From ea96ef48cbf4980b7dd3dd61f944091ead821f20 Mon Sep 17 00:00:00 2001
From: "C. McEnroe" <june@causal.agency>
Date: Mon, 17 Aug 2020 16:06:40 -0400
Subject: Use a non-blocking lock on the PID file

---
 daemon.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/daemon.c b/daemon.c
index 1643200..a1be594 100644
--- a/daemon.c
+++ b/daemon.c
@@ -247,11 +247,13 @@ int main(int argc, char *argv[]) {
 
 	int pidFile = -1;
 	if (pidPath) {
-		pidFile = open(
-			pidPath, O_WRONLY | O_CREAT | O_EXLOCK | O_CLOEXEC, 0600
-		);
+		pidFile = open(pidPath, O_WRONLY | O_CREAT | O_CLOEXEC, 0600);
 		if (pidFile < 0) err(EX_CANTCREAT, "%s", pidPath);
 
+		error = flock(pidFile, LOCK_EX | LOCK_NB);
+		if (error && errno != EWOULDBLOCK) err(EX_IOERR, "%s", pidPath);
+		if (error) errx(EX_CANTCREAT, "%s: file is locked", pidPath);
+
 		error = ftruncate(pidFile, 0);
 		if (error) err(EX_IOERR, "%s", pidPath);
 	}
-- 
cgit 1.4.1