Fix: sessiond: previously created channel cannot be enabled

[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index 31eb2b43025f6d0207ed3e840c634dabc25b405a..5868c829f689d7015fc839ff8048197e182b5ea0 100644 (file)
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -517,7 +517,6 @@ static int list_lttng_agent_events(struct agent *agt,
 
        rcu_read_lock();
        nb_event = lttng_ht_get_count(agt->events);
-       rcu_read_unlock();
        if (nb_event == 0) {
                ret = nb_event;
                *total_size = 0;
@@ -531,7 +530,6 @@ static int list_lttng_agent_events(struct agent *agt,
         * This is only valid because the commands which add events are
         * processed in the same thread as the listing.
         */
-       rcu_read_lock();
        cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
                ret = increment_extended_len(event->filter_expression, NULL, NULL,
                                &extended_len);
@@ -541,7 +539,6 @@ static int list_lttng_agent_events(struct agent *agt,
                        goto error;
                }
        }
-       rcu_read_unlock();
 
        *total_size = nb_event * sizeof(*tmp_events) + extended_len;
        tmp_events = zmalloc(*total_size);
@@ -554,7 +551,6 @@ static int list_lttng_agent_events(struct agent *agt,
        extended_at = ((uint8_t *) tmp_events) +
                nb_event * sizeof(struct lttng_event);
 
-       rcu_read_lock();
        cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
                strncpy(tmp_events[i].name, event->name, sizeof(tmp_events[i].name));
                tmp_events[i].name[sizeof(tmp_events[i].name) - 1] = '\0';
@@ -1511,15 +1507,6 @@ int cmd_enable_channel(struct ltt_session *session,
 
        rcu_read_lock();
 
-       /*
-        * 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->has_been_started) {
-               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
-               goto error;
-       }
-
        /*
         * If the session is a live session, remove the switch timer, the
         * live timer does the same thing but sends also synchronisation
@@ -1568,6 +1555,15 @@ int cmd_enable_channel(struct ltt_session *session,
                kchan = trace_kernel_get_channel_by_name(attr.name,
                                session->kernel_session);
                if (kchan == NULL) {
+                       /*
+                        * Don't try to create a channel if the session has been started at
+                        * some point in time before. The tracer does not allow it.
+                        */
+                       if (session->has_been_started) {
+                               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+                               goto error;
+                       }
+
                        if (session->snapshot.nb_output > 0 ||
                                        session->snapshot_mode) {
                                /* Enforce mmap output for snapshot sessions. */
@@ -1627,6 +1623,15 @@ int cmd_enable_channel(struct ltt_session *session,
 
                uchan = trace_ust_find_channel_by_name(chan_ht, attr.name);
                if (uchan == NULL) {
+                       /*
+                        * Don't try to create a channel if the session has been started at
+                        * some point in time before. The tracer does not allow it.
+                        */
+                       if (session->has_been_started) {
+                               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+                               goto error;
+                       }
+
                        ret = channel_ust_create(usess, &attr, domain->buf_type);
                        if (attr.name[0] != '\0') {
                                usess->has_non_default_channel = 1;