Router: fixing assertion on app thread port handle.

A new application thread port message can be processed in the router after the
application is removed from the router.  Assertion for this case is replaced by
a condition to store the new thread port until receiving the stop notification
from the application process.

2 files changed, 17 insertions, 8 deletions

diff --git a/docs/changes.xml b/docs/changes.xml
index 5265d529..dd8fb731 100644
--- a/docs/changes.xml
+++ b/docs/changes.xml
@@ -46,6 +46,13 @@ with TLS certificate configured; the bug had appeared in 1.23.0.
 
 <change type="bugfix">
 <para>
+the router process could crash on rapid mutithreaded application
+reconfiguration.
+</para>
+</change>
+
+<change type="bugfix">
+<para>
 a descriptor and memory leak occurred in the router process when an app
 process stopped or crashed.
 </para>
diff --git a/src/nxt_router.c b/src/nxt_router.c
index 26b846b0..409f88a1 100644
--- a/src/nxt_router.c
+++ b/src/nxt_router.c
@@ -680,18 +680,20 @@ nxt_router_new_port_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
     nxt_assert(main_app_port != NULL);
 
     app = main_app_port->app;
-    nxt_assert(app != NULL);
 
-    nxt_thread_mutex_lock(&app->mutex);
+    if (nxt_fast_path(app != NULL)) {
+        nxt_thread_mutex_lock(&app->mutex);
 
-    /* TODO here should be find-and-add code because there can be
-       port waiters in port_hash */
-    nxt_port_hash_add(&app->port_hash, port);
-    app->port_hash_count++;
+        /* TODO here should be find-and-add code because there can be
+           port waiters in port_hash */
+        nxt_port_hash_add(&app->port_hash, port);
+        app->port_hash_count++;
 
-    nxt_thread_mutex_unlock(&app->mutex);
+        nxt_thread_mutex_unlock(&app->mutex);
+
+        port->app = app;
+    }
 
-    port->app = app;
     port->main_app_port = main_app_port;
 
     nxt_port_socket_write(task, port, NXT_PORT_MSG_PORT_ACK, -1, 0, 0, NULL);