From: Olivier Houchard <ohouchard@haproxy.com>
Date: Tue, 25 Feb 2025 11:01:40 +0000 (+0100)
Subject: MEDIUM: epoll: Make sure we can add a new event
X-Git-Tag: v3.2-dev7~62
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=752c5cba5dc068a472bce344586e1b8c54021367;p=thirdparty%2Fhaproxy.git

MEDIUM: epoll: Make sure we can add a new event

Check that the call to epoll_ctl() succeeds, and if it does not, if
we're adding a new event and it fails with EEXIST, then delete and
re-add the event. There are a few cases where we may already have events
for a fd. If epoll_ctl() fails for any reason, use BUG_ON to make sure
we immediately crash, as this should not happen.
---

diff --git a/src/ev_epoll.c b/src/ev_epoll.c
index 21770aa35..e0dd52158 100644
--- a/src/ev_epoll.c
+++ b/src/ev_epoll.c
@@ -154,7 +154,14 @@ static void _update_fd(int fd)
  done:
 	ev.events &= ~epoll_mask;
 	ev.data.u64 = ((u64)fdtab[fd].generation << 32) + fd;
-	epoll_ctl(epoll_fd[tid], opcode, fd, &ev);
+	if (epoll_ctl(epoll_fd[tid], opcode, fd, &ev) != 0) {
+		if (opcode == EPOLL_CTL_ADD && errno == EEXIST) {
+			BUG_ON(epoll_ctl(epoll_fd[tid], EPOLL_CTL_DEL, fd, &ev) != 0);
+			BUG_ON(epoll_ctl(epoll_fd[tid], EPOLL_CTL_ADD, fd, &ev) != 0);
+		} else {
+			BUG_ON(1, "epoll_ctl() failed when it should not");
+		}
+	}
 }
 
 /*