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author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-20 21:59:13 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-04-21 08:23:35 -0700 |
commit | cc216c5d429892872f70f76975e243aef7ad9db1 (patch) | |
tree | 6455048df83fb61c870367f7a88e701e44ebdd24 /include/linux/list.h | |
parent | 3925e6fc1f774048404fdd910b0345b06c699eb4 (diff) | |
download | kernel_samsung_espresso10-cc216c5d429892872f70f76975e243aef7ad9db1.zip kernel_samsung_espresso10-cc216c5d429892872f70f76975e243aef7ad9db1.tar.gz kernel_samsung_espresso10-cc216c5d429892872f70f76975e243aef7ad9db1.tar.bz2 |
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>
Diffstat (limited to 'include/linux/list.h')
-rw-r--r-- | include/linux/list.h | 48 |
1 files changed, 15 insertions, 33 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index 75ce2cb..dac16f9 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" |