unix: add uv_cancel()

include/uv-private/uv-unix.h

@@ -60,7 +60,7 @@ struct uv__io_s {
 
 struct uv__work {
   void (*work)(struct uv__work *w);
-  void (*done)(struct uv__work *w);
+  void (*done)(struct uv__work *w, int status);
   struct uv_loop_s* loop;
   ngx_queue_t wq;
 };

include/uv.h

@@ -1386,6 +1386,19 @@ struct uv_work_s {
 UV_EXTERN int uv_queue_work(uv_loop_t* loop, uv_work_t* req,
     uv_work_cb work_cb, uv_after_work_cb after_work_cb);
 
+/* Cancel a pending request. Fails if the request is executing or has finished
+ * executing.
+ *
+ * Returns 0 on success, -1 on error. The loop error code is not touched.
+ *
+ * Only cancellation of uv_fs_t, uv_getaddrinfo_t and uv_work_t requests is
+ * currently supported.
+ *
+ * This function is currently only implemented on UNIX platforms. On Windows,
+ * it always returns -1.
+ */
+UV_EXTERN int uv_cancel(uv_req_t* req);
+
 
 struct uv_cpu_info_s {
   char* model;

src/unix/fs.c

@@ -90,7 +90,7 @@
     }                                                                         \
     else {                                                                    \
       uv__fs_work(&(req)->work_req);                                          \
-      uv__fs_done(&(req)->work_req);                                          \
+      uv__fs_done(&(req)->work_req, 0);                                       \
       return (req)->result;                                                   \
     }                                                                         \
   }                                                                           \
@@ -516,12 +516,17 @@ static void uv__fs_work(struct uv__work* w) {
 }
 
 
-static void uv__fs_done(struct uv__work* w) {
+static void uv__fs_done(struct uv__work* w, int status) {
   uv_fs_t* req;
 
   req = container_of(w, uv_fs_t, work_req);
   uv__req_unregister(req->loop, req);
 
+  if (status != 0) {
+    uv_fs_req_cleanup(req);
+    return;
+  }
+
   if (req->errorno != 0) {
     req->errorno = uv_translate_sys_error(req->errorno);
     uv__set_artificial_error(req->loop, req->errorno);

src/unix/getaddrinfo.c

@@ -37,7 +37,7 @@ static void uv__getaddrinfo_work(struct uv__work* w) {
 }
 
 
-static void uv__getaddrinfo_done(struct uv__work* w) {
+static void uv__getaddrinfo_done(struct uv__work* w, int status) {
   uv_getaddrinfo_t* req = container_of(w, uv_getaddrinfo_t, work_req);
   struct addrinfo *res = req->res;
 #if __sun
@@ -63,6 +63,13 @@ static void uv__getaddrinfo_done(struct uv__work* w) {
   else
     assert(0);
 
+  req->hints = NULL;
+  req->service = NULL;
+  req->hostname = NULL;
+
+  if (status != 0)
+    return;
+
   if (req->retcode == 0) {
     /* OK */
 #if EAI_NODATA /* FreeBSD deprecated EAI_NODATA */

src/unix/internal.h

@@ -174,7 +174,7 @@ void uv__signal_loop_cleanup();
 void uv__work_submit(uv_loop_t* loop,
                      struct uv__work *w,
                      void (*work)(struct uv__work *w),
-                     void (*done)(struct uv__work *w));
+                     void (*done)(struct uv__work *w, int status));
 void uv__work_done(uv_async_t* handle, int status);
 
 /* platform specific */

src/unix/threadpool.c

@@ -30,6 +30,9 @@ static ngx_queue_t wq;
 static volatile int initialized;
 
 
+/* To avoid deadlock with uv_cancel() it's crucial that the worker
+ * never holds the global mutex and the loop-local mutex at the same time.
+ */
 static void worker(void* arg) {
   struct uv__work* w;
   ngx_queue_t* q;
@@ -46,8 +49,11 @@ static void worker(void* arg) {
 
     if (q == &exit_message)
       uv_cond_signal(&cond);
-    else
+    else {
       ngx_queue_remove(q);
+      ngx_queue_init(q);  /* Signal uv_cancel() that the work req is
+                             executing. */
+    }
 
     uv_mutex_unlock(&mutex);
 
@@ -58,6 +64,8 @@ static void worker(void* arg) {
     w->work(w);
 
     uv_mutex_lock(&w->loop->wq_mutex);
+    w->work = NULL;  /* Signal uv_cancel() that the work req is done
+                        executing. */
     ngx_queue_insert_tail(&w->loop->wq, &w->wq);
     uv_async_send(&w->loop->wq_async);
     uv_mutex_unlock(&w->loop->wq_mutex);
@@ -116,7 +124,7 @@ static void cleanup(void) {
 void uv__work_submit(uv_loop_t* loop,
                      struct uv__work* w,
                      void (*work)(struct uv__work* w),
-                     void (*done)(struct uv__work* w)) {
+                     void (*done)(struct uv__work* w, int status)) {
   uv_once(&once, init_once);
   w->loop = loop;
   w->work = work;
@@ -125,6 +133,29 @@ void uv__work_submit(uv_loop_t* loop,
 }
 
 
+int uv__work_cancel(uv_loop_t* loop, uv_req_t* req, struct uv__work* w) {
+  int cancelled;
+
+  uv_mutex_lock(&mutex);
+  uv_mutex_lock(&w->loop->wq_mutex);
+
+  cancelled = !ngx_queue_empty(&w->wq) && w->work != NULL;
+  if (cancelled)
+    ngx_queue_remove(&w->wq);
+
+  uv_mutex_unlock(&w->loop->wq_mutex);
+  uv_mutex_unlock(&mutex);
+
+  if (!cancelled)
+    return -1;
+
+  ngx_queue_init(&w->wq);
+  w->done(w, -UV_ECANCELED);
+
+  return 0;
+}
+
+
 void uv__work_done(uv_async_t* handle, int status) {
   struct uv__work* w;
   uv_loop_t* loop;
@@ -146,7 +177,7 @@ void uv__work_done(uv_async_t* handle, int status) {
     ngx_queue_remove(q);
 
     w = container_of(q, struct uv__work, wq);
-    w->done(w);
+    w->done(w, 0);
   }
 }
 
@@ -158,11 +189,14 @@ static void uv__queue_work(struct uv__work* w) {
 }
 
 
-static void uv__queue_done(struct uv__work* w) {
+static void uv__queue_done(struct uv__work* w, int status) {
   uv_work_t* req = container_of(w, uv_work_t, work_req);
 
   uv__req_unregister(req->loop, req);
 
+  if (status != 0)
+    return;
+
   if (req->after_work_cb)
     req->after_work_cb(req);
 }
@@ -182,3 +216,28 @@ int uv_queue_work(uv_loop_t* loop,
   uv__work_submit(loop, &req->work_req, uv__queue_work, uv__queue_done);
   return 0;
 }
+
+
+int uv_cancel(uv_req_t* req) {
+  struct uv__work* wreq;
+  uv_loop_t* loop;
+
+  switch (req->type) {
+  case UV_FS:
+    loop =  ((uv_fs_t*) req)->loop;
+    wreq = &((uv_fs_t*) req)->work_req;
+    break;
+  case UV_GETADDRINFO:
+    loop =  ((uv_getaddrinfo_t*) req)->loop;
+    wreq = &((uv_getaddrinfo_t*) req)->work_req;
+    break;
+  case UV_WORK:
+    loop =  ((uv_work_t*) req)->loop;
+    wreq = &((uv_work_t*) req)->work_req;
+    break;
+  default:
+    return -1;
+  }
+
+  return uv__work_cancel(loop, req, wreq);
+}

src/win/threadpool.c

@@ -70,6 +70,11 @@ int uv_queue_work(uv_loop_t* loop, uv_work_t* req, uv_work_cb work_cb,
 }
 
 
+int uv_cancel(uv_req_t* req) {
+  return -1;
+}
+
+
 void uv_process_work_req(uv_loop_t* loop, uv_work_t* req) {
   uv__req_unregister(loop, req);
   if(req->after_work_cb)

test/test-list.h

@@ -187,6 +187,9 @@ TEST_DECLARE   (fs_rename_to_existing_file)
 TEST_DECLARE   (threadpool_queue_work_simple)
 TEST_DECLARE   (threadpool_queue_work_einval)
 TEST_DECLARE   (threadpool_multiple_event_loops)
+TEST_DECLARE   (threadpool_cancel_getaddrinfo)
+TEST_DECLARE   (threadpool_cancel_work)
+TEST_DECLARE   (threadpool_cancel_fs)
 TEST_DECLARE   (thread_mutex)
 TEST_DECLARE   (thread_rwlock)
 TEST_DECLARE   (thread_create)
@@ -454,6 +457,9 @@ TASK_LIST_START
   TEST_ENTRY  (threadpool_queue_work_simple)
   TEST_ENTRY  (threadpool_queue_work_einval)
   TEST_ENTRY  (threadpool_multiple_event_loops)
+  TEST_ENTRY  (threadpool_cancel_getaddrinfo)
+  TEST_ENTRY  (threadpool_cancel_work)
+  TEST_ENTRY  (threadpool_cancel_fs)
   TEST_ENTRY  (thread_mutex)
   TEST_ENTRY  (thread_rwlock)
   TEST_ENTRY  (thread_create)