locktorture: Support rwlocks

Add a "rw_lock" torture test to stress kernel rwlocks and their irq
variant. Reader critical regions are 5x longer than writers. As such
a similar ratio of lock acquisitions is seen in the statistics. In the
case of massive contention, both hold the lock for 1/10 of a second.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
index be71501..619f2bb 100644
--- a/Documentation/locking/locktorture.txt
+++ b/Documentation/locking/locktorture.txt
@@ -45,6 +45,11 @@
 		     o "spin_lock_irq": spin_lock_irq() and spin_unlock_irq()
 					pairs.
 
+		     o "rw_lock": read/write lock() and unlock() rwlock pairs.
+
+		     o "rw_lock_irq": read/write lock_irq() and unlock_irq()
+				      rwlock pairs.
+
 		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
 
 		     o "rwsem_lock": read/write down() and up() semaphore pairs.