list: Use WRITE_ONCE() when adding to lists and hlists

Code that does lockless emptiness testing of non-RCU lists is relying
on the list-addition code to write the list head's ->next pointer
atomically.  This commit therefore adds WRITE_ONCE() to list-addition
pointer stores that could affect the head's ->next pointer.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/list_debug.c b/lib/list_debug.c
index c24c2f7e296f..3859bf63561c 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -37,7 +37,7 @@ void __list_add(struct list_head *new,
         next->prev = new;
         new->next = next;
         new->prev = prev;
-        prev->next = new;
+        WRITE_ONCE(prev->next, new);
 }
 EXPORT_SYMBOL(__list_add);