From: paulmck@kernel.org
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-team@fb.com, mingo@kernel.org
Cc: stern@rowland.harvard.edu, 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,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH lkmm tip/core/rcu 10/10] Documentation/litmus-tests/atomic: Add a test for smp_mb__after_atomic()
Date: Wed, 15 Apr 2020 11:49:45 -0700 [thread overview]
Message-ID: <20200415184945.16487-10-paulmck@kernel.org> (raw)
In-Reply-To: <20200415183343.GA12265@paulmck-ThinkPad-P72>
From: Boqun Feng <boqun.feng@gmail.com>
We already use a litmus test in atomic_t.txt to describe atomic RMW +
smp_mb__after_atomic() is stronger than acquire (both the read and the
write parts are ordered). So make it a litmus test in atomic-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.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/atomic_t.txt | 10 +++----
...b__after_atomic-is-stronger-than-acquire.litmus | 32 ++++++++++++++++++++++
Documentation/litmus-tests/atomic/README | 5 ++++
3 files changed, 42 insertions(+), 5 deletions(-)
create mode 100644 Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
index 67d1d99f..0f1fded 100644
--- a/Documentation/atomic_t.txt
+++ b/Documentation/atomic_t.txt
@@ -233,19 +233,19 @@ as well. Similarly, something like:
is an ACQUIRE pattern (though very much not typical), but again the barrier is
strictly stronger than ACQUIRE. As illustrated:
- C strong-acquire
+ C Atomic-RMW+mb__after_atomic-is-stronger-than-acquire
{
}
- 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();
@@ -253,14 +253,14 @@ strictly stronger than ACQUIRE. As illustrated:
}
exists
- (r0=1 /\ r1=0)
+ (0:r0=1 /\ 0:r1=0)
This should not happen; but a hypothetical atomic_inc_acquire() --
(void)atomic_fetch_inc_acquire() for instance -- would allow the outcome,
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/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus b/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
new file mode 100644
index 0000000..9a8e31a
--- /dev/null
+++ b/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
@@ -0,0 +1,32 @@
+C Atomic-RMW+mb__after_atomic-is-stronger-than-acquire
+
+(*
+ * Result: Never
+ *
+ * Test that an atomic RMW followed by a smp_mb__after_atomic() is
+ * stronger than a normal acquire: both the read and write parts of
+ * the RMW are ordered before the subsequential memory accesses.
+ *)
+
+{
+}
+
+P0(int *x, atomic_t *y)
+{
+ int r0;
+ int r1;
+
+ 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
+(0:r0=1 /\ 0:r1=0)
diff --git a/Documentation/litmus-tests/atomic/README b/Documentation/litmus-tests/atomic/README
index a1b7241..714cf93 100644
--- a/Documentation/litmus-tests/atomic/README
+++ b/Documentation/litmus-tests/atomic/README
@@ -7,5 +7,10 @@ tools/memory-model/README.
LITMUS TESTS
============
+Atomic-RMW+mb__after_atomic-is-stronger-than-acquire
+ Test that an atomic RMW followed by a smp_mb__after_atomic() is
+ stronger than a normal acquire: both the read and write parts of
+ the RMW are ordered before the subsequential memory accesses.
+
Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
Test that atomic_set() cannot break the atomicity of atomic RMWs.
--
2.9.5
prev parent reply other threads:[~2020-04-15 19:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 18:33 [PATCH kcsan 0/15] KCSAN updates for v5.8 Paul E. McKenney
2020-04-15 18:33 ` [PATCH v4 tip/core/rcu 01/15] kcsan: Add option to allow watcher interruptions paulmck
2020-04-15 18:33 ` [PATCH v4 tip/core/rcu 02/15] kcsan: Add option for verbose reporting paulmck
2020-04-15 18:33 ` [PATCH v4 tip/core/rcu 03/15] kcsan: Add current->state to implicitly atomic accesses paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 04/15] kcsan: Fix a typo in a comment paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 05/15] kcsan: Update Documentation/dev-tools/kcsan.rst paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 06/15] kcsan: Update API documentation in kcsan-checks.h paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 07/15] kcsan: Introduce report access_info and other_info paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 08/15] kcsan: Avoid blocking producers in prepare_report() paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 09/15] kcsan: Add support for scoped accesses paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 10/15] objtool, kcsan: Add explicit check functions to uaccess whitelist paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 11/15] kcsan: Introduce scoped ASSERT_EXCLUSIVE macros paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 12/15] kcsan: Move kcsan_{disable,enable}_current() to kcsan-checks.h paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 13/15] kcsan: Change data_race() to no longer require marking racing accesses paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 14/15] kcsan: Fix function matching in report paulmck
2020-04-15 18:34 ` [PATCH v4 tip/core/rcu 15/15] kcsan: Make reporting aware of KCSAN tests paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 01/10] tools/memory-model: Add recent references paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 02/10] tools/memory-model: Fix "conflict" definition paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 03/10] Documentation: LKMM: Move MP+onceassign+derefonce to new litmus-tests/rcu/ paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 04/10] Documentation: LKMM: Add litmus test for RCU GP guarantee where updater frees object paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 05/10] Documentation: LKMM: Add litmus test for RCU GP guarantee where reader stores paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 06/10] MAINTAINERS: Update maintainers for new Documentaion/litmus-tests/ paulmck
2020-04-15 21:39 ` Joe Perches
2020-04-16 0:17 ` Paul E. McKenney
2020-04-16 1:46 ` Joe Perches
2020-04-16 10:07 ` Paul E. McKenney
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 07/10] tools/memory-model: Add an exception for limitations on _unless() family paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 08/10] Documentation/litmus-tests: Introduce atomic directory paulmck
2020-04-15 18:49 ` [PATCH lkmm tip/core/rcu 09/10] Documentation/litmus-tests/atomic: Add a test for atomic_set() paulmck
2020-04-15 18:49 ` paulmck [this message]
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