Work queue thread safety checks for DEBUG build.

src/nxt_port_socket.c

@@ -235,6 +235,7 @@ nxt_port_write_handler(nxt_task_t *task, void *obj, void *data)
     ssize_t                 n;
     nxt_port_t              *port;
     struct iovec            iov[NXT_IOBUF_MAX * 10];
+    nxt_work_queue_t        *wq;
     nxt_queue_link_t        *link;
     nxt_port_method_t       m;
     nxt_port_send_msg_t     *msg;
@@ -301,22 +302,19 @@ nxt_port_write_handler(nxt_task_t *task, void *obj, void *data)
                 goto fail;
             }
 
+            wq = &task->thread->engine->fast_work_queue;
+
             if (msg->buf != plain_buf) {
                 /*
                  * Complete crafted mmap_msgs buf and restore msg->buf
                  * for regular completion call.
                  */
-                nxt_port_mmap_completion(task,
-                                         port->socket.write_work_queue,
-                                         msg->buf);
+                nxt_port_mmap_completion(task, wq, msg->buf);
 
                 msg->buf = plain_buf;
             }
 
-            msg->buf = nxt_sendbuf_completion(task,
-                                              port->socket.write_work_queue,
-                                              msg->buf,
-                                              plain_size);
+            msg->buf = nxt_sendbuf_completion(task, wq, msg->buf, plain_size);
 
             if (msg->buf != NULL) {
                 /*

src/nxt_work_queue.c

@@ -32,6 +32,39 @@ static void nxt_work_queue_allocate(nxt_work_queue_cache_t *cache);
 static nxt_uint_t  nxt_work_queue_bucket_items = 409;
 
 
+#if (NXT_DEBUG)
+
+nxt_inline void
+nxt_work_queue_thread_assert(nxt_work_queue_t *wq)
+{
+    nxt_tid_t     tid;
+    nxt_thread_t  *thread;
+
+    thread = nxt_thread();
+    tid = nxt_thread_tid(thread);
+
+    if (nxt_fast_path(wq->tid == tid)) {
+        return;
+    }
+
+    if (nxt_slow_path(nxt_pid != wq->pid)) {
+        wq->pid = nxt_pid;
+        wq->tid = tid;
+
+        return;
+    }
+
+    nxt_log_alert(thread->log, "work queue locked by thread %PT", wq->tid);
+    nxt_abort();
+}
+
+#else
+
+#define nxt_work_queue_thread_assert(wq)
+
+#endif
+
+
 void
 nxt_work_queue_cache_create(nxt_work_queue_cache_t *cache, size_t chunk_size)
 {
@@ -109,6 +142,8 @@ nxt_work_queue_add(nxt_work_queue_t *wq, nxt_work_handler_t handler,
 {
     nxt_work_t  *work;
 
+    nxt_work_queue_thread_assert(wq);
+
     for ( ;; ) {
         work = wq->cache->next;
 
@@ -144,6 +179,8 @@ nxt_work_queue_pop(nxt_work_queue_t *wq, nxt_task_t **task, void **obj,
 {
     nxt_work_t  *work;
 
+    nxt_work_queue_thread_assert(wq);
+
     work = wq->head;
 
     wq->head = work->next;

src/nxt_work_queue.h

@@ -68,6 +68,8 @@ struct nxt_work_queue_s {
     nxt_work_queue_cache_t      *cache;
 #if (NXT_DEBUG)
     const char                  *name;
+    int32_t                     pid;
+    nxt_tid_t                   tid;
 #endif
 };