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,
"Joel Fernandes (Google)" <joel@joelfernandes.org>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 04/14] Documentation: LKMM: Add litmus test for RCU GP guarantee where reader stores
Date: Mon, 22 Jun 2020 17:52:21 -0700 [thread overview]
Message-ID: <20200623005231.27712-4-paulmck@kernel.org> (raw)
In-Reply-To: <20200623005152.GA27459@paulmck-ThinkPad-P72>
From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
This adds an example for the important RCU grace period guarantee, which
shows an RCU reader can never span a grace period.
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/litmus-tests/README | 11 +++++++
.../litmus-tests/rcu/RCU+sync+read.litmus | 37 ++++++++++++++++++++++
2 files changed, 48 insertions(+)
create mode 100644 Documentation/litmus-tests/README
create mode 100644 Documentation/litmus-tests/rcu/RCU+sync+read.litmus
diff --git a/Documentation/litmus-tests/README b/Documentation/litmus-tests/README
new file mode 100644
index 0000000..c4307ea
--- /dev/null
+++ b/Documentation/litmus-tests/README
@@ -0,0 +1,11 @@
+============
+LITMUS TESTS
+============
+
+RCU (/rcu directory)
+--------------------
+
+RCU+sync+read.litmus
+RCU+sync+free.litmus
+ Both the above litmus tests demonstrate the RCU grace period guarantee
+ that an RCU read-side critical section can never span a grace period.
diff --git a/Documentation/litmus-tests/rcu/RCU+sync+read.litmus b/Documentation/litmus-tests/rcu/RCU+sync+read.litmus
new file mode 100644
index 0000000..f341767
--- /dev/null
+++ b/Documentation/litmus-tests/rcu/RCU+sync+read.litmus
@@ -0,0 +1,37 @@
+C RCU+sync+read
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that after a grace period, an RCU updater always
+ * sees all stores done in prior RCU read-side critical sections. Such
+ * read-side critical sections would have ended before the grace period ended.
+ *
+ * This is one implication of the RCU grace-period guarantee, which says (among
+ * other things) that an RCU read-side critical section cannot span a grace period.
+ *)
+
+{
+int x = 0;
+int y = 0;
+}
+
+P0(int *x, int *y)
+{
+ rcu_read_lock();
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ rcu_read_unlock();
+}
+
+P1(int *x, int *y)
+{
+ int r0;
+ int r1;
+
+ r0 = READ_ONCE(*x);
+ synchronize_rcu();
+ r1 = READ_ONCE(*y);
+}
+
+exists (1:r0=1 /\ 1:r1=0)
--
2.9.5
next prev parent reply other threads:[~2020-06-23 0:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 0:51 [PATCH memory-model 0/14] LKMM updates for v5.9 Paul E. McKenney
2020-06-23 0:52 ` [PATCH tip/core/rcu 01/14] tools/memory-model: Add recent references paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 02/14] tools/memory-model: Fix "conflict" definition paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 03/14] Documentation: LKMM: Add litmus test for RCU GP guarantee where updater frees object paulmck
2020-06-23 0:52 ` paulmck [this message]
2020-06-23 0:52 ` [PATCH tip/core/rcu 05/14] MAINTAINERS: Update maintainers for new Documentation/litmus-tests paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 06/14] tools/memory-model: Add an exception for limitations on _unless() family paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 07/14] Documentation/litmus-tests: Introduce atomic directory paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 08/14] Documentation/litmus-tests/atomic: Add a test for atomic_set() paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 09/14] Documentation/litmus-tests/atomic: Add a test for smp_mb__after_atomic() paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 10/14] tools/memory-model: Fix reference to litmus test in recipes.txt paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 11/14] Documentation/litmus-tests: Merge atomic's README into top-level one paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 12/14] Documentation/litmus-tests: Cite an RCU litmus test paulmck
2020-06-23 0:52 ` [PATCH tip/core/rcu 13/14] tools/memory-model/README: Expand dependency of klitmus7 paulmck
2020-06-23 14:37 ` Akira Yokosawa
2020-06-23 15:54 ` Paul E. McKenney
2020-06-23 22:06 ` [PATCH 1/2] tools/memory-model/README: Mention herdtools7 7.56 in compatibility table Akira Yokosawa
2020-06-23 22:09 ` [PATCH 2/2] Documentation/litmus-tests: Add note on herd7 7.56 in atomic litmus test Akira Yokosawa
2020-06-23 23:24 ` Andrea Parri
2020-06-24 4:05 ` Paul E. McKenney
2020-06-23 22:57 ` [PATCH 1/2] tools/memory-model/README: Mention herdtools7 7.56 in compatibility table Andrea Parri
2020-06-23 0:52 ` [PATCH tip/core/rcu 14/14] docs: fix references for DMA*.txt files paulmck
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