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

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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>
This commit is contained in:
Paul E. McKenney 2015-09-20 22:02:17 -07:00
parent 6cf1008122
commit 1c97be677f
2 changed files with 5 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
include/linux/list.h
View file

@ -42,7 +42,7 @@ static inline void __list_add(struct list_head *new,
next->prev = new; next->prev = new;
new->next = next; new->next = next;
new->prev = prev; new->prev = prev;
prev->next = new; WRITE_ONCE(prev->next, new);
} }
#else #else
extern void __list_add(struct list_head *new, 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; n->next = first;
if (first) if (first)
first->pprev = &n->next; first->pprev = &n->next;
h->first = n; WRITE_ONCE(h->first, n);
n->pprev = &h->first; n->pprev = &h->first;
} }
@ -653,14 +653,14 @@ static inline void hlist_add_before(struct hlist_node *n,
n->pprev = next->pprev; n->pprev = next->pprev;
n->next = next; n->next = next;
next->pprev = &n->next; next->pprev = &n->next;
*(n->pprev) = n; WRITE_ONCE(*(n->pprev), n);
} }
static inline void hlist_add_behind(struct hlist_node *n, static inline void hlist_add_behind(struct hlist_node *n,
struct hlist_node *prev) struct hlist_node *prev)
{ {
n->next = prev->next; n->next = prev->next;
prev->next = n; WRITE_ONCE(prev->next, n);
n->pprev = &prev->next; n->pprev = &prev->next;
if (n->next) if (n->next)

2
lib/list_debug.c
View file

@ -37,7 +37,7 @@ void __list_add(struct list_head *new,
next->prev = new; next->prev = new;
new->next = next; new->next = next;
new->prev = prev; new->prev = prev;
prev->next = new; WRITE_ONCE(prev->next, new);
} }
EXPORT_SYMBOL(__list_add); EXPORT_SYMBOL(__list_add);