Improve comment of snapshot_currently_being_removed.

[dss.git] / daemon.c

diff --git a/daemon.c b/daemon.c
index e9cf7b056d674a00e10a7b4efef0eef64331361f..709785b437041654e3cacd2fd4f252aea8fa4173 100644 (file)
--- a/daemon.c
+++ b/daemon.c
@@ -1,8 +1,4 @@
-/*
- * Copyright (C) 1997-2008 Andre Noll <maan@systemlinux.org>
- *
- * 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. */
 
@@ -19,9 +15,10 @@
 #include <stdio.h>
 
 #include "gcc-compat.h"
-#include "error.h"
+#include "err.h"
 #include "log.h"
-#include "string.h"
+#include "str.h"
+#include "daemon.h"
 
 /**
  * Do the usual stuff to become a daemon.
@@ -30,24 +27,41 @@
  *
  * \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");
+       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)
@@ -57,9 +71,9 @@ 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));
+       DSS_EMERG_LOG(("fatal: %s\n", strerror(errno)));
        exit(EXIT_FAILURE);
 }
 
@@ -77,8 +91,8 @@ FILE *open_log(const char *logfile_name)
        assert(logfile_name);
        logfile = fopen(logfile_name, "a");
        if (!logfile) {
-               DSS_EMERG_LOG("can not open %s: %s\n", logfile_name,
-                       strerror(errno));
+               DSS_EMERG_LOG(("can not open %s: %s\n", logfile_name,
+                       strerror(errno)));
                exit(EXIT_FAILURE);
        }
        setlinebuf(logfile);
@@ -96,7 +110,7 @@ void close_log(FILE* logfile)
 {
        if (!logfile)
                return;
-       DSS_INFO_LOG("closing logfile\n");
+       DSS_INFO_LOG(("closing logfile\n"));
        fclose(logfile);
 }
 
@@ -105,6 +119,6 @@ void close_log(FILE* logfile)
  */
 void log_welcome(int loglevel)
 {
-       DSS_INFO_LOG("***** welcome to dss ******\n");
-       DSS_DEBUG_LOG("using loglevel %d\n", loglevel);
+       DSS_INFO_LOG(("***** welcome to dss ******\n"));
+       DSS_DEBUG_LOG(("using loglevel %d\n", loglevel));
 }