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>
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 @@
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 @@
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 @@
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)