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authorLinus Torvalds <torvalds@linux-foundation.org>2008-04-20 21:59:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-21 08:23:35 -0700
commitcc216c5d429892872f70f76975e243aef7ad9db1 (patch)
tree6455048df83fb61c870367f7a88e701e44ebdd24
parent3925e6fc1f774048404fdd910b0345b06c699eb4 (diff)
Fix RCU list iterator use of 'rcu_dereference()'
The RCU iterators used 'rcu_dereference()' on an already-fetched RCU pointer value, which defeats the whole point of the exercise. When we dereference a pointer protected by RCU, we need to make sure that we only fetch the value _once_, because if the compiler ends up re-loading it due to register pressure, the newly reloaded value could be different from the previously fetched one, and you get inconsistent results. Cleaned-up, fixed, and the pointless list_for_each_safe_rcu #define deleted by Paul Kenney. Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/list.h48
1 files changed, 15 insertions, 33 deletions
diff --git a/include/linux/list.h b/include/linux/list.h
index 75ce2cb4ff6..dac16f99c70 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -631,31 +631,14 @@ static inline void list_splice_init_rcu(struct list_head *list,
* as long as the traversal is guarded by rcu_read_lock().
*/
#define list_for_each_rcu(pos, head) \
- for (pos = (head)->next; \
- prefetch(rcu_dereference(pos)->next), pos != (head); \
- pos = pos->next)
+ for (pos = rcu_dereference((head)->next); \
+ prefetch(pos->next), pos != (head); \
+ pos = rcu_dereference(pos->next))
#define __list_for_each_rcu(pos, head) \
- for (pos = (head)->next; \
- rcu_dereference(pos) != (head); \
- pos = pos->next)
-
-/**
- * list_for_each_safe_rcu
- * @pos: the &struct list_head to use as a loop cursor.
- * @n: another &struct list_head to use as temporary storage
- * @head: the head for your list.
- *
- * Iterate over an rcu-protected list, safe against removal of list entry.
- *
- * This list-traversal primitive may safely run concurrently with
- * the _rcu list-mutation primitives such as list_add_rcu()
- * as long as the traversal is guarded by rcu_read_lock().
- */
-#define list_for_each_safe_rcu(pos, n, head) \
- for (pos = (head)->next; \
- n = rcu_dereference(pos)->next, pos != (head); \
- pos = n)
+ for (pos = rcu_dereference((head)->next); \
+ pos != (head); \
+ pos = rcu_dereference(pos->next))
/**
* list_for_each_entry_rcu - iterate over rcu list of given type
@@ -668,10 +651,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
* as long as the traversal is guarded by rcu_read_lock().
*/
#define list_for_each_entry_rcu(pos, head, member) \
- for (pos = list_entry((head)->next, typeof(*pos), member); \
- prefetch(rcu_dereference(pos)->member.next), \
- &pos->member != (head); \
- pos = list_entry(pos->member.next, typeof(*pos), member))
+ for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
+ prefetch(pos->member.next), &pos->member != (head); \
+ pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
/**
@@ -686,9 +668,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
* as long as the traversal is guarded by rcu_read_lock().
*/
#define list_for_each_continue_rcu(pos, head) \
- for ((pos) = (pos)->next; \
- prefetch(rcu_dereference((pos))->next), (pos) != (head); \
- (pos) = (pos)->next)
+ for ((pos) = rcu_dereference((pos)->next); \
+ prefetch((pos)->next), (pos) != (head); \
+ (pos) = rcu_dereference((pos)->next))
/*
* Double linked lists with a single pointer list head.
@@ -986,10 +968,10 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
* as long as the traversal is guarded by rcu_read_lock().
*/
#define hlist_for_each_entry_rcu(tpos, pos, head, member) \
- for (pos = (head)->first; \
- rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) && \
+ for (pos = rcu_dereference((head)->first); \
+ pos && ({ prefetch(pos->next); 1;}) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
- pos = pos->next)
+ pos = rcu_dereference(pos->next))
#else
#warning "don't include kernel headers in userspace"