Commit 2efdaf76 authored by Soheil Hassas Yeganeh's avatar Soheil Hassas Yeganeh Committed by Linus Torvalds
Browse files

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@gmail.com


Signed-off-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Reviewed-by: default avatarKhazhismel Kumykov <khazhy@google.com>
Cc: Guantao Liu <guantaol@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 289caf5d

fs/eventpoll.c

+10 −10
Original line number Diff line number Diff line
@@ -1733,7 +1733,7 @@ static inline struct timespec64 ep_set_mstimeout(long ms) 
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

		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;

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