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>,
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 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: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()
Date: Fri, 14 Feb 2020 12:01:32 +0800 [thread overview]
Message-ID: <20200214040132.91934-4-boqun.feng@gmail.com> (raw)
In-Reply-To: <20200214040132.91934-1-boqun.feng@gmail.com>
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)
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 4:01 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 ` Boqun Feng [this message]
2020-02-14 6:15 ` [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic() 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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