daemon: Integrate checking for an existing pidfile into daemonize_start().

[sliver-openvswitch.git] / lib / daemon.c

diff --git a/lib/daemon.c b/lib/daemon.c
index 9db6c1f..a9cada8 100644 (file)
--- a/lib/daemon.c
+++ b/lib/daemon.c
@@ -107,9 +107,9 @@ is_chdir_enabled(void)
     return chdir_;
 }
 
-/* Normally, die_if_already_running() will terminate the program with a message
- * if a locked pidfile already exists.  If this function is called,
- * die_if_already_running() will merely log a warning. */
+/* Normally, daemonize() or damonize_start() will terminate the program with a
+ * message if a locked pidfile already exists.  If this function is called, an
+ * existing pidfile will be replaced, with a warning. */
 void
 ignore_existing_pidfile(void)
 {
@@ -139,38 +139,20 @@ daemon_set_monitor(void)
     monitor = true;
 }
 
-/* If a pidfile has been configured and that pidfile already exists and is
- * locked by a running process, returns the pid of the running process.
- * Otherwise, returns 0. */
-static pid_t
-already_running(void)
-{
-    pid_t pid = 0;
-    if (pidfile) {
-        int fd = open(pidfile, O_RDWR);
-        if (fd >= 0) {
-            struct flock lck;
-            lck.l_type = F_WRLCK;
-            lck.l_whence = SEEK_SET;
-            lck.l_start = 0;
-            lck.l_len = 0;
-            if (fcntl(fd, F_GETLK, &lck) != -1 && lck.l_type != F_UNLCK) {
-                pid = lck.l_pid;
-            }
-            close(fd);
-        }
-    }
-    return pid;
-}
-
 /* If a locked pidfile exists, issue a warning message and, unless
  * ignore_existing_pidfile() has been called, terminate the program. */
-void
+static void
 die_if_already_running(void)
 {
-    pid_t pid = already_running();
-    if (pid) {
+    pid_t pid;
+    if (!pidfile) {
+        return;
+    }
+    pid = read_pidfile_if_exists(pidfile);
+    if (pid > 0) {
         if (!overwrite_pidfile) {
+            VLOG_ERR("%s: %s already running as pid %ld, aborting",
+                      get_pidfile(), program_name, (long int) pid);
             ovs_fatal(0, "%s: already running as pid %ld",
                       get_pidfile(), (long int) pid);
         } else {
@@ -223,11 +205,11 @@ make_pidfile(void)
                                      pidfile, strerror(errno));
                         }
                     }
-                    free(text);
                 } else {
                     VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
                     close(fd);
                 }
+                free(text);
             } else {
                 VLOG_ERR("%s: fcntl failed: %s", tmpfile, strerror(errno));
                 close(fd);
@@ -257,18 +239,17 @@ fork_and_wait_for_startup(int *fdp)
     int fds[2];
     pid_t pid;
 
-    if (pipe(fds) < 0) {
-        ovs_fatal(errno, "pipe failed");
-    }
+    xpipe(fds);
 
     pid = fork();
     if (pid > 0) {
         /* Running in parent process. */
+        size_t bytes_read;
         char c;
 
         close(fds[1]);
         fatal_signal_fork();
-        if (read(fds[0], &c, 1) != 1) {
+        if (read_fully(fds[0], &c, 1, &bytes_read) != 0) {
             int retval;
             int status;
 
@@ -284,7 +265,8 @@ fork_and_wait_for_startup(int *fdp)
                 exit(WEXITSTATUS(status));
             }
 
-            ovs_fatal(errno, "fork child failed to signal startup");
+            VLOG_FATAL("fork child failed to signal startup (%s)",
+                       strerror(errno));
         }
         close(fds[0]);
         *fdp = -1;
@@ -295,7 +277,7 @@ fork_and_wait_for_startup(int *fdp)
         lockfile_postfork();
         *fdp = fds[1];
     } else {
-        ovs_fatal(errno, "could not fork");
+        VLOG_FATAL("fork failed (%s)", strerror(errno));
     }
 
     return pid;
@@ -310,7 +292,7 @@ fork_notify_startup(int fd)
 
         error = write_fully(fd, "", 1, &bytes_written);
         if (error) {
-            ovs_fatal(error, "could not write to pipe");
+            VLOG_FATAL("pipe write failed (%s)", strerror(error));
         }
 
         close(fd);
@@ -364,7 +346,7 @@ monitor_daemon(pid_t daemon_pid)
         } while (retval == -1 && errno == EINTR);
 
         if (retval == -1) {
-            ovs_fatal(errno, "waitpid failed");
+            VLOG_FATAL("waitpid failed (%s)", strerror(errno));
         } else if (retval == daemon_pid) {
             char *s = process_status_msg(status);
             if (should_restart(status)) {
@@ -467,6 +449,7 @@ daemonize_start(void)
         /* Running in daemon process. */
     }
 
+    die_if_already_running();
     make_pidfile();
 
     /* Make sure that the unixctl commands for vlog get registered in a
@@ -475,11 +458,14 @@ daemonize_start(void)
 }
 
 /* If daemonization is configured, then this function notifies the parent
- * process that the child process has completed startup successfully. */
+ * process that the child process has completed startup successfully.
+ *
+ * Calling this function more than once has no additional effect. */
 void
 daemonize_complete(void)
 {
     fork_notify_startup(daemonize_fd);
+    daemonize_fd = -1;
 
     if (detach) {
         setsid();
@@ -487,6 +473,7 @@ daemonize_complete(void)
             ignore(chdir("/"));
         }
         close_standard_fds();
+        detach = false;
     }
 }
 
@@ -503,10 +490,8 @@ daemon_usage(void)
         ovs_rundir(), program_name);
 }
 
-/* Opens and reads a PID from 'pidfile'.  Returns the nonnegative PID if
- * successful, otherwise a negative errno value. */
-pid_t
-read_pidfile(const char *pidfile)
+static pid_t
+read_pidfile__(const char *pidfile, bool must_exist)
 {
     char line[128];
     struct flock lck;
@@ -527,6 +512,9 @@ read_pidfile(const char *pidfile)
 
     file = fopen(pidfile, "r");
     if (!file) {
+        if (errno == ENOENT && !must_exist) {
+            return 0;
+        }
         error = errno;
         VLOG_WARN("%s: open: %s", pidfile, strerror(error));
         goto error;
@@ -575,3 +563,21 @@ error:
     }
     return -error;
 }
+
+/* Opens and reads a PID from 'pidfile'.  Returns the positive PID if
+ * successful, otherwise a negative errno value. */
+pid_t
+read_pidfile(const char *pidfile)
+{
+    return read_pidfile__(pidfile, true);
+}
+
+
+/* Opens and reads a PID from 'pidfile', if it exists.  Returns 0 if 'pidfile'
+ * doesn't exist, the positive PID if successful, otherwise a negative errno
+ * value. */
+pid_t
+read_pidfile_if_exists(const char *pidfile)
+{
+    return read_pidfile__(pidfile, false);
+}