static int opt_no_sessiond;
static char *opt_sessiond_path;
static pid_t sessiond_pid;
+static volatile int recv_child_signal;
enum {
OPT_SESSION_PATH,
static void usage(FILE *ofp)
{
fprintf(ofp, "LTTng Trace Control " VERSION"\n\n");
- fprintf(ofp, "usage: lttng [options] <command>\n");
+ fprintf(ofp, "usage: lttng [OPTIONS] <COMMAND>\n");
fprintf(ofp, "\n");
fprintf(ofp, "Options:\n");
fprintf(ofp, " -h, --help Show this help\n");
- fprintf(ofp, " -g, --group NAME Unix tracing group name. (default: tracing)\n");
- fprintf(ofp, " -v, --verbose Verbose mode\n");
+ fprintf(ofp, " --list-options Simple listing of lttng options\n");
+ fprintf(ofp, " --list-commands Simple listing of lttng commands\n");
+ fprintf(ofp, " -v, --verbose Increase verbosity\n");
fprintf(ofp, " -q, --quiet Quiet mode\n");
+ fprintf(ofp, " -g, --group NAME Unix tracing group name. (default: tracing)\n");
fprintf(ofp, " -n, --no-sessiond Don't spawn a session daemon\n");
fprintf(ofp, " --sessiond-path Session daemon full path\n");
- fprintf(ofp, " --list-options Simple listing of lttng options\n");
- fprintf(ofp, " --list-commands Simple listing of lttng commands\n");
fprintf(ofp, "\n");
fprintf(ofp, "Commands:\n");
- fprintf(ofp, " add-context Add context to event or/and channel\n");
+ fprintf(ofp, " add-context Add context to event and/or channel\n");
fprintf(ofp, " calibrate Quantify LTTng overhead\n");
fprintf(ofp, " create Create tracing session\n");
- fprintf(ofp, " destroy Teardown tracing session\n");
+ fprintf(ofp, " destroy Tear down tracing session\n");
fprintf(ofp, " enable-channel Enable tracing channel\n");
fprintf(ofp, " enable-event Enable tracing event\n");
fprintf(ofp, " disable-channel Disable tracing channel\n");
case SIGCHLD:
DBG("SIGCHLD caugth");
waitpid(sessiond_pid, &status, 0);
+ recv_child_signal = 1;
/* Indicate that the session daemon died */
sessiond_pid = 0;
ERR("Session daemon died (exit status %d)", WEXITSTATUS(status));
break;
case SIGUSR1:
/* Notify is done */
+ recv_child_signal = 1;
DBG("SIGUSR1 caugth");
break;
default:
pid_t pid;
MSG("Spawning a session daemon");
+ recv_child_signal = 0;
pid = fork();
if (pid == 0) {
/*
} else {
perror("execlp");
}
- kill(getppid(), SIGTERM); /* unpause parent */
+ kill(getppid(), SIGTERM); /* wake parent */
exit(EXIT_FAILURE);
} else if (pid > 0) {
sessiond_pid = pid;
- /* Wait for lttng-sessiond to start */
- pause();
+ /*
+ * Wait for lttng-sessiond to start. We need to use a
+ * flag to check if the signal has been sent to us,
+ * because the child can be scheduled before the parent,
+ * and thus send the signal before this check. In the
+ * signal handler, we set the recv_child_signal flag, so
+ * anytime we check it after the fork is fine. Note that
+ * sleep() is interrupted before the 1 second delay as
+ * soon as the signal is received, so it will not cause
+ * visible delay for the user.
+ */
+ while (!recv_child_signal) {
+ sleep(1);
+ }
if (!sessiond_pid) {
exit(EXIT_FAILURE);
}