X-Git-Url: http://git.tuebingen.mpg.de/?p=dss.git;a=blobdiff_plain;f=daemon.c;h=709785b437041654e3cacd2fd4f252aea8fa4173;hp=b63e5ff57b408a79e62d44349cb9fd9d342b956e;hb=HEAD;hpb=8daf8f3836e745ba07f1aa01252279588574c95a

diff --git a/daemon.c b/daemon.c
index b63e5ff..ad73061 100644
--- a/daemon.c
+++ b/daemon.c
@@ -1,8 +1,4 @@
-/*
- * Copyright (C) 1997-2010 Andre Noll <maan@tuebingen.mpg.de>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* SPDX-License-Identifier: GPL-2.0 */
 
 /** \file daemon.c Some helpers for programs that detach from the console. */
 
@@ -31,24 +27,40 @@
  *
  * \sa fork(2), setsid(2), dup(2).
  */
-void daemon_init(void)
+int daemon_init(void)
 {
 	pid_t pid;
-	int null;
+	int null, fd[2];
 
 	DSS_INFO_LOG(("daemonizing\n"));
+	if (pipe(fd) < 0)
+		goto err;
 	pid = fork();
 	if (pid < 0)
 		goto err;
-	if (pid)
-		exit(EXIT_SUCCESS); /* parent exits */
+	if (pid) {
+		/*
+		 * The parent process exits once it has received one byte from
+		 * the reading end of the pipe. If the child exits before it
+		 * was able to complete its setup (acquire the lock on the
+		 * semaphore), the read() below will return zero. In this case
+		 * we let the parent die unsuccessfully.
+		 */
+		char c;
+		int ret;
+		close(fd[1]);
+		ret = read(fd[0], &c, 1);
+		if (ret <= 0) {
+			DSS_EMERG_LOG(("child terminated unexpectedly\n"));
+			exit(EXIT_FAILURE);
+		}
+		exit(EXIT_SUCCESS);
+	}
+	close(fd[0]);
 	/* become session leader */
 	if (setsid() < 0)
 		goto err;
-	if (chdir("/") < 0)
-		goto err;
-	umask(0);
-	null = open("/dev/null", O_RDONLY);
+	null = open("/dev/null", O_RDWR);
 	if (null < 0)
 		goto err;
 	if (dup2(null, STDIN_FILENO) < 0)
@@ -58,7 +70,7 @@ void daemon_init(void)
 	if (dup2(null, STDERR_FILENO) < 0)
 		goto err;
 	close(null);
-	return;
+	return fd[1];
 err:
 	DSS_EMERG_LOG(("fatal: %s\n", strerror(errno)));
 	exit(EXIT_FAILURE);