Fix: sessiond: bad fd used while rotating exiting app's buffers

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

diff --git a/src/bin/lttng-sessiond/session.c b/src/bin/lttng-sessiond/session.c
index c82bc730962459827046f90f5d9e9d9d594580a4..39edbdf6945d637aa6413b6825377618e262bf9d 100644 (file)
--- a/src/bin/lttng-sessiond/session.c
+++ b/src/bin/lttng-sessiond/session.c
@@ -377,24 +377,45 @@ end:
 
 /*
  * Test if ltt_sessions_ht_by_id/name are empty.
- * Return 1 if empty, 0 if not empty.
+ * Return `false` if hash table objects are null.
  * The session list lock must be held.
  */
-static int ltt_sessions_ht_empty(void)
+static bool ltt_sessions_ht_empty(void)
 {
-       unsigned long count;
+       bool empty = false;
 
        if (!ltt_sessions_ht_by_id) {
-               count = 0;
+               /* The hash tables do not exist yet. */
                goto end;
        }
 
        assert(ltt_sessions_ht_by_name);
 
-       count = lttng_ht_get_count(ltt_sessions_ht_by_id);
-       assert(count == lttng_ht_get_count(ltt_sessions_ht_by_name));
+       if (lttng_ht_get_count(ltt_sessions_ht_by_id) != 0) {
+               /* Not empty.*/
+               goto end;
+       }
+
+       /*
+        * At this point it is expected that the `ltt_sessions_ht_by_name` ht is
+        * empty.
+        *
+        * The removal from both hash tables is done in two different
+        * places:
+        *   - removal from `ltt_sessions_ht_by_name` is done during
+        *     `session_destroy()`
+        *   - removal from `ltt_sessions_ht_by_id` is done later
+        *     in `session_release()` on the last reference put.
+        *
+        * This means that it is possible for `ltt_sessions_ht_by_name` to be
+        * empty but for `ltt_sessions_ht_by_id` to still contain objects when
+        * multiple sessions exists. The reverse is false, hence this sanity
+        * check.
+        */
+       assert(lttng_ht_get_count(ltt_sessions_ht_by_name) == 0);
+       empty = true;
 end:
-       return count ? 0 : 1;
+       return empty;
 }
 
 /*
@@ -1011,6 +1032,7 @@ void session_release(struct urcu_ref *ref)
        lttng_dynamic_array_reset(&session->clear_notifiers);
        free(session->last_archived_chunk_name);
        free(session->base_path);
+       lttng_trigger_put(session->rotate_trigger);
        free(session);
        if (session_published) {
                /*
@@ -1394,6 +1416,7 @@ int session_reset_rotation_state(struct ltt_session *session,
                 */
                session_notify_clear(session);
        }
+
        return ret;
 }