diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index e2daa940ebce..8b56b94e2f56 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1747,6 +1747,21 @@ static struct timespec64 *ep_timeout_to_timespec(struct timespec64 *to, long ms) return to; } +/* + * autoremove_wake_function, but remove even on failure to wake up, because we + * know that default_wake_function/ttwu will only fail if the thread is already + * woken, and in that case the ep_poll loop will remove the entry anyways, not + * try to reuse it. + */ +static int ep_autoremove_wake_function(struct wait_queue_entry *wq_entry, + unsigned int mode, int sync, void *key) +{ + int ret = default_wake_function(wq_entry, mode, sync, key); + + list_del_init(&wq_entry->entry); + return ret; +} + /** * ep_poll - Retrieves ready events, and delivers them to the caller-supplied * event buffer. @@ -1828,8 +1843,15 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, * normal wakeup path no need to call __remove_wait_queue() * explicitly, thus ep->lock is not taken, which halts the * event delivery. + * + * In fact, we now use an even more aggressive function that + * unconditionally removes, because we don't reuse the wait + * entry between loop iterations. This lets us also avoid the + * performance issue if a process is killed, causing all of its + * threads to wake up without being removed normally. */ init_wait(&wait); + wait.func = ep_autoremove_wake_function; write_lock_irq(&ep->lock); /* |