rcutorture: Add an rcu_busted to test the test

This commit adds a deliberately buggy RCU implementation into rcutorture
to allow easy checking that rcutorture correctly flags buggy RCU
implementations.

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

1 files changed, 43 insertions, 1 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 40792e76a116..da6c38d909f1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -372,6 +372,48 @@ static struct rcu_torture_ops rcu_bh_ops = {
 };
 
 /*
+ * Don't even think about trying any of these in real life!!!
+ * The names includes "busted", and they really means it!
+ * The only purpose of these functions is to provide a buggy RCU
+ * implementation to make sure that rcutorture correctly emits
+ * buggy-RCU error messages.
+ */
+static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
+{
+        /* This is a deliberate bug for testing purposes only! */
+        rcu_torture_cb(&p->rtort_rcu);
+}
+
+static void synchronize_rcu_busted(void)
+{
+        /* This is a deliberate bug for testing purposes only! */
+}
+
+static void
+call_rcu_busted(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+        /* This is a deliberate bug for testing purposes only! */
+        func(head);
+}
+
+static struct rcu_torture_ops rcu_busted_ops = {
+        .init           = rcu_sync_torture_init,
+        .readlock       = rcu_torture_read_lock,
+        .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+        .readunlock     = rcu_torture_read_unlock,
+        .completed      = rcu_no_completed,
+        .deferred_free  = rcu_busted_torture_deferred_free,
+        .sync           = synchronize_rcu_busted,
+        .exp_sync       = synchronize_rcu_busted,
+        .call           = call_rcu_busted,
+        .cb_barrier     = NULL,
+        .fqs            = NULL,
+        .stats          = NULL,
+        .irq_capable    = 1,
+        .name           = "rcu_busted"
+};
+
+/*
  * Definitions for srcu torture testing.
  */
 
@@ -1371,7 +1413,7 @@ rcu_torture_init(void)
         int cpu;
         int firsterr = 0;
         static struct rcu_torture_ops *torture_ops[] = {
-                &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
+                &rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops,
         };
 
         torture_init_begin(torture_type, verbose, &rcutorture_runnable);