VLOG_DEFINE_THIS_MODULE(daemon);
/* --detach: Should we run in the background? */
-static bool detach;
+static bool detach; /* Was --detach specified? */
+static bool detached; /* Have we already detached? */
/* --pidfile: Name of pidfile (null if none). */
static char *pidfile;
int error;
/* Create a temporary pidfile. */
- tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
- fatal_signal_add_file_to_unlink(tmpfile);
- file = fopen(tmpfile, "w+");
+ if (overwrite_pidfile) {
+ tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
+ fatal_signal_add_file_to_unlink(tmpfile);
+ } else {
+ /* Everyone shares the same file which will be treated as a lock. To
+ * avoid some uncomfortable race conditions, we can't set up the fatal
+ * signal unlink until we've acquired it. */
+ tmpfile = xasprintf("%s.tmp", pidfile);
+ }
+
+ file = fopen(tmpfile, "a+");
if (!file) {
VLOG_FATAL("%s: create failed (%s)", tmpfile, strerror(errno));
}
+ error = lock_pidfile(file, F_SETLK);
+ if (error) {
+ /* Looks like we failed to acquire the lock. Note that, if we failed
+ * for some other reason (and '!overwrite_pidfile'), we will have
+ * left 'tmpfile' as garbage in the file system. */
+ VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", tmpfile, strerror(error));
+ }
+
+ if (!overwrite_pidfile) {
+ /* We acquired the lock. Make sure to clean up on exit, and verify
+ * that we're allowed to create the actual pidfile. */
+ fatal_signal_add_file_to_unlink(tmpfile);
+ check_already_running();
+ }
+
if (fstat(fileno(file), &s) == -1) {
VLOG_FATAL("%s: fstat failed (%s)", tmpfile, strerror(errno));
}
+ if (ftruncate(fileno(file), 0) == -1) {
+ VLOG_FATAL("%s: truncate failed (%s)", tmpfile, strerror(errno));
+ }
+
fprintf(file, "%ld\n", pid);
if (fflush(file) == EOF) {
VLOG_FATAL("%s: write failed (%s)", tmpfile, strerror(errno));
}
- error = lock_pidfile(file, F_SETLK);
- if (error) {
- VLOG_FATAL("%s: fcntl(F_SETLK) failed (%s)", tmpfile, strerror(error));
- }
+ error = rename(tmpfile, pidfile);
- /* Rename or link it to the correct name. */
- if (overwrite_pidfile) {
- if (rename(tmpfile, pidfile) < 0) {
- VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
- tmpfile, pidfile, strerror(errno));
- }
- } else {
- do {
- error = link(tmpfile, pidfile) == -1 ? errno : 0;
- if (error == EEXIST) {
- check_already_running();
- }
- } while (error == EINTR || error == EEXIST);
- if (error) {
- VLOG_FATAL("failed to link \"%s\" as \"%s\" (%s)",
- tmpfile, pidfile, strerror(error));
- }
+ /* Due to a race, 'tmpfile' may be owned by a different process, so we
+ * shouldn't delete it on exit. */
+ fatal_signal_remove_file_to_unlink(tmpfile);
+
+ if (error < 0) {
+ VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
+ tmpfile, pidfile, strerror(errno));
}
/* Ensure that the pidfile will get deleted on exit. */
fatal_signal_add_file_to_unlink(pidfile);
- /* Delete the temporary pidfile if it still exists. */
- if (!overwrite_pidfile) {
- error = fatal_signal_unlink_file_now(tmpfile);
- if (error) {
- VLOG_FATAL("%s: unlink failed (%s)", tmpfile, strerror(error));
- }
- }
-
/* Clean up.
*
* We don't close 'file' because its file descriptor must remain open to
daemonize_complete();
}
+/* Calls fork() and on success returns its return value. On failure, logs an
+ * error and exits unsuccessfully.
+ *
+ * Post-fork, but before returning, this function calls a few other functions
+ * that are generally useful if the child isn't planning to exec a new
+ * process. */
+pid_t
+fork_and_clean_up(void)
+{
+ pid_t pid;
+
+ pid = fork();
+ if (pid > 0) {
+ /* Running in parent process. */
+ fatal_signal_fork();
+ } else if (!pid) {
+ /* Running in child process. */
+ time_postfork();
+ lockfile_postfork();
+ } else {
+ VLOG_FATAL("fork failed (%s)", strerror(errno));
+ }
+
+ return pid;
+}
+
+/* Forks, then:
+ *
+ * - In the parent, waits for the child to signal that it has completed its
+ * startup sequence. Then stores -1 in '*fdp' and returns the child's pid.
+ *
+ * - In the child, stores a fd in '*fdp' and returns 0. The caller should
+ * pass the fd to fork_notify_startup() after it finishes its startup
+ * sequence.
+ *
+ * If something goes wrong with the fork, logs a critical error and aborts the
+ * process. */
static pid_t
fork_and_wait_for_startup(int *fdp)
{
xpipe(fds);
- pid = fork();
+ pid = fork_and_clean_up();
if (pid > 0) {
/* Running in parent process. */
size_t bytes_read;
char c;
close(fds[1]);
- fatal_signal_fork();
if (read_fully(fds[0], &c, 1, &bytes_read) != 0) {
int retval;
int status;
} else if (!pid) {
/* Running in child process. */
close(fds[0]);
- time_postfork();
- lockfile_postfork();
*fdp = fds[1];
- } else {
- VLOG_FATAL("fork failed (%s)", strerror(errno));
}
return pid;
monitor_daemon(pid_t daemon_pid)
{
/* XXX Should log daemon's stderr output at startup time. */
- const char *saved_program_name;
time_t last_restart;
char *status_msg;
int crashes;
- saved_program_name = program_name;
- program_name = xasprintf("monitor(%s)", program_name);
+ subprogram_name = "monitor";
status_msg = xstrdup("healthy");
last_restart = TIME_MIN;
crashes = 0;
int retval;
int status;
- proctitle_set("%s: monitoring pid %lu (%s)",
- saved_program_name, (unsigned long int) daemon_pid,
- status_msg);
+ proctitle_set("monitoring pid %lu (%s)",
+ (unsigned long int) daemon_pid, status_msg);
do {
retval = waitpid(daemon_pid, &status, 0);
/* Running in new daemon process. */
proctitle_restore();
- free((char *) program_name);
- program_name = saved_program_name;
+ subprogram_name = "";
}
/* Close standard file descriptors (except any that the client has requested we
}
/* 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. It also
+ * call daemonize_post_detach().
*
* Calling this function more than once has no additional effect. */
void
daemonize_complete(void)
{
- fork_notify_startup(daemonize_fd);
- daemonize_fd = -1;
+ if (!detached) {
+ detached = true;
+
+ fork_notify_startup(daemonize_fd);
+ daemonize_fd = -1;
+ daemonize_post_detach();
+ }
+}
+/* If daemonization is configured, then this function does traditional Unix
+ * daemonization behavior: join a new session, chdir to the root (if not
+ * disabled), and close the standard file descriptors.
+ *
+ * It only makes sense to call this function as part of an implementation of a
+ * special daemon subprocess. A normal daemon should just call
+ * daemonize_complete(). */
+void
+daemonize_post_detach(void)
+{
if (detach) {
setsid();
if (chdir_) {
ignore(chdir("/"));
}
close_standard_fds();
- detach = false;
}
}
projects / openvswitch / blobdiff