X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fcmd.c;h=bba77023a6415ff0b52e9f0dcfde6729c5a0856f;hb=a1dcaf0fdbfbaf02ef38886b556c3d37e4458fdc;hp=cbf2bceff27908a164128ce27328459b4e5cfadf;hpb=e43c41c57a0087c782ca0ec29d6613364605d31d;p=lttng-tools.git

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index cbf2bceff..bba77023a 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -856,6 +856,15 @@ int cmd_enable_channel(struct ltt_session *session,
 
 	DBG("Enabling channel %s for session %s", attr->name, session->name);
 
+	/*
+	 * Don't try to enable a channel if the session has been started at
+	 * some point in time before. The tracer does not allow it.
+	 */
+	if (session->started) {
+		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+		goto error;
+	}
+
 	rcu_read_lock();
 
 	switch (domain->type) {
@@ -876,18 +885,6 @@ int cmd_enable_channel(struct ltt_session *session,
 		}
 
 		kernel_wait_quiescent(kernel_tracer_fd);
-
-		/*
-		 * If the session was previously started, start as well this newly
-		 * created kernel session so the events/channels enabled *after* the
-		 * start actually work.
-		 */
-		if (session->started && !session->kernel_session->started) {
-			ret = start_kernel_session(session->kernel_session, wpipe);
-			if (ret != LTTNG_OK) {
-				goto error;
-			}
-		}
 		break;
 	}
 	case LTTNG_DOMAIN_UST:
@@ -902,17 +899,6 @@ int cmd_enable_channel(struct ltt_session *session,
 		} else {
 			ret = channel_ust_enable(usess, uchan);
 		}
-
-		/* Start the UST session if the session was already started. */
-		if (session->started && !usess->start_trace) {
-			ret = ust_app_start_trace_all(usess);
-			if (ret < 0) {
-				ret = LTTNG_ERR_UST_START_FAIL;
-				goto error;
-			}
-			ret = LTTNG_OK;
-			usess->start_trace = 1;
-		}
 		break;
 	}
 	default:
@@ -1076,7 +1062,7 @@ error:
 int cmd_add_context(struct ltt_session *session, int domain,
 		char *channel_name, struct lttng_event_context *ctx, int kwpipe)
 {
-	int ret;
+	int ret, chan_kern_created = 0, chan_ust_created = 0;
 
 	switch (domain) {
 	case LTTNG_DOMAIN_KERNEL:
@@ -1088,6 +1074,7 @@ int cmd_add_context(struct ltt_session *session, int domain,
 			if (ret != LTTNG_OK) {
 				goto error;
 			}
+			chan_kern_created = 1;
 		}
 
 		/* Add kernel context to kernel tracer */
@@ -1118,6 +1105,7 @@ int cmd_add_context(struct ltt_session *session, int domain,
 				goto error;
 			}
 			free(attr);
+			chan_ust_created = 1;
 		}
 
 		ret = context_ust_add(usess, domain, ctx, channel_name);
@@ -1136,9 +1124,30 @@ int cmd_add_context(struct ltt_session *session, int domain,
 		goto error;
 	}
 
-	ret = LTTNG_OK;
+	return LTTNG_OK;
 
 error:
+	if (chan_kern_created) {
+		struct ltt_kernel_channel *kchan =
+			trace_kernel_get_channel_by_name(DEFAULT_CHANNEL_NAME,
+					session->kernel_session);
+		/* Created previously, this should NOT fail. */
+		assert(kchan);
+		kernel_destroy_channel(kchan);
+	}
+
+	if (chan_ust_created) {
+		struct ltt_ust_channel *uchan =
+			trace_ust_find_channel_by_name(
+					session->ust_session->domain_global.channels,
+					DEFAULT_CHANNEL_NAME);
+		/* Created previously, this should NOT fail. */
+		assert(uchan);
+		/* Remove from the channel list of the session. */
+		trace_ust_delete_channel(session->ust_session->domain_global.channels,
+				uchan);
+		trace_ust_destroy_channel(uchan);
+	}
 	return ret;
 }
 
@@ -1553,7 +1562,7 @@ int cmd_stop_trace(struct ltt_session *session)
 	session->enabled = 0;
 
 	/* Kernel tracer */
-	if (ksession) {
+	if (ksession && ksession->started) {
 		DBG("Stop kernel tracing");
 
 		/* Flush metadata if exist */
@@ -1583,7 +1592,7 @@ int cmd_stop_trace(struct ltt_session *session)
 		ksession->started = 0;
 	}
 
-	if (usess) {
+	if (usess && usess->start_trace) {
 		usess->start_trace = 0;
 
 		ret = ust_app_stop_trace_all(usess);
@@ -1593,8 +1602,6 @@ int cmd_stop_trace(struct ltt_session *session)
 		}
 	}
 
-	session->started = 0;
-
 	ret = LTTNG_OK;
 
 error: