diff --git a/mm/ksm.c b/mm/ksm.c
index 65ab5c7..43bc893 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1724,8 +1724,13 @@
 		/*
 		 * Keep it very simple for now: just lock out ksmd and
 		 * MADV_UNMERGEABLE while any memory is going offline.
+		 * mutex_lock_nested() is necessary because lockdep was alarmed
+		 * that here we take ksm_thread_mutex inside notifier chain
+		 * mutex, and later take notifier chain mutex inside
+		 * ksm_thread_mutex to unlock it.   But that's safe because both
+		 * are inside mem_hotplug_mutex.
 		 */
-		mutex_lock(&ksm_thread_mutex);
+		mutex_lock_nested(&ksm_thread_mutex, SINGLE_DEPTH_NESTING);
 		break;
 
 	case MEM_OFFLINE: