From ef6f20ce47613db7cc615b45f4b6fa1eb99ae0ba Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Sat, 18 Feb 2023 20:04:29 -0700
Subject: [PATCH] tail: Retry kevent if the system call was interrupted

kevent returns EINTR when I suspend / resume. This causes tail -f
and tail -F to exit with interrupt system call. Ignore this error
and try kevent again.

Sponsored by:		Netflix
---
 usr.bin/tail/forward.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
index 3897d115effd..6dbeb9cdd047 100644
--- a/usr.bin/tail/forward.c
+++ b/usr.bin/tail/forward.c
@@ -411,10 +411,16 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 			/*
 			 * In the -F case we set a timeout to ensure that
 			 * we re-stat the file at least once every second.
+			 * If we've recieved EINTR, ignore it. Both reasons
+			 * for its generation are transient.
 			 */
-			n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
-			if (n < 0)
-				err(1, "kevent");
+			do {
+				n = kevent(kq, NULL, 0, ev, 1, Fflag ? &ts : NULL);
+				if (n < 0 && errno == EINTR)
+					continue;
+				if (n < 0)
+					err(1, "kevent");
+			} while (n < 0);
 			if (n == 0) {
 				/* timeout */
 				break;