 6 ++--
> ...+mb__after_atomic-is-strong-acquire.litmus | 29 +++++++++++++++++++
> tools/memory-model/litmus-tests/README | 5 ++++
> 3 files changed, 37 insertions(+), 3 deletions(-)
> create mode 100644 tools/memory-model/litmus-tests/Atomic-RMW+mb__after_atomic-is-strong-acquire.litmus
>
> diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
> index ceb85ada378e..e3ad4e4cd9ed 100644
> --- a/Documentation/atomic_t.txt
> +++ b/Documentation/atomic_t.txt
> @@ -238,14 +238,14 @@ strictly stronger than ACQUIRE. As illustrated:
> {
> }
>
> - P1(int *x, atomic_t *y)
> + P0(int *x, atomic_t *y)
> {
> r0 = READ_ONCE(*x);
> smp_rmb();
> r1 = atomic_read(y);
> }
>
> - P2(int *x, atomic_t *y)
> + P1(int *x, atomic_t *y)
> {
> atomic_inc(y);
> smp_mb__after_atomic();
> @@ -260,7 +260,7 @@ This should not happen; but a hypothetical atomic_inc_acquire() --
> because it would not order the W part of the RMW against the following
> WRITE_ONCE. Thus:
>
> - P1 P2
> + P0 P1
>
> t = LL.acq *y (0)
> t++;
> diff --git a/tools/memory-model/litmus-tests/Atomic-RMW+mb__after_atomic-is-strong-acquire.litmus b/tools/memory-model/litmus-tests/Atomic-RMW+mb__after_atomic-is-strong-acquire.litmus
> new file mode 100644
> index 000000000000..e7216cf9d92a
> --- /dev/null
> +++ b/tools/memory-model/litmus-tests/Atomic-RMW+mb__after_atomic-is-strong-acquire.litmus
> @@ -0,0 +1,29 @@
> +C Atomic-RMW+mb__after_atomic-is-strong-acquire
> +
> +(*
> + * Result: Never
> + *
> + * Test of an atomic RMW followed by a smp_mb__after_atomic() is
> + * "strong-acquire": both the read and write part of the RMW is ordered before
> + * the subsequential memory accesses.
> + *)
> +
> +{
> +}
> +
> +P0(int *x, atomic_t *y)
> +{
> + r0 = READ_ONCE(*x);
> + smp_rmb();
> + r1 = atomic_read(y);
> +}
> +
> +P1(int *x, atomic_t *y)
> +{
> + atomic_inc(y);
> + smp_mb__after_atomic();
> + WRITE_ONCE(*x, 1);
> +}
> +
> +exists
> +(r0=1 /\ r1=0)
Hmm.. this should be "(0:r0=1 /\ 0:r1=0)", I will fix this in next
verison.
Regards,
Boqun
> diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README
> index 81eeacebd160..774e10058c72 100644
> --- a/tools/memory-model/litmus-tests/README
> +++ b/tools/memory-model/litmus-tests/README
> @@ -2,6 +2,11 @@
> LITMUS TESTS
> ============
>
> +Atomic-RMW+mb__after_atomic-is-strong-acquire
> + Test of an atomic RMW followed by a smp_mb__after_atomic() is
> + "strong-acquire": both the read and write part of the RMW is ordered
> + before the subsequential memory accesses.
> +
> Atomic-set-observable-to-RMW.litmus
> Test of the result of atomic_set() must be observable to atomic RMWs.
>
> --
> 2.25.0
>
next prev parent reply other threads:[~2020-02-14 6:15 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
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 [this message]
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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