From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Jonathan Corbet <corbet@lwn.net>,
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>,
linux-doc@vger.kernel.org
Subject: [PATCH v2 2/4] Documentation: LKMM: Add litmus test for RCU GP guarantee where updater frees object
Date: Sun, 22 Mar 2020 21:57:33 -0400 [thread overview]
Message-ID: <20200323015735.236279-2-joel@joelfernandes.org> (raw)
In-Reply-To: <20200323015735.236279-1-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/RCU+sync+free.litmus | 42 +++++++++++++++++++
1 file changed, 42 insertions(+)
create mode 100644 Documentation/litmus-tests/rcu/RCU+sync+free.litmus
diff --git a/Documentation/litmus-tests/rcu/RCU+sync+free.litmus b/Documentation/litmus-tests/rcu/RCU+sync+free.litmus
new file mode 100644
index 0000000000000..4ee67e12f513a
--- /dev/null
+++ b/Documentation/litmus-tests/rcu/RCU+sync+free.litmus
@@ -0,0 +1,42 @@
+C RCU+sync+free
+
+(*
+ * Result: Never
+ *
+ * This litmus test demonstrates that an RCU reader can never see a write that
+ * follows a grace period, if it did not see writes that precede that grace
+ * period.
+ *
+ * This is a typical pattern of RCU usage, where the write before the grace
+ * period assigns a pointer, and the writes following the grace period destroy
+ * the object that the pointer used to point to.
+ *
+ * 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 = 1;
+int *y = &x;
+int z = 1;
+}
+
+P0(int *x, int *z, int **y)
+{
+ int *r0;
+ int r1;
+
+ rcu_read_lock();
+ r0 = rcu_dereference(*y);
+ r1 = READ_ONCE(*r0);
+ rcu_read_unlock();
+}
+
+P1(int *x, int *z, int **y)
+{
+ rcu_assign_pointer(*y, z);
+ synchronize_rcu();
+ WRITE_ONCE(*x, 0);
+}
+
+exists (0:r0=x /\ 0:r1=0)
--
2.25.1.696.g5e7596f4ac-goog
next prev parent reply other threads:[~2020-03-23 1:57 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-23 1:57 [PATCH v2 1/4] Documentation: LKMM: Move MP+onceassign+derefonce to new litmus-tests/rcu/ Joel Fernandes (Google)
2020-03-23 1:57 ` Joel Fernandes (Google) [this message]
2020-03-23 1:57 ` [PATCH v2 3/4] Documentation: LKMM: Add litmus test for RCU GP guarantee where reader stores Joel Fernandes (Google)
2020-03-23 1:57 ` [PATCH v2 4/4] MAINTAINERS: Update maintainers for new Documentaion/litmus-tests/ Joel Fernandes (Google)
2020-03-23 6:18 ` Boqun Feng
2020-03-23 8:59 ` Andrea Parri
2020-03-23 17:35 ` Paul E. McKenney
2020-05-09 3:43 ` [PATCH v2 1/4] Documentation: LKMM: Move MP+onceassign+derefonce to new litmus-tests/rcu/ Akira Yokosawa
2020-05-10 7:21 ` [PATCH 0/3] tools/memory-model, Documentation/litmus-test: Sort out location of litmus test and README Akira Yokosawa
2020-05-10 7:23 ` [PATCH 1/3] tools/memory-model: Fix reference to litmus test in recipes.txt Akira Yokosawa
2020-05-10 7:24 ` [PATCH 2/3] Revert "Documentation: LKMM: Move MP+onceassign+derefonce to new litmus-tests/rcu/" Akira Yokosawa
2020-05-10 7:28 ` [PATCH 3/3] Documentation/litmus-tests: Merge atomic's README into top-level one Akira Yokosawa
2020-05-10 12:57 ` [PATCH 0/3] tools/memory-model, Documentation/litmus-test: Sort out location of litmus test and README Andrea Parri
2020-05-11 17:33 ` Paul E. McKenney
2020-05-12 2:13 ` Joel Fernandes
2020-05-12 11:50 ` Akira Yokosawa
2020-05-12 12:19 ` Joel Fernandes
2020-05-12 14:19 ` Paul E. McKenney
2020-05-12 14:39 ` Akira Yokosawa
2020-05-12 15:40 ` Joel Fernandes
2020-05-12 13:44 ` Alan Stern
2020-05-12 15:07 ` [PATCH 4/3] docs: litmus-tests: Clarify about the RCU pre-initialization test Akira Yokosawa
2020-05-12 15:25 ` Alan Stern
2020-05-12 15:41 ` Joel Fernandes
2020-05-12 16:30 ` Paul E. McKenney
2020-05-12 21:33 ` [PATCH RESEND 0/4] tools/memory-model, Documentation/litmus-test: Sort out, location of litmus test and README Akira Yokosawa
2020-05-12 21:36 ` [PATCH RESEND 1/4] tools/memory-model: Fix reference to litmus test in recipes.txt Akira Yokosawa
2020-05-12 21:37 ` [PATCH RESEND 2/4] Revert "Documentation: LKMM: Move MP+onceassign+derefonce to new litmus-tests/rcu/" Akira Yokosawa
2020-05-12 21:39 ` [PATCH RESEND 3/4] Documentation/litmus-tests: Merge atomic's README into top-level one Akira Yokosawa
2020-05-14 0:46 ` Boqun Feng
2020-05-14 17:16 ` Paul E. McKenney
2020-05-14 22:03 ` Akira Yokosawa
2020-05-14 22:45 ` Paul E. McKenney
2020-05-15 15:01 ` Akira Yokosawa
2020-05-15 15:05 ` Paul E. McKenney
2020-05-16 17:02 ` Paul E. McKenney
2020-05-12 21:40 ` [PATCH RESEND 4/4] docs: litmus-tests: Clarify about the RCU pre-initialization test Akira Yokosawa
2020-05-12 21:43 ` [PATCH 4/3] " Joel Fernandes
2020-05-12 21:49 ` Akira Yokosawa
2020-05-12 22:52 ` Joel Fernandes
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