From 1b197d0bb2ae72d2d81c6d38acf1c008a5e74c75 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 22 Aug 2022 17:01:41 -0400
Subject: [PATCH] Resolve crash of machines that require the ROM requester.

---
 Concurrency/AsyncTaskQueue.hpp                | 63 +++++++++++--------
 .../Mac/Clock Signal/Machine/CSMachine.mm     |  5 +-
 2 files changed, 41 insertions(+), 27 deletions(-)

diff --git a/Concurrency/AsyncTaskQueue.hpp b/Concurrency/AsyncTaskQueue.hpp
index 7a8452734..f0de9f640 100644
--- a/Concurrency/AsyncTaskQueue.hpp
+++ b/Concurrency/AsyncTaskQueue.hpp
@@ -65,34 +65,14 @@ template <> struct TaskQueueStorage<void> {
 	action occupies the asynchronous thread for long enough. So it is not true that @c perform will be
 	called once per action.
 */
-template <bool perform_automatically, typename Performer = void> class AsyncTaskQueue: public TaskQueueStorage<Performer> {
+template <bool perform_automatically, bool start_immediately = true, typename Performer = void> class AsyncTaskQueue: public TaskQueueStorage<Performer> {
 	public:
 		template <typename... Args> AsyncTaskQueue(Args&&... args) :
-			TaskQueueStorage<Performer>(std::forward<Args>(args)...),
-			thread_{
-				[this] {
-					ActionVector actions;
-
-					while(!should_quit_) {
-						// Wait for new actions to be signalled, and grab them.
-						std::unique_lock lock(condition_mutex_);
-						while(actions_.empty()) {
-							condition_.wait(lock);
-						}
-						std::swap(actions, actions_);
-						lock.unlock();
-
-						// Update to now (which is possibly a no-op).
-						TaskQueueStorage<Performer>::update();
-
-						// Perform the actions and destroy them.
-						for(const auto &action: actions) {
-							action();
-						}
-						actions.clear();
-					}
-				}
-			} {}
+			TaskQueueStorage<Performer>(std::forward<Args>(args)...) {
+			if constexpr (start_immediately) {
+				start();
+			}
+		}
 
 		/// Enqueus @c post_action to be performed asynchronously at some point
 		/// in the future. If @c perform_automatically is @c true then the action
@@ -136,6 +116,37 @@ template <bool perform_automatically, typename Performer = void> class AsyncTask
 			}
 		}
 
+		/// Starts the queue if it has never been started before.
+		///
+		/// This is not guaranteed safely to restart a stopped queue.
+		void start() {
+			thread_ = std::move(std::thread{
+				[this] {
+					ActionVector actions;
+
+					// Continue until told to quit.
+					while(!should_quit_) {
+						// Wait for new actions to be signalled, and grab them.
+						std::unique_lock lock(condition_mutex_);
+						while(actions_.empty()) {
+							condition_.wait(lock);
+						}
+						std::swap(actions, actions_);
+						lock.unlock();
+
+						// Update to now (which is possibly a no-op).
+						TaskQueueStorage<Performer>::update();
+
+						// Perform the actions and destroy them.
+						for(const auto &action: actions) {
+							action();
+						}
+						actions.clear();
+					}
+				}
+			});
+		}
+
 		/// Schedules any remaining unscheduled work, then blocks synchronously
 		/// until all scheduled work has been performed.
 		void flush() {
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm
index c3912a080..3ad335c17 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
@@ -122,7 +122,7 @@ struct ActivityObserver: public Activity::Observer {
 	CSJoystickManager *_joystickManager;
 	NSMutableArray<CSMachineLED *> *_leds;
 
-	Concurrency::AsyncTaskQueue<true, MachineUpdater> updater;
+	Concurrency::AsyncTaskQueue<true, false, MachineUpdater> updater;
 	Time::ScanSynchroniser _scanSynchroniser;
 
 	NSTimer *_joystickTimer;
@@ -149,6 +149,9 @@ struct ActivityObserver: public Activity::Observer {
 			return nil;
 		}
 		updater.performer.machine = _machine->timed_machine();
+		if(updater.performer.machine) {
+			updater.start();
+		}
 
 		// Use the keyboard as a joystick if the machine has no keyboard, or if it has a 'non-exclusive' keyboard.
 		_inputMode =