md: delay notification of 'active_idle' to the recovery thread

sysfs_notify might sleep, so do not call it from md_safemode_timeout.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index c2ff77c..0f1b830 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3483,7 +3483,7 @@
 	if (!atomic_read(&mddev->writes_pending)) {
 		mddev->safemode = 1;
 		if (mddev->external)
-			sysfs_notify(&mddev->kobj, NULL, "array_state");
+			set_bit(MD_NOTIFY_ARRAY_STATE, &mddev->flags);
 	}
 	md_wakeup_thread(mddev->thread);
 }
@@ -6051,6 +6051,9 @@
 	if (mddev->bitmap)
 		bitmap_daemon_work(mddev->bitmap);
 
+	if (test_and_clear_bit(MD_NOTIFY_ARRAY_STATE, &mddev->flags))
+		sysfs_notify(&mddev->kobj, NULL, "array_state");
+
 	if (mddev->ro)
 		return;