summaryrefslogtreecommitdiff
path: root/Documentation/litmus-tests
diff options
context:
space:
mode:
authorJoel Fernandes (Google) <joel@joelfernandes.org>2020-03-23 04:57:34 +0300
committerPaul E. McKenney <paulmck@kernel.org>2020-06-29 22:05:18 +0300
commita591890c4e91f37ce858a3090b16e0eef2511575 (patch)
tree52a178c6611610e12262984a461f4120b5f0c7ae /Documentation/litmus-tests
parentbe4a37973cb078fc64d541f396b7d4d80e45fbe2 (diff)
downloadlinux-a591890c4e91f37ce858a3090b16e0eef2511575.tar.xz
Documentation: LKMM: Add litmus test for RCU GP guarantee where reader stores
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>
Diffstat (limited to 'Documentation/litmus-tests')
-rw-r--r--Documentation/litmus-tests/README11
-rw-r--r--Documentation/litmus-tests/rcu/RCU+sync+read.litmus37
2 files changed, 48 insertions, 0 deletions
diff --git a/Documentation/litmus-tests/README b/Documentation/litmus-tests/README
new file mode 100644
index 000000000000..c4307ea9f996
--- /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 000000000000..f34176720231
--- /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)