From 1c97be677f72b3c338312aecd36d8fff20322f32 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 20 Sep 2015 22:02:17 -0700 Subject: [PATCH] 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 Signed-off-by: Paul E. McKenney --- include/linux/list.h | 8 ++++---- lib/list_debug.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index 993395a2e55c..d7e31fe398b3 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -42,7 +42,7 @@ static inline void __list_add(struct list_head *new, next->prev = new; new->next = next; new->prev = prev; - prev->next = new; + WRITE_ONCE(prev->next, new); } #else extern void __list_add(struct list_head *new, @@ -642,7 +642,7 @@ static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) n->next = first; if (first) first->pprev = &n->next; - h->first = n; + WRITE_ONCE(h->first, n); n->pprev = &h->first; } @@ -653,14 +653,14 @@ static inline void hlist_add_before(struct hlist_node *n, n->pprev = next->pprev; n->next = next; next->pprev = &n->next; - *(n->pprev) = n; + WRITE_ONCE(*(n->pprev), n); } static inline void hlist_add_behind(struct hlist_node *n, struct hlist_node *prev) { n->next = prev->next; - prev->next = n; + WRITE_ONCE(prev->next, n); n->pprev = &prev->next; if (n->next) 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); -- 2.20.1