diff options
| -rw-r--r-- | include/linux/list.h | 20 | ||||
| -rw-r--r-- | kernel/sched/wait.c | 2 | ||||
| -rw-r--r-- | mm/filemap.c | 7 |
3 files changed, 21 insertions, 8 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index aff44d34f4e4..0d0d17a10d25 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -283,6 +283,24 @@ static inline int list_empty(const struct list_head *head) } /** + * list_del_init_careful - deletes entry from list and reinitialize it. + * @entry: the element to delete from the list. + * + * This is the same as list_del_init(), except designed to be used + * together with list_empty_careful() in a way to guarantee ordering + * of other memory operations. + * + * Any memory operations done before a list_del_init_careful() are + * guaranteed to be visible after a list_empty_careful() test. + */ +static inline void list_del_init_careful(struct list_head *entry) +{ + __list_del_entry(entry); + entry->prev = entry; + smp_store_release(&entry->next, entry); +} + +/** * list_empty_careful - tests whether a list is empty and not being modified * @head: the list to test * @@ -297,7 +315,7 @@ static inline int list_empty(const struct list_head *head) */ static inline int list_empty_careful(const struct list_head *head) { - struct list_head *next = head->next; + struct list_head *next = smp_load_acquire(&head->next); return (next == head) && (next == head->prev); } diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index ba059fbfc53a..01f5d3020589 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -389,7 +389,7 @@ int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, i int ret = default_wake_function(wq_entry, mode, sync, key); if (ret) - list_del_init(&wq_entry->entry); + list_del_init_careful(&wq_entry->entry); return ret; } diff --git a/mm/filemap.c b/mm/filemap.c index 8c3d3e233d37..991503bbf922 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1041,13 +1041,8 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, * since after list_del_init(&wait->entry) the wait entry * might be de-allocated and the process might even have * exited. - * - * We _really_ should have a "list_del_init_careful()" to - * properly pair with the unlocked "list_empty_careful()" - * in finish_wait(). */ - smp_mb(); - list_del_init(&wait->entry); + list_del_init_careful(&wait->entry); return ret; } |