X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng%2Fcommands%2Fcreate.c;h=94c1c61836f5edd61dc5c4b8784d346875d0284b;hp=ba62940c62fbb4dec65057d9942250d6c7d8fa7a;hb=92360082fd291a95695fb612d773ae1bb991c256;hpb=c1de15c4908d6bf5d2ca34b2542b18ef9b0bfb87

diff --git a/src/bin/lttng/commands/create.c b/src/bin/lttng/commands/create.c
index ba62940c6..94c1c6183 100644
--- a/src/bin/lttng/commands/create.c
+++ b/src/bin/lttng/commands/create.c
@@ -27,6 +27,7 @@
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
+#include <signal.h>
 
 #include <common/mi-lttng.h>
 
@@ -550,6 +551,120 @@ error:
 	return ret;
 }
 
+/*
+ *  spawn_sessiond
+ *
+ *  Spawn a session daemon by forking and execv.
+ */
+static int spawn_sessiond(char *pathname)
+{
+	int ret = 0;
+	pid_t pid;
+
+	MSG("Spawning a session daemon");
+	recv_child_signal = 0;
+	pid = fork();
+	if (pid == 0) {
+		/*
+		 * Spawn session daemon and tell
+		 * it to signal us when ready.
+		 */
+		execlp(pathname, "lttng-sessiond", "--sig-parent", "--quiet", NULL);
+		/* execlp only returns if error happened */
+		if (errno == ENOENT) {
+			ERR("No session daemon found. Use --sessiond-path.");
+		} else {
+			PERROR("execlp");
+		}
+		kill(getppid(), SIGTERM);	/* wake parent */
+		exit(EXIT_FAILURE);
+	} else if (pid > 0) {
+		sessiond_pid = pid;
+		/*
+		 * 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);
+		}
+		/*
+		 * The signal handler will nullify sessiond_pid on SIGCHLD
+		 */
+		if (!sessiond_pid) {
+			exit(EXIT_FAILURE);
+		}
+		goto end;
+	} else {
+		PERROR("fork");
+		ret = -1;
+		goto end;
+	}
+
+end:
+	return ret;
+}
+
+/*
+ *  launch_sessiond
+ *
+ *  Check if the session daemon is available using
+ *  the liblttngctl API for the check. If not, try to
+ *  spawn a daemon.
+ */
+static int launch_sessiond(void)
+{
+	int ret;
+	char *pathname = NULL;
+
+	ret = lttng_session_daemon_alive();
+	if (ret) {
+		/* Sessiond is alive, not an error */
+		ret = 0;
+		goto end;
+	}
+
+	/* Try command line option path */
+	pathname = opt_sessiond_path;
+
+	/* Try LTTNG_SESSIOND_PATH env variable */
+	if (pathname == NULL) {
+		pathname = getenv(DEFAULT_SESSIOND_PATH_ENV);
+	}
+
+	/* Try with configured path */
+	if (pathname == NULL) {
+		if (CONFIG_SESSIOND_BIN[0] != '\0') {
+			pathname = CONFIG_SESSIOND_BIN;
+		}
+	}
+
+	/* Try the default path */
+	if (pathname == NULL) {
+		pathname = INSTALL_BIN_PATH "/lttng-sessiond";
+	}
+
+	DBG("Session daemon binary path: %s", pathname);
+
+	/* Check existence and permissions */
+	ret = access(pathname, F_OK | X_OK);
+	if (ret < 0) {
+		ERR("No such file or access denied: %s", pathname);
+		goto end;
+	}
+
+	ret = spawn_sessiond(pathname);
+	if (ret < 0) {
+		ERR("Problem occurred when starting %s", pathname);
+	}
+end:
+	return ret;
+}
+
 /*
  *  The 'create <options>' first level command
  *
@@ -619,6 +734,15 @@ int cmd_create(int argc, const char **argv)
 		goto end;
 	}
 
+	/* Spawn a session daemon if needed */
+	if (!opt_no_sessiond) {
+		ret = launch_sessiond();
+		if (ret) {
+			ret = CMD_ERROR;
+			goto end;
+		}
+	}
+
 	/* MI initialization */
 	if (lttng_opt_mi) {
 		writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);