[PATCH memory-model 1/3] Documentation/litmus-tests: Add locking tests to README

[Paul E. McKenney]

This commit documents the litmus tests in the "locking" directory.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Jade Alglave <j.alglave@xxxxxxxxx>
Cc: Luc Maranget <luc.maranget@xxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Akira Yokosawa <akiyks@xxxxxxxxx>
Cc: Daniel Lustig <dlustig@xxxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: <linux-arch@xxxxxxxxxxxxxxx>
Cc: <linux-doc@xxxxxxxxxxxxxxx>
---
 Documentation/litmus-tests/README | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/litmus-tests/README b/Documentation/litmus-tests/README
index 658d37860d397..5c8915e6fb684 100644
--- a/Documentation/litmus-tests/README
+++ b/Documentation/litmus-tests/README
@@ -22,6 +22,35 @@ Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
     NOTE: Require herd7 7.56 or later which supports "(void)expr".
 
 
+locking (/locking directory)
+----------------------------
+
+DCL-broken.litmus
+	Demonstrates that double-checked locking needs more than just
+	the obvious lock acquisitions and releases.
+
+DCL-fixed.litmus
+	Demonstrates corrected double-checked locking that uses
+	smp_store_release() and smp_load_acquire() in addition to the
+	obvious lock acquisitions and releases.
+
+RM-broken.litmus
+	Demonstrates problems with "roach motel" locking, where code is
+	freely moved into lock-based critical sections.  This example also
+	shows how to use the "filter" clause to discard executions that
+	would be excluded by other code not modeled in the litmus test.
+	Note also that this "roach motel" optimization is emulated by
+	physically moving P1()'s two reads from x under the lock.
+
+	What is a roach motel?	This is from an old advertisement for
+	a cockroach trap, much later featured in one of the "Men in
+	Black" movies.	"The roaches check in.	They don't check out."
+
+RM-fixed.litmus
+	The counterpart to RM-broken.litmus, showing P0()'s two loads from
+	x safely outside of the critical section.
+
+
 RCU (/rcu directory)
 --------------------
 
-- 
2.40.1