Router: fixed segmentation fault.

The router process exited abnormally on reconfiguration if number
of worker threads had been decreased on the previous reconfiguration.
Besides the list of router engines should be updated only after a new
configuration joints have been prepared for all engines.

src/nxt_router.c

@@ -101,8 +101,10 @@ static nxt_int_t nxt_router_thread_create(nxt_task_t *task, nxt_runtime_t *rt,
 static void nxt_router_apps_sort(nxt_router_t *router,
     nxt_router_temp_conf_t *tmcf);
 
-static void nxt_router_engines_post(nxt_router_temp_conf_t *tmcf);
+static void nxt_router_engines_post(nxt_router_t *router,
-static void nxt_router_engine_post(nxt_router_engine_conf_t *recf);
+    nxt_router_temp_conf_t *tmcf);
+static void nxt_router_engine_post(nxt_event_engine_t *engine,
+    nxt_work_t *jobs);
 static void nxt_router_app_data_handler(nxt_task_t *task,
     nxt_port_recv_msg_t *msg);
 
@@ -500,7 +502,7 @@ nxt_router_conf_apply(nxt_task_t *task, void *obj, void *data)
 
     nxt_router_apps_sort(router, tmcf);
 
-    nxt_router_engines_post(tmcf);
+    nxt_router_engines_post(router, tmcf);
 
     nxt_queue_add(&router->sockets, &tmcf->updating);
     nxt_queue_add(&router->sockets, &tmcf->creating);
@@ -1181,9 +1183,11 @@ nxt_router_engines_create(nxt_task_t *task, nxt_router_t *router,
         recf->engine = nxt_queue_link_data(qlk, nxt_event_engine_t, link0);
 
         if (n < threads) {
+            recf->action = NXT_ROUTER_ENGINE_KEEP;
             ret = nxt_router_engine_conf_update(tmcf, recf);
 
         } else {
+            recf->action = NXT_ROUTER_ENGINE_DELETE;
             ret = nxt_router_engine_conf_delete(tmcf, recf);
         }
 
@@ -1202,6 +1206,8 @@ nxt_router_engines_create(nxt_task_t *task, nxt_router_t *router,
             return NXT_ERROR;
         }
 
+        recf->action = NXT_ROUTER_ENGINE_ADD;
+
         recf->engine = nxt_event_engine_create(task, interface, NULL, 0, 0);
         if (nxt_slow_path(recf->engine == NULL)) {
             return NXT_ERROR;
@@ -1212,8 +1218,6 @@ nxt_router_engines_create(nxt_task_t *task, nxt_router_t *router,
             return ret;
         }
 
-        nxt_queue_insert_tail(&router->engines, &recf->engine->link0);
-
         n++;
     }
 
@@ -1533,30 +1537,48 @@ nxt_router_apps_sort(nxt_router_t *router, nxt_router_temp_conf_t *tmcf)
 
 
 static void
-nxt_router_engines_post(nxt_router_temp_conf_t *tmcf)
+nxt_router_engines_post(nxt_router_t *router, nxt_router_temp_conf_t *tmcf)
 {
     nxt_uint_t                n;
+    nxt_event_engine_t        *engine;
     nxt_router_engine_conf_t  *recf;
 
     recf = tmcf->engines->elts;
 
     for (n = tmcf->engines->nelts; n != 0; n--) {
-        nxt_router_engine_post(recf);
+        engine = recf->engine;
+
+        nxt_router_engine_post(engine, recf->jobs);
+
+        switch (recf->action) {
+
+        case NXT_ROUTER_ENGINE_KEEP:
+            break;
+
+        case NXT_ROUTER_ENGINE_ADD:
+            nxt_queue_insert_tail(&router->engines, &engine->link0);
+            break;
+
+        case NXT_ROUTER_ENGINE_DELETE:
+            nxt_queue_remove(&engine->link0);
+            break;
+        }
+
         recf++;
     }
 }
 
 
 static void
-nxt_router_engine_post(nxt_router_engine_conf_t *recf)
+nxt_router_engine_post(nxt_event_engine_t *engine, nxt_work_t *jobs)
 {
     nxt_work_t  *work, *next;
 
-    for (work = recf->jobs; work != NULL; work = next) {
+    for (work = jobs; work != NULL; work = next) {
         next = work->next;
         work->next = NULL;
 
-        nxt_event_engine_post(recf->engine, work);
+        nxt_event_engine_post(engine, work);
     }
 }
 

src/nxt_router.h

@@ -34,6 +34,12 @@ typedef struct {
 typedef struct {
     nxt_event_engine_t     *engine;
     nxt_work_t             *jobs;
+
+    enum {
+        NXT_ROUTER_ENGINE_KEEP = 0,
+        NXT_ROUTER_ENGINE_ADD,
+        NXT_ROUTER_ENGINE_DELETE,
+    }                      action;
 } nxt_router_engine_conf_t;