diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/eventpoll.h | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h index ea9ca0e4172a..728fb5dee5ed 100644 --- a/include/linux/eventpoll.h +++ b/include/linux/eventpoll.h @@ -39,12 +39,16 @@ static inline void eventpoll_release(struct file *file) { /* - * Fast check to avoid the get/release of the semaphore. Since - * we're doing this outside the semaphore lock, it might return - * false negatives, but we don't care. It'll help in 99.99% of cases - * to avoid the semaphore lock. False positives simply cannot happen - * because the file in on the way to be removed and nobody ( but - * eventpoll ) has still a reference to this file. + * Fast check to skip the slow path in the common case where the + * file was never attached to an epoll. Safe without file->f_lock + * because every f_ep writer excludes a concurrent __fput() on + * @file: + * - ep_insert() requires the file alive (refcount > 0); + * - ep_remove() holds @file pinned via epi_fget() across the + * write; + * - eventpoll_release_file() runs from __fput() itself. + * We are in __fput() here, so none of those can race us: a NULL + * observation truly means no epoll path has work left on @file. */ if (likely(!READ_ONCE(file->f_ep))) return; |