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/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 9f2549a..c200b9a 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -128,6 +128,7 @@
 #define MD_CHANGE_DEVS	0	/* Some device status has changed */
 #define MD_CHANGE_CLEAN 1	/* transition to or from 'clean' */
 #define MD_CHANGE_PENDING 2	/* superblock update in progress */
+#define MD_NOTIFY_ARRAY_STATE 3	/* atomic context wants to notify userspace */
 
 	int				ro;