Commit-ID: 1c97be677f72b3c338312aecd36d8fff20322f32
Gitweb: http://git.kernel.org/tip/1c97be677f72b3c338312aecd36d8fff20322f32
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Sun, 20 Sep 2015 22:02:17 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 23 Nov 2015 10:37:35 -0800
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@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
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 993395a..d7e31fe 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 c24c2f7..3859bf6 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);
--
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