rcutorture: Abstract torture_shutdown_notify()

Because handling the race between rmmod and system shutdown is not
specific to RCU, this commit abstracts torture_shutdown_notify(),
placing this code into kernel/torture.c.  This change also allows
fullstop_mutex to be private to kernel/torture.c.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

include/linux/torture.h

@@ -46,8 +46,6 @@
 #define FULLSTOP_SHUTDOWN 1	/* System shutdown with rcutorture running. */
 #define FULLSTOP_RMMOD    2	/* Normal rmmod of rcutorture. */
 extern int fullstop;
-/* Protect fullstop transitions and spawning of kthreads.  */
-extern struct mutex fullstop_mutex;
 
 #define TORTURE_FLAG "-torture:"
 #define TOROUT_STRING(s) \

kernel/rcu/rcutorture.c

@@ -189,23 +189,6 @@ static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
 /* Forward reference. */
 static void rcu_torture_cleanup(void);
 
-/*
- * Detect and respond to a system shutdown.
- */
-static int
-rcutorture_shutdown_notify(struct notifier_block *unused1,
-			   unsigned long unused2, void *unused3)
-{
-	mutex_lock(&fullstop_mutex);
-	if (fullstop == FULLSTOP_DONTSTOP)
-		fullstop = FULLSTOP_SHUTDOWN;
-	else
-		pr_warn(/* but going down anyway, so... */
-		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
-	mutex_unlock(&fullstop_mutex);
-	return NOTIFY_DONE;
-}
-
 /*
  * Allocate an element from the rcu_tortures pool.
  */
@@ -1098,10 +1081,6 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 onoff_interval, onoff_holdoff);
 }
 
-static struct notifier_block rcutorture_shutdown_nb = {
-	.notifier_call = rcutorture_shutdown_notify,
-};
-
 static void rcutorture_booster_cleanup(int cpu)
 {
 	struct task_struct *t;
@@ -1428,7 +1407,6 @@ rcu_torture_cleanup(void)
 			cur_ops->cb_barrier();
 		return;
 	}
-	unregister_reboot_notifier(&rcutorture_shutdown_nb);
 
 	rcu_torture_barrier_cleanup();
 	rcu_torture_stall_cleanup();
@@ -1774,7 +1752,6 @@ rcu_torture_init(void)
 		firsterr = i;
 		goto unwind;
 	}
-	register_reboot_notifier(&rcutorture_shutdown_nb);
 	i = rcu_torture_stall_init();
 	if (i != 0) {
 		firsterr = i;

kernel/torture.c

@@ -54,8 +54,7 @@ static bool verbose;
 
 int fullstop = FULLSTOP_RMMOD;
 EXPORT_SYMBOL_GPL(fullstop);
-DEFINE_MUTEX(fullstop_mutex);
-EXPORT_SYMBOL_GPL(fullstop_mutex);
+static DEFINE_MUTEX(fullstop_mutex);
 
 #ifdef CONFIG_HOTPLUG_CPU
 
@@ -422,14 +421,32 @@ EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
 void torture_shutdown_absorb(const char *title)
 {
 	while (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
-		pr_notice(
-		       "torture thread %s parking due to system shutdown\n",
-		       title);
+		pr_notice("torture thread %s parking due to system shutdown\n",
+			  title);
 		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
 	}
 }
 EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
 
+/*
+ * Detect and respond to a system shutdown.
+ */
+static int torture_shutdown_notify(struct notifier_block *unused1,
+				   unsigned long unused2, void *unused3)
+{
+	mutex_lock(&fullstop_mutex);
+	if (fullstop == FULLSTOP_DONTSTOP)
+		fullstop = FULLSTOP_SHUTDOWN;
+	else
+		pr_warn("Concurrent rmmod and shutdown illegal!\n");
+	mutex_unlock(&fullstop_mutex);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block torture_shutdown_nb = {
+	.notifier_call = torture_shutdown_notify,
+};
+
 /*
  * Initialize torture module.  Please note that this is -not- invoked via
  * the usual module_init() mechanism, but rather by an explicit call from
@@ -451,6 +468,7 @@ EXPORT_SYMBOL_GPL(torture_init_begin);
 void __init torture_init_end(void)
 {
 	mutex_unlock(&fullstop_mutex);
+	register_reboot_notifier(&torture_shutdown_nb);
 }
 EXPORT_SYMBOL_GPL(torture_init_end);
 
@@ -474,6 +492,7 @@ bool torture_cleanup(void)
 	}
 	fullstop = FULLSTOP_RMMOD;
 	mutex_unlock(&fullstop_mutex);
+	unregister_reboot_notifier(&torture_shutdown_nb);
 	torture_shuffle_cleanup();
 	torture_onoff_cleanup();
 	return false;