From: David Goulet <dgoulet@efficios.com>
Date: Tue, 25 Jun 2013 18:15:41 +0000 (-0400)
Subject: Fix: don't enable a channel if a session was already started
X-Git-Tag: v2.2.0~4
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=d2f11c4a439e76804369810907e2a22dfcd0956f;p=lttng-tools.git

Fix: don't enable a channel if a session was already started

This removes also the check done to start the session if it was started
before.

Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/doc/man/lttng.1 b/doc/man/lttng.1
index e650d2426..72454f0d3 100644
--- a/doc/man/lttng.1
+++ b/doc/man/lttng.1
@@ -312,8 +312,8 @@ It is important to note that if a certain type of buffers is used, the session
 will be set with that type and all other subsequent channel needs to have the
 same type.
 
-For the kernel tracer (\-k), once the session is started at least once, it's
-not possible anymore to enable new channel for that session.
+Note that once the session has been started and enabled on the tracer side,
+it's not possible anymore to enable a new channel for that session.
 .fi
 
 .B OPTIONS:
diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index a23a2b761..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:
@@ -1616,8 +1602,6 @@ int cmd_stop_trace(struct ltt_session *session)
 		}
 	}
 
-	session->started = 0;
-
 	ret = LTTNG_OK;
 
 error: