diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 34 |
1 files changed, 32 insertions, 2 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 06f4c5ae1451..52954d4637b5 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -307,7 +307,7 @@ static void unlist_file(struct epitems_head *head) static long long_zero; static long long_max = LONG_MAX; -struct ctl_table epoll_table[] = { +static struct ctl_table epoll_table[] = { { .procname = "max_user_watches", .data = &max_user_watches, @@ -319,6 +319,13 @@ struct ctl_table epoll_table[] = { }, { } }; + +static void __init epoll_sysctls_init(void) +{ + register_sysctl("fs/epoll", epoll_table); +} +#else +#define epoll_sysctls_init() do { } while (0) #endif /* CONFIG_SYSCTL */ static const struct file_operations eventpoll_fops; @@ -1058,7 +1065,7 @@ static inline bool list_add_tail_lockless(struct list_head *new, * added to the list from another CPU: the winner observes * new->next == new. */ - if (cmpxchg(&new->next, new, head) != new) + if (!try_cmpxchg(&new->next, &new, head)) return false; /* @@ -1740,6 +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. @@ -1821,8 +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); /* @@ -2378,6 +2407,7 @@ static int __init eventpoll_init(void) /* Allocates slab cache used to allocate "struct eppoll_entry" */ pwq_cache = kmem_cache_create("eventpoll_pwq", sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); + epoll_sysctls_init(); ephead_cache = kmem_cache_create("ep_head", sizeof(struct epitems_head), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); |