A smp_read_barrier_depends() appears to be missing in llist_del_first(). It should only matter for Alpha in practice. Adding it after the check of entry against NULL allows skipping the barrier in a common case.
Signed-off-by: Mathieu Desnoyers <[email protected]> CC: Huang Ying <[email protected]> CC: Paul McKenney <[email protected]> CC: David Howells <[email protected]> --- lib/llist.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/lib/llist.c b/lib/llist.c index f76196d..72861f3 100644 --- a/lib/llist.c +++ b/lib/llist.c @@ -26,6 +26,7 @@ #include <linux/export.h> #include <linux/interrupt.h> #include <linux/llist.h> +#include <asm/barrier.h> /** @@ -72,6 +73,12 @@ struct llist_node *llist_del_first(struct llist_head *head) if (entry == NULL) return NULL; old_entry = entry; + /* + * Load entry before entry->next. Matches the implicit + * memory barrier before the cmpxchg in llist_add_batch(), + * which ensures entry->next is stored before entry. + */ + smp_read_barrier_depends(); next = entry->next; entry = cmpxchg(&head->first, old_entry, next); if (entry == old_entry) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
