daemon: write pidfile twice, to be able to show errors to user

diff --git a/usual/daemon.c b/usual/daemon.c
index 768a494cb2c285b04e72df121c83a24840f38fdf..7275b2552138719592fb4146155cfa5e5b779c64 100644 (file)
--- a/usual/daemon.c
+++ b/usual/daemon.c
@@ -108,11 +108,13 @@ static void check_pidfile(const char *pidfile)
        }
 }
 
-static void write_pidfile(const char *pidfile)
+static void write_pidfile(const char *pidfile, bool first_write)
 {
        char buf[64];
        pid_t pid;
        int res, fd, len;
+       static int atexit_hook = 0;
+       int flags = O_WRONLY | O_CREAT;
 
        if (!pidfile || !pidfile[0])
                return;
@@ -126,24 +128,31 @@ static void write_pidfile(const char *pidfile)
        pid = getpid();
        snprintf(buf, sizeof(buf), "%u\n", (unsigned)pid);
 
-       fd = open(pidfile, O_WRONLY | O_CREAT | O_EXCL, 0644);
+       /* don't allow overwrite on first write */
+       if (first_write)
+               flags |= O_EXCL;
+
+       fd = open(pidfile, flags, 0644);
        if (fd < 0)
-               fatal_perror("%s", pidfile);
+               fatal_perror("Cannot write pidfile: '%s'", pidfile);
        len = strlen(buf);
 loop:
        res = write(fd, buf, len);
        if (res < 0) {
                if (errno == EINTR)
                        goto loop;
-               fatal_perror("%s", pidfile);
+               fatal_perror("Write to pidfile failed: '%s'", pidfile);
        } else if (res < len) {
                len -= res;
                goto loop;
        }
        close(fd);
 
-       /* only remove when we have it actually written */
-       atexit(remove_pidfile);
+       if (!atexit_hook) {
+               /* only remove when we have it actually written */
+               atexit(remove_pidfile);
+               atexit_hook = 1;
+       }
 }
 
 /*
@@ -162,8 +171,8 @@ void daemonize(const char *pidfile, bool go_background)
 
        if (pidfile && pidfile[0]) {
                check_pidfile(pidfile);
-               if (!go_background)
-                       write_pidfile(pidfile);
+               /* write pidfile twice, to be able to show problems to user */
+               write_pidfile(pidfile, true);
        } else if (go_background)
                fatal("daemon needs pidfile configured");
 
@@ -202,6 +211,6 @@ void daemonize(const char *pidfile, bool go_background)
        if (pid > 0)
                _exit(0);
 
-       write_pidfile(pidfile);
+       write_pidfile(pidfile, false);
 }