[PATCH] rcu: add sched torture type to rcutorture

Implement torture testing for the "sched" variant of RCU, which uses
preempt_disable, preempt_enable, and synchronize_sched.
Signed-off-by: NJosh Triplett <josh@freedesktop.org>
Acked-by: NPaul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation/RCU/torture.txt

@@ -56,8 +56,9 @@ test_no_idle_hz	Whether or not to test the ability of RCU to operate in
 torture_type	The type of RCU to test: "rcu" for the rcu_read_lock() API,
 		"rcu_sync" for rcu_read_lock() with synchronous reclamation,
 		"rcu_bh" for the rcu_read_lock_bh() API, "rcu_bh_sync" for
-		rcu_read_lock_bh() with synchronous reclamation, and "srcu"
-		for the "srcu_read_lock()" API.
+		rcu_read_lock_bh() with synchronous reclamation, "srcu" for
+		the "srcu_read_lock()" API, and "sched" for the use of
+		preempt_disable() together with synchronize_sched().
 
 verbose		Enable debug printk()s.  Default is disabled.
 

kernel/rcutorture.c

@@ -464,9 +464,47 @@ static struct rcu_torture_ops srcu_ops = {
 	.name = "srcu"
 };
 
+/*
+ * Definitions for sched torture testing.
+ */
+
+static int sched_torture_read_lock(void)
+{
+	preempt_disable();
+	return 0;
+}
+
+static void sched_torture_read_unlock(int idx)
+{
+	preempt_enable();
+}
+
+static int sched_torture_completed(void)
+{
+	return 0;
+}
+
+static void sched_torture_synchronize(void)
+{
+	synchronize_sched();
+}
+
+static struct rcu_torture_ops sched_ops = {
+	.init = rcu_sync_torture_init,
+	.cleanup = NULL,
+	.readlock = sched_torture_read_lock,
+	.readdelay = rcu_read_delay,  /* just reuse rcu's version. */
+	.readunlock = sched_torture_read_unlock,
+	.completed = sched_torture_completed,
+	.deferredfree = rcu_sync_torture_deferred_free,
+	.sync = sched_torture_synchronize,
+	.stats = NULL,
+	.name = "sched"
+};
+
 static struct rcu_torture_ops *torture_ops[] =
 	{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops, &srcu_ops,
-	  NULL };
+	  &sched_ops, NULL };
 
 /*
  * RCU torture writer kthread.  Repeatedly substitutes a new structure