debugger: wake up the event loop when a debugger command is dispatched

When the event loop was blocked in epoll / kqueue or similar, debugger
commands wouldn't be processed. This patch fixes that by adding an
uv_async handle which is triggered when a debugger command is
dispatched. The async handle's callback makes sure that V8 is entered.

Closes GH-3626
Closes GH-3718

1 files changed, 24 insertions, 0 deletions

diff --git a/src/node.cc b/src/node.cc
index 05208b44b..257b96e9e 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -2471,11 +2471,35 @@ static void ParseArgs(int argc, char **argv) {
 static Isolate* node_isolate = NULL;
 static volatile bool debugger_running = false;
 
+
+static uv_async_t dispatch_debug_messages_async;
+
+
+// Called from the main thread.
+static void DispatchDebugMessagesAsyncCallback(uv_async_t* handle, int status) {
+  v8::Debug::ProcessDebugMessages();
+}
+
+
+// Called from V8 Debug Agent TCP thread.
+static void DispatchMessagesDebugAgentCallback() {
+  uv_async_send(&dispatch_debug_messages_async);
+}
+
+
 static void EnableDebug(bool wait_connect) {
   // If we're called from another thread, make sure to enter the right
   // v8 isolate.
   node_isolate->Enter();
 
+  v8::Debug::SetDebugMessageDispatchHandler(DispatchMessagesDebugAgentCallback,
+                                            false);
+
+  uv_async_init(uv_default_loop(),
+                &dispatch_debug_messages_async,
+                DispatchDebugMessagesAsyncCallback);
+  uv_unref((uv_handle_t*) &dispatch_debug_messages_async);
+
   // Start the debug thread and it's associated TCP server on port 5858.
   bool r = v8::Debug::EnableAgent("node " NODE_VERSION,
                                   debug_port,