rcutorture: Apply ACCESS_ONCE() to racy fullstop accesses

Because the fullstop variable can be accessed while it is being updated,
this commit avoids any resulting compiler mischief through use of
ACCESS_ONCE() for non-initialization accesses to this shared variable.

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

diff --git a/kernel/torture.c b/kernel/torture.c
index b30c2ee78580125731855491d75b80499980b880..1bafd02d1eedd9cf268aabb54fbae86355894bb9 100644 (file)
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -439,9 +439,9 @@ static int torture_shutdown_notify(struct notifier_block *unused1,
                                   unsigned long unused2, void *unused3)
 {
        mutex_lock(&fullstop_mutex);
-       if (fullstop == FULLSTOP_DONTSTOP) {
+       if (ACCESS_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
                VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
-               fullstop = FULLSTOP_SHUTDOWN;
+               ACCESS_ONCE(fullstop) = FULLSTOP_SHUTDOWN;
        } else {
                pr_warn("Concurrent rmmod and shutdown illegal!\n");
        }
@@ -575,13 +575,13 @@ EXPORT_SYMBOL_GPL(torture_init_end);
 bool torture_cleanup(void)
 {
        mutex_lock(&fullstop_mutex);
-       if (fullstop == FULLSTOP_SHUTDOWN) {
+       if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
                pr_warn("Concurrent rmmod and shutdown illegal!\n");
                mutex_unlock(&fullstop_mutex);
                schedule_timeout_uninterruptible(10);
                return true;
        }
-       fullstop = FULLSTOP_RMMOD;
+       ACCESS_ONCE(fullstop) = FULLSTOP_RMMOD;
        mutex_unlock(&fullstop_mutex);
        unregister_reboot_notifier(&torture_shutdown_nb);
        torture_shuffle_cleanup();
@@ -605,6 +605,6 @@ EXPORT_SYMBOL_GPL(torture_must_stop);
  */
 bool torture_must_stop_irq(void)
 {
-       return fullstop != FULLSTOP_DONTSTOP;
+       return ACCESS_ONCE(fullstop) != FULLSTOP_DONTSTOP;
 }
 EXPORT_SYMBOL_GPL(torture_must_stop_irq);