From: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx> Subject: epoll: simplify signal handling Check signals before locking ep->lock, and immediately return -EINTR if there is any signal pending. This saves a few loads, stores, and branches from the hot path and simplifies the loop structure for follow up patches. Link: https://lkml.kernel.org/r/20201106231635.3528496-3-soheil.kdev@xxxxxxxxx Signed-off-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx> Reviewed-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx> Cc: Guantao Liu <guantaol@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/eventpoll.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/fs/eventpoll.c~epoll-simplify-signal-handling +++ a/fs/eventpoll.c @@ -1733,7 +1733,7 @@ static inline struct timespec64 ep_set_m static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, int maxevents, long timeout) { - int res = 0, eavail, timed_out = 0; + int res, eavail, timed_out = 0; u64 slack = 0; wait_queue_entry_t wait; ktime_t expires, *to = NULL; @@ -1780,6 +1780,9 @@ fetch_events: ep_reset_busy_poll_napi_id(ep); do { + if (signal_pending(current)) + return -EINTR; + /* * Internally init_wait() uses autoremove_wake_function(), * thus wait entry is removed from the wait queue on each @@ -1809,15 +1812,12 @@ fetch_events: * important. */ eavail = ep_events_available(ep); - if (!eavail) { - if (signal_pending(current)) - res = -EINTR; - else - __add_wait_queue_exclusive(&ep->wq, &wait); - } + if (!eavail) + __add_wait_queue_exclusive(&ep->wq, &wait); + write_unlock_irq(&ep->lock); - if (!eavail && !res) + if (!eavail) timed_out = !schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS); @@ -1853,14 +1853,14 @@ send_events: * finding more events available and fetching * repeatedly. */ - res = -EINTR; + return -EINTR; } /* * Try to transfer events to user space. In case we get 0 events and * there's still timeout left over, we go trying again in search of * more luck. */ - if (!res && eavail && + if (eavail && !(res = ep_send_events(ep, events, maxevents)) && !timed_out) goto fetch_events; _
