From d90513ea85693da0ca5955173609f4e81e38ae16 Mon Sep 17 00:00:00 2001
From: Christian Ullrich <chris@chrullrich.net>
Date: Sun, 3 May 2026 17:35:10 +0200
Subject: [PATCH] lockf: Avoid spinning when operating on an fd

When operating on a file descriptor, acquire_lock() would ignore the
flags argument and always operate in non-blocking mode, resulting in
unnecessary busy-looping.

PR:		294832
MFC after:	1 week
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D56722
---
 usr.bin/lockf/lockf.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/usr.bin/lockf/lockf.c b/usr.bin/lockf/lockf.c
index 16bae36a21e..076d28b7ddd 100644
--- a/usr.bin/lockf/lockf.c
+++ b/usr.bin/lockf/lockf.c
@@ -320,10 +320,14 @@ acquire_lock(union lock_subject *subj, int flags, int silent)
 	int fd;
 
 	if (fdlock) {
+		int lflags = LOCK_EX;
+
 		assert(subj->subj_fd >= 0 && subj->subj_fd <= INT_MAX);
 		fd = (int)subj->subj_fd;
 
-		if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
+		if ((flags & O_NONBLOCK) == O_NONBLOCK)
+			lflags |= LOCK_NB;
+		if (flock(fd, lflags) == -1) {
 			if (errno == EAGAIN || errno == EINTR)
 				return (-1);
 			err(EX_CANTCREAT, "cannot lock fd %d", fd);