md: md_unregister_thread should cope with being passed NULL

Mostly md_unregister_thread is only called when we know that the
thread is NULL, but sometimes we need to check first.  It is safer
to put the check inside md_unregister_thread itself.

Signed-off-by: NeilBrown <neilb@suse.de>

2 files changed, 3 insertions, 2 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 117ea5fde568..f30f09cb08e8 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5382,6 +5382,8 @@ mdk_thread_t *md_register_thread(void (*run) (mddev_t *), mddev_t *mddev,
 
 void md_unregister_thread(mdk_thread_t *thread)
 {
+        if (!thread)
+                return;
         dprintk("interrupting MD-thread pid %d\n", task_pid_nr(thread->tsk));
 
         kthread_stop(thread->tsk);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d019a85547b4..81789fa7a023 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4463,8 +4463,7 @@ static int run(mddev_t *mddev)
 
         return 0;
 abort:
-        if (mddev->thread)
-                md_unregister_thread(mddev->thread);
+        md_unregister_thread(mddev->thread);
         mddev->thread = NULL;
         if (conf) {
                 shrink_stripes(conf);