Fix: check ht_del ret value of ust app session

UST app sesion can be destroyed by two execution paths. Either the app
unregisters or a destroy session is triggered. So, allowing a ht_del to
fail means that the session is already scheduled for teardown in a rcu
call.

Furthermore, this means that when looking up for a ust app session that
is not found becomes valid since it means it is in the teardown process.

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

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index c81f6e8f5597e1531292cfee2e4f5b5f57faf0dd..ec6f998bb7a87e6a6d2cc957a26cf753381c3c66 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -269,7 +269,10 @@ void delete_ust_app(struct ust_app *app)
        cds_lfht_for_each_entry(app->sessions->ht, &iter.iter, ua_sess,
                        node.node) {
                ret = lttng_ht_del(app->sessions, &iter);
-               assert(!ret);
+               if (ret) {
+                       /* The session is already scheduled for teardown. */
+                       continue;
+               }
                delete_ust_app_session(app->sock, ua_sess);
        }
        lttng_ht_destroy(app->sessions);
@@ -1964,8 +1967,10 @@ int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
                        continue;
                }
                ua_sess = lookup_session_by_app(usess, app);
-               /* If ua_sess is NULL, there is a code flow error */
-               assert(ua_sess);
+               if (!ua_sess) {
+                       /* The application has problem or is probably dead. */
+                       continue;
+               }
 
                /* Lookup channel in the ust app session */
                lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
@@ -2087,8 +2092,10 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
                        continue;
                }
                ua_sess = lookup_session_by_app(usess, app);
-               /* If ua_sess is NULL, there is a code flow error */
-               assert(ua_sess);
+               if (!ua_sess) {
+                       /* The application has problem or is probably dead. */
+                       continue;
+               }
 
                /* Lookup channel in the ust app session */
                lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
@@ -2147,8 +2154,10 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
                        continue;
                }
                ua_sess = lookup_session_by_app(usess, app);
-               /* If ua_sess is NULL, there is a code flow error */
-               assert(ua_sess);
+               if (!ua_sess) {
+                       /* The application has problem or is probably dead. */
+                       continue;
+               }
 
                /* Lookup channel in the ust app session */
                lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
@@ -2442,7 +2451,11 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
        }
        ua_sess = caa_container_of(node, struct ust_app_session, node);
        ret = lttng_ht_del(app->sessions, &iter);
-       assert(!ret);
+       if (ret) {
+               /* Already scheduled for teardown. */
+               goto end;
+       }
+
        obj.handle = ua_sess->handle;
        obj.shm_fd = -1;
        obj.wait_fd = -1;
@@ -2716,8 +2729,10 @@ int ust_app_enable_event_pid(struct ltt_ust_session *usess,
        }
 
        ua_sess = lookup_session_by_app(usess, app);
-       /* If ua_sess is NULL, there is a code flow error */
-       assert(ua_sess);
+       if (!ua_sess) {
+               /* The application has problem or is probably dead. */
+               goto error;
+       }
 
        /* Lookup channel in the ust app session */
        lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);
@@ -2777,8 +2792,10 @@ int ust_app_disable_event_pid(struct ltt_ust_session *usess,
        }
 
        ua_sess = lookup_session_by_app(usess, app);
-       /* If ua_sess is NULL, there is a code flow error */
-       assert(ua_sess);
+       if (!ua_sess) {
+               /* The application has problem or is probably dead. */
+               goto error;
+       }
 
        /* Lookup channel in the ust app session */
        lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);