rcutorture: Add a lock_busted to test the test

This commit adds a maximally broken locking primitive in which
lock acquisition and release are both no-ops.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 32 insertions, 1 deletions

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index d69d20d9c9db..f26b1a18e34e 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -112,6 +112,37 @@ static struct lock_torture_ops *cur_ops;
  * Definitions for lock torture testing.
  */
 
+static int torture_lock_busted_write_lock(void)
+{
+        return 0;  /* BUGGY, do not use in real life!!! */
+}
+
+static void torture_lock_busted_write_delay(struct torture_random_state *trsp)
+{
+        const unsigned long longdelay_us = 100;
+
+        /* We want a long delay occasionally to force massive contention.  */
+        if (!(torture_random(trsp) %
+              (nrealwriters_stress * 2000 * longdelay_us)))
+                mdelay(longdelay_us);
+#ifdef CONFIG_PREEMPT
+        if (!(torture_random(trsp) % (nrealwriters_stress * 20000)))
+                preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_lock_busted_write_unlock(void)
+{
+          /* BUGGY, do not use in real life!!! */
+}
+
+static struct lock_torture_ops lock_busted_ops = {
+        .writelock      = torture_lock_busted_write_lock,
+        .write_delay    = torture_lock_busted_write_delay,
+        .writeunlock    = torture_lock_busted_write_unlock,
+        .name           = "lock_busted"
+};
+
 static DEFINE_SPINLOCK(torture_spinlock);
 
 static int torture_spin_lock_write_lock(void) __acquires(torture_spinlock)
@@ -320,7 +351,7 @@ static int __init lock_torture_init(void)
         int i;
         int firsterr = 0;
         static struct lock_torture_ops *torture_ops[] = {
-                &spin_lock_ops, &spin_lock_irq_ops,
+                &lock_busted_ops, &spin_lock_ops, &spin_lock_irq_ops,
         };
 
         torture_init_begin(torture_type, verbose, &locktorture_runnable);