inspector: libuv notification on incoming message

Currently Inspector posts a V8 "task" when a message is incoming. To
make sure messages are processed even when no JS is executed (e.g. while
waiting for I/O or timer), inspector will now post a libuv request.

Fixes: https://github.com/nodejs/node/issues/11589
PR-URL: https://github.com/nodejs/node/pull/11617
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

src/inspector_agent.cc

@@ -159,6 +159,7 @@ class AgentImpl {
 
   static void ThreadCbIO(void* agent);
   static void WriteCbIO(uv_async_t* async);
+  static void MainThreadAsyncCb(uv_async_t* req);
 
   void InstallInspectorOnProcess();
 
@@ -190,6 +191,7 @@ class AgentImpl {
   node::Environment* parent_env_;
 
   uv_async_t io_thread_req_;
+  uv_async_t main_thread_req_;
   V8NodeInspector* inspector_;
   v8::Platform* platform_;
   MessageQueue<InspectorAction> incoming_message_queue_;
@@ -334,6 +336,9 @@ AgentImpl::AgentImpl(Environment* env) : delegate_(nullptr),
                                          dispatching_messages_(false),
                                          session_id_(0),
                                          server_(nullptr) {
+  CHECK_EQ(0, uv_async_init(env->event_loop(), &main_thread_req_,
+                            AgentImpl::MainThreadAsyncCb));
+  uv_unref(reinterpret_cast<uv_handle_t*>(&main_thread_req_));
   CHECK_EQ(0, uv_sem_init(&start_sem_, 0));
   memset(&io_thread_req_, 0, sizeof(io_thread_req_));
 }
@@ -416,10 +421,7 @@ bool AgentImpl::Start(v8::Platform* platform, const char* path,
 
   InstallInspectorOnProcess();
 
-  int err = uv_loop_init(&child_loop_);
-  CHECK_EQ(err, 0);
-
-  err = uv_thread_create(&thread_, AgentImpl::ThreadCbIO, this);
+  int err = uv_thread_create(&thread_, AgentImpl::ThreadCbIO, this);
   CHECK_EQ(err, 0);
   uv_sem_wait(&start_sem_);
 
@@ -606,6 +608,7 @@ void AgentImpl::PostIncomingMessage(InspectorAction action, int session_id,
     platform_->CallOnForegroundThread(isolate,
                                       new DispatchOnInspectorBackendTask(this));
     isolate->RequestInterrupt(InterruptCallback, this);
+    CHECK_EQ(0, uv_async_send(&main_thread_req_));
   }
   NotifyMessageReceived();
 }
@@ -662,6 +665,12 @@ void AgentImpl::DispatchMessages() {
   dispatching_messages_ = false;
 }
 
+// static
+void AgentImpl::MainThreadAsyncCb(uv_async_t* req) {
+  AgentImpl* agent = node::ContainerOf(&AgentImpl::main_thread_req_, req);
+  agent->DispatchMessages();
+}
+
 void AgentImpl::Write(TransportAction action, int session_id,
                       const StringView& inspector_message) {
   AppendMessage(&outgoing_message_queue_, action, session_id,

test/inspector/inspector-helper.js

@@ -427,9 +427,24 @@ Harness.prototype.expectShutDown = function(errorCode) {
   });
 };
 
-exports.startNodeForInspectorTest = function(callback) {
-  const child = spawn(process.execPath,
-      [ '--inspect-brk', mainScript ]);
+Harness.prototype.kill = function() {
+  return this.enqueue_((callback) => {
+    this.process_.kill();
+    callback();
+  });
+};
+
+exports.startNodeForInspectorTest = function(callback,
+                                             inspectorFlag = '--inspect-brk',
+                                             opt_script_contents) {
+  const args = [inspectorFlag];
+  if (opt_script_contents) {
+    args.push('-e', opt_script_contents);
+  } else {
+    args.push(mainScript);
+  }
+
+  const child = spawn(process.execPath, args);
 
   const timeoutId = timeout('Child process did not start properly', 4);
 

test/inspector/test-not-blocked-on-idle.js

@@ -0,0 +1,20 @@
+'use strict';
+require('../common');
+const helper = require('./inspector-helper.js');
+
+function shouldShutDown(session) {
+  session
+    .sendInspectorCommands([
+        { 'method': 'Debugger.enable' },
+        { 'method': 'Debugger.pause' },
+    ])
+    .disconnect(true);
+}
+
+function runTests(harness) {
+  // 1 second wait to make sure the inferior began running the script
+  setTimeout(() => harness.runFrontendSession([shouldShutDown]).kill(), 1000);
+}
+
+const script = 'setInterval(() => {debugger;}, 60000);';
+helper.startNodeForInspectorTest(runTests, '--inspect', script);