linux-kernel - [PATCH 3/8] epoll: pull fatal signal checks into ep_send

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Date:   Fri,  6 Nov 2020 18:16:30 -0500
From:   Soheil Hassas Yeganeh <soheil.kdev@...il.com>
To:     torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        dave@...olabs.net, edumazet@...gle.com, willemb@...gle.com,
        khazhy@...gle.com, guantaol@...gle.com,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: [PATCH 3/8] epoll: pull fatal signal checks into ep_send_events()

From: Soheil Hassas Yeganeh <soheil@...gle.com>

To simplify the code, pull in checking the fatal signals into
ep_send_events().  ep_send_events() is called only from ep_poll().

Note that, previously, we were always checking fatal events, but
it is checked only if eavail is true.  This should be fine because
the goal of that check is to quickly return from epoll_wait() when
there is a pending fatal signal.

Suggested-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Khazhismel Kumykov <khazhy@...gle.com>
---
 fs/eventpoll.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 80c560dad6a3..ed9deeab2488 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1780,6 +1780,14 @@ static int ep_send_events(struct eventpoll *ep,
 {
 	struct ep_send_events_data esed;
 
+	/*
+	 * Always short-circuit for fatal signals to allow threads to make a
+	 * timely exit without the chance of finding more events available and
+	 * fetching repeatedly.
+	 */
+	if (fatal_signal_pending(current))
+		return -EINTR;
+
 	esed.maxevents = maxevents;
 	esed.events = events;
 
@@ -1931,15 +1939,6 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 	}
 
 send_events:
-	if (fatal_signal_pending(current)) {
-		/*
-		 * Always short-circuit for fatal signals to allow
-		 * threads to make a timely exit without the chance of
-		 * finding more events available and fetching
-		 * repeatedly.
-		 */
-		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
-- 
2.29.1.341.ge80a0c044ae-goog