src: make implementing CancelPendingDelayedTasks for platform optional

Fold `CancelPendingDelayedTasks()` into `UnregisterIsolate()` and
make implementing it optional.

It makes sense for these two operations to happen at the same time,
so it is sufficient to provide a single operation instead of two
separate ones.

PR-URL: https://github.com/nodejs/node/pull/30034
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Shelley Vohr <codebytere@gmail.com>

1 files changed, 26 insertions, 18 deletions

diff --git a/src/node_platform.cc b/src/node_platform.cc
index f726382171..6e3b4abfee 100644
--- a/src/node_platform.cc
+++ b/src/node_platform.cc
@@ -285,22 +285,33 @@ void PerIsolatePlatformData::Shutdown() {
   // effectively deleting the tasks instead of running them.
   foreground_delayed_tasks_.PopAll();
   foreground_tasks_.PopAll();
+  scheduled_delayed_tasks_.clear();
 
-  CancelPendingDelayedTasks();
-
-  ShutdownCbList* copy = new ShutdownCbList(std::move(shutdown_callbacks_));
-  flush_tasks_->data = copy;
+  // Both destroying the scheduled_delayed_tasks_ lists and closing
+  // flush_tasks_ handle add tasks to the event loop. We keep a count of all
+  // non-closed handles, and when that reaches zero, we inform any shutdown
+  // callbacks that the platform is done as far as this Isolate is concerned.
+  self_reference_ = shared_from_this();
   uv_close(reinterpret_cast<uv_handle_t*>(flush_tasks_),
            [](uv_handle_t* handle) {
-    std::unique_ptr<ShutdownCbList> callbacks(
-        static_cast<ShutdownCbList*>(handle->data));
-    for (const auto& callback : *callbacks)
-      callback.cb(callback.data);
-    delete reinterpret_cast<uv_async_t*>(handle);
+    std::unique_ptr<uv_async_t> flush_tasks {
+        reinterpret_cast<uv_async_t*>(handle) };
+    PerIsolatePlatformData* platform_data =
+        static_cast<PerIsolatePlatformData*>(flush_tasks->data);
+    platform_data->DecreaseHandleCount();
+    platform_data->self_reference_.reset();
   });
   flush_tasks_ = nullptr;
 }
 
+void PerIsolatePlatformData::DecreaseHandleCount() {
+  CHECK_GE(uv_handle_count_, 1);
+  if (--uv_handle_count_ == 0) {
+    for (const auto& callback : shutdown_callbacks_)
+      callback.cb(callback.data);
+  }
+}
+
 NodePlatform::NodePlatform(int thread_pool_size,
                            TracingController* tracing_controller) {
   if (tracing_controller) {
@@ -382,10 +393,6 @@ void PerIsolatePlatformData::RunForegroundTask(uv_timer_t* handle) {
   delayed->platform_data->DeleteFromScheduledTasks(delayed);
 }
 
-void PerIsolatePlatformData::CancelPendingDelayedTasks() {
-  scheduled_delayed_tasks_.clear();
-}
-
 void NodePlatform::DrainTasks(Isolate* isolate) {
   std::shared_ptr<PerIsolatePlatformData> per_isolate = ForIsolate(isolate);
 
@@ -409,12 +416,15 @@ bool PerIsolatePlatformData::FlushForegroundTasksInternal() {
     // the delay is non-zero. This should not be a problem in practice.
     uv_timer_start(&delayed->timer, RunForegroundTask, delay_millis, 0);
     uv_unref(reinterpret_cast<uv_handle_t*>(&delayed->timer));
+    uv_handle_count_++;
 
     scheduled_delayed_tasks_.emplace_back(delayed.release(),
                                           [](DelayedTask* delayed) {
       uv_close(reinterpret_cast<uv_handle_t*>(&delayed->timer),
                [](uv_handle_t* handle) {
-        delete static_cast<DelayedTask*>(handle->data);
+        std::unique_ptr<DelayedTask> task {
+            static_cast<DelayedTask*>(handle->data) };
+        task->platform_data->DecreaseHandleCount();
       });
     });
   }
@@ -454,10 +464,6 @@ bool NodePlatform::FlushForegroundTasks(Isolate* isolate) {
   return ForIsolate(isolate)->FlushForegroundTasksInternal();
 }
 
-void NodePlatform::CancelPendingDelayedTasks(Isolate* isolate) {
-  ForIsolate(isolate)->CancelPendingDelayedTasks();
-}
-
 bool NodePlatform::IdleTasksEnabled(Isolate* isolate) { return false; }
 
 std::shared_ptr<v8::TaskRunner>
@@ -548,4 +554,6 @@ std::queue<std::unique_ptr<T>> TaskQueue<T>::PopAll() {
   return result;
 }
 
+void MultiIsolatePlatform::CancelPendingDelayedTasks(Isolate* isolate) {}
+
 }  // namespace node