From: David Goulet <dgoulet@efficios.com>
Date: Thu, 12 Jan 2012 18:04:51 +0000 (-0500)
Subject: Fix out of order channel insert in hash table
X-Git-Tag: v2.0-pre17~23
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=58f3ca76ddd0d871fc1b71d816bdbabe1d7adeb1

Fix out of order channel insert in hash table

The channel, ust-app side, was added to the hash table of the session
even if the creation failed on the tracer side. When enabling event for
that channel, a segfault was hit since the channel did not exist on the
tracer side and channel_data was NULL at this point.

Now the channel insertion in the hash table is done *after* enabling it
on the tracer side.

Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/lttng-sessiond/channel.c b/lttng-sessiond/channel.c
index b4dc48d16..3dc04ccb8 100644
--- a/lttng-sessiond/channel.c
+++ b/lttng-sessiond/channel.c
@@ -236,11 +236,16 @@ int channel_ust_create(struct ltt_ust_session *usess, int domain,
 		ret = LTTCOMM_FATAL;
 		goto error;
 	}
+	uchan->enabled = 1;
 
 	switch (domain) {
 	case LTTNG_DOMAIN_UST:
 		DBG2("Channel %s being created in UST global domain", uchan->name);
-		chan_ht = usess->domain_global.channels;
+
+		/* Adding the channel to the channel hash table. */
+		rcu_read_lock();
+		lttng_ht_add_unique_str(usess->domain_global.channels, &uchan->node);
+		rcu_read_unlock();
 
 		/* Enable channel for global domain */
 		ret = ust_app_create_channel_glb(usess, uchan);
@@ -258,8 +263,6 @@ int channel_ust_create(struct ltt_ust_session *usess, int domain,
 		goto error_free_chan;
 	}
 
-	uchan->enabled = 1;
-	lttng_ht_add_unique_str(chan_ht, &uchan->node);
 	DBG2("Channel %s created successfully", uchan->name);
 
 	free(defattr);
diff --git a/lttng-sessiond/ust-app.c b/lttng-sessiond/ust-app.c
index 9c500481e..4f68a87ee 100644
--- a/lttng-sessiond/ust-app.c
+++ b/lttng-sessiond/ust-app.c
@@ -584,7 +584,7 @@ static int create_ust_channel(struct ust_app *app,
 	ret = ustctl_create_channel(app->key.sock, ua_sess->handle,
 			(struct lttng_ust_channel_attr *)&ua_chan->attr, &ua_chan->obj);
 	if (ret < 0) {
-		DBG("Error creating channel %s for app (pid: %d, sock: %d) "
+		ERR("Creating channel %s for app (pid: %d, sock: %d) "
 				"and session handle %d with ret %d",
 				ua_chan->name, app->key.pid, app->key.sock,
 				ua_sess->handle, ret);
@@ -1062,8 +1062,6 @@ static struct ust_app_channel *create_ust_app_channel(
 			goto error;
 		}
 		shadow_copy_channel(ua_chan, uchan);
-
-		lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
 	} else {
 		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
 	}
@@ -1073,6 +1071,8 @@ static struct ust_app_channel *create_ust_app_channel(
 		goto error;
 	}
 
+	lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
+
 	return ua_chan;
 
 error: