diff options
Diffstat (limited to 'kernel/futex.c')
-rw-r--r-- | kernel/futex.c | 21 |
1 files changed, 6 insertions, 15 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index aca8d10704f..5e71a6bf6f6 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -201,21 +201,6 @@ static int get_futex_key(unsigned long uaddr, union futex_key *key) * from swap. But that's a lot of code to duplicate here * for a rare case, so we simply fetch the page. */ - - /* - * Do a quick atomic lookup first - this is the fastpath. - */ - page = follow_page(mm, uaddr, FOLL_TOUCH|FOLL_GET); - if (likely(page != NULL)) { - key->shared.pgoff = - page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); - put_page(page); - return 0; - } - - /* - * Do it the general way. - */ err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL); if (err >= 0) { key->shared.pgoff = @@ -285,7 +270,13 @@ static void wake_futex(struct futex_q *q) /* * The waiting task can free the futex_q as soon as this is written, * without taking any locks. This must come last. + * + * A memory barrier is required here to prevent the following store + * to lock_ptr from getting ahead of the wakeup. Clearing the lock + * at the end of wake_up_all() does not prevent this store from + * moving. */ + wmb(); q->lock_ptr = NULL; } |