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-rw-r--r--mm/ksm.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 65ab5c7067d..43bc893470b 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1724,8 +1724,13 @@ static int ksm_memory_callback(struct notifier_block *self,
/*
* 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: