From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Akira Yokosawa <akiyks@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <parri.andrea@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
linux-arch@vger.kernel.org, Luc Maranget <luc.maranget@inria.fr>,
Nicholas Piggin <npiggin@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>
Subject: [PATCH 2/3] LKMM: Add litmus test for RCU GP guarantee where reader stores
Date: Fri, 20 Mar 2020 02:55:51 -0400 [thread overview]
Message-ID: <20200320065552.253696-2-joel@joelfernandes.org> (raw)
In-Reply-To: <20200320065552.253696-1-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.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
.../litmus-tests/RCU+sync+read.litmus | 37 +++++++++++++++++++
1 file changed, 37 insertions(+)
create mode 100644 tools/memory-model/litmus-tests/RCU+sync+read.litmus
diff --git a/tools/memory-model/litmus-tests/RCU+sync+read.litmus b/tools/memory-model/litmus-tests/RCU+sync+read.litmus
new file mode 100644
index 0000000000000..73557772e2a32
--- /dev/null
+++ b/tools/memory-model/litmus-tests/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 guarantee also implies, an RCU reader can never span a grace period and
+ * is an important RCU grace period memory ordering guarantee.
+ *)
+
+{
+x = 0;
+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)
--
2.25.1.696.g5e7596f4ac-goog
next prev parent reply other threads:[~2020-03-20 6:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 6:55 [PATCH 1/3] LKMM: Add litmus test for RCU GP guarantee where updater frees object Joel Fernandes (Google)
2020-03-20 6:55 ` Joel Fernandes (Google) [this message]
2020-03-20 15:03 ` [PATCH 2/3] LKMM: Add litmus test for RCU GP guarantee where reader stores Alan Stern
2020-03-20 16:59 ` Joel Fernandes
2020-03-20 20:56 ` Alan Stern
2020-03-20 21:44 ` Joel Fernandes
2020-03-21 2:05 ` Boqun Feng
2020-03-23 1:31 ` Joel Fernandes
2020-03-20 6:55 ` [PATCH 3/3] LKMM: Rename MP+onceassign+derefonce for better clarity Joel Fernandes (Google)
2020-03-20 10:26 ` [PATCH 1/3] LKMM: Add litmus test for RCU GP guarantee where updater frees object Andrea Parri
2020-03-20 15:07 ` Alan Stern
2020-03-20 16:54 ` Joel Fernandes
2020-03-20 10:44 ` Andrea Parri
2020-03-20 14:59 ` Alan Stern
2020-03-20 20:15 ` Joel Fernandes
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