Core: Make RunOnCPUThread always non-blocking.

Source/Core/Core/Core.cpp

@@ -825,8 +825,7 @@ static void RestoreStateAndUnlock(Core::System& system, const bool unpause_on_un
   system.GetCPU().RestoreStateAndUnlock(unpause_on_unlock);
 }
 
-void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> function,
+void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> function)
-                    bool wait_for_completion)
 {
   if (IsCPUThread())
   {
@@ -834,8 +833,6 @@ void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> funct
     return;
   }
 
-  Common::OneShotEvent cpu_thread_job_finished;
-
   // Pause the CPU (set it to stepping mode).
   const bool was_running = PauseAndLock(system);
 
@@ -843,15 +840,6 @@ void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> funct
   {
     // If the core hasn't been started, there is no active CPU thread we can race against.
     function();
-    wait_for_completion = false;
-  }
-  else if (wait_for_completion)
-  {
-    // Queue the job function followed by triggering the event.
-    system.GetCPU().AddCPUThreadJob([&function, &cpu_thread_job_finished] {
-      function();
-      cpu_thread_job_finished.Set();
-    });
   }
   else
   {
@@ -861,14 +849,6 @@ void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> funct
 
   // Release the CPU thread, and let it execute the callback.
   RestoreStateAndUnlock(system, was_running);
-
-  // If we're waiting for completion, block until the event fires.
-  if (wait_for_completion)
-  {
-    // Periodically yield to the UI thread, so we don't deadlock.
-    while (!cpu_thread_job_finished.WaitFor(std::chrono::milliseconds(10)))
-      Host_YieldToUI();
-  }
 }
 
 // --- Callbacks for backends / engine ---

Source/Core/Core/Core.h

@@ -158,8 +158,7 @@ void FrameUpdateOnCPUThread();
 void OnFrameEnd(Core::System& system);
 
 // Run a function on the CPU thread, asynchronously.
-void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> function,
+void RunOnCPUThread(Core::System& system, Common::MoveOnlyFunction<void()> function);
-                    bool wait_for_completion);
 
 // for calling back into UI code without introducing a dependency on it in core
 using StateChangedCallbackFunc = std::function<void(Core::State)>;

Source/Core/Core/State.cpp

@@ -496,11 +496,9 @@ static void SaveAsFromCore(Core::System& system, std::string filename)
 void SaveAs(Core::System& system, std::string filename)
 {
   Core::RunOnCPUThread(
-      system,
+      system, [&system, filename = std::move(filename), lock = GetStateSaveTaskLock()]() mutable {
-      [&system, filename = std::move(filename), lock = GetStateSaveTaskLock()]() mutable {
         SaveAsFromCore(system, std::move(filename));
-      },
+      });
-      false);
 }
 
 static bool GetVersionFromLZO(StateHeader& header, File::IOFile& f)
@@ -873,12 +871,9 @@ void LoadAs(Core::System& system, std::string filename)
   if (!CheckIfStateLoadIsAllowed(system))
     return;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(system, [&system, filename = std::move(filename)]() mutable {
-      system,
-      [&system, filename = std::move(filename)]() mutable {
     LoadAsFromCore(system, std::move(filename));
-      },
+  });
-      false);
 }
 
 void SetOnAfterLoadCallback(AfterLoadCallbackFunc callback)
@@ -919,9 +914,7 @@ void LoadLastSaved(Core::System& system, int i)
   if (!CheckIfStateLoadIsAllowed(system))
     return;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(system, [&system, i] {
-      system,
-      [&system, i] {
     // Data must reach the filesystem for up to date "UsedSlots".
     s_compress_and_dump_thread.WaitForCompletion();
 
@@ -934,15 +927,12 @@ void LoadLastSaved(Core::System& system, int i)
 
     std::ranges::stable_sort(used_slots, std::ranges::greater{}, &SlotWithTimestamp::timestamp);
     LoadAsFromCore(system, MakeStateFilename(used_slots[i].slot));
-      },
+  });
-      false);
 }
 
 void SaveFirstSaved(Core::System& system)
 {
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(system, [&system, lock = GetStateSaveTaskLock()] {
-      system,
-      [&system, lock = GetStateSaveTaskLock()] {
     // Data must reach the filesystem for up to date "UsedSlots".
     s_compress_and_dump_thread.WaitForCompletion();
 
@@ -956,8 +946,7 @@ void SaveFirstSaved(Core::System& system)
     }
 
     SaveAsFromCore(system, MakeStateFilename(*slot));
-      },
+  });
-      false);
 }
 
 // Load the last state before loading the state
@@ -966,9 +955,7 @@ void UndoLoadState(Core::System& system)
   if (!CheckIfStateLoadIsAllowed(system))
     return;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(system, [&system] {
-      system,
-      [&system] {
     if (s_undo_load_buffer.empty())
     {
       PanicAlertFmtT("There is nothing to undo!");
@@ -994,8 +981,7 @@ void UndoLoadState(Core::System& system)
     {
       LoadFromBuffer(system, s_undo_load_buffer);
     }
-      },
+  });
-      false);
 }
 
 // Load the state that the last save state overwritten on

Source/Core/DolphinQt/GBAWidget.cpp

@@ -37,9 +37,7 @@
 
 static void RestartCore(const std::weak_ptr<HW::GBA::Core>& core, std::string_view rom_path = {})
 {
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(Core::System::GetInstance(), [core, rom_path = std::string(rom_path)] {
-      Core::System::GetInstance(),
-      [core, rom_path = std::string(rom_path)] {
     if (auto core_ptr = core.lock())
     {
       auto& info = Config::MAIN_GBA_ROM_PATHS[core_ptr->GetCoreInfo().device_number];
@@ -52,19 +50,15 @@ static void RestartCore(const std::weak_ptr<HW::GBA::Core>& core, std::string_vi
       Config::SetCurrent(info, Config::GetBase(info));
       core_ptr->Start(core_timing.GetTicks());
     }
-      },
+  });
-      false);
 }
 
 static void QueueEReaderCard(const std::weak_ptr<HW::GBA::Core>& core, std::string_view card_path)
 {
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(Core::System::GetInstance(), [core, card_path = std::string(card_path)] {
-      Core::System::GetInstance(),
-      [core, card_path = std::string(card_path)] {
     if (auto core_ptr = core.lock())
       core_ptr->EReaderQueueCard(card_path);
-      },
+  });
-      false);
 }
 
 GBAWidget::GBAWidget(std::weak_ptr<HW::GBA::Core> core, const HW::GBA::CoreInfo& info,
@@ -161,13 +155,11 @@ void GBAWidget::ToggleDisconnect()
 
   m_force_disconnect = !m_force_disconnect;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(Core::System::GetInstance(),
-      Core::System::GetInstance(),
                        [core = m_core, force_disconnect = m_force_disconnect] {
                          if (auto core_ptr = core.lock())
                            core_ptr->SetForceDisconnect(force_disconnect);
-      },
+                       });
-      false);
 }
 
 void GBAWidget::LoadROM()
@@ -224,8 +216,7 @@ void GBAWidget::DoState(bool export_state)
   if (state_path.isEmpty())
     return;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(Core::System::GetInstance(),
-      Core::System::GetInstance(),
                        [export_state, core = m_core, state_path = state_path.toStdString()] {
                          if (auto core_ptr = core.lock())
                          {
@@ -234,8 +225,7 @@ void GBAWidget::DoState(bool export_state)
                            else
                              core_ptr->ImportState(state_path);
                          }
-      },
+                       });
-      false);
 }
 
 void GBAWidget::ImportExportSave(bool export_save)
@@ -255,8 +245,7 @@ void GBAWidget::ImportExportSave(bool export_save)
   if (save_path.isEmpty())
     return;
 
-  Core::RunOnCPUThread(
+  Core::RunOnCPUThread(Core::System::GetInstance(),
-      Core::System::GetInstance(),
                        [export_save, core = m_core, save_path = save_path.toStdString()] {
                          if (auto core_ptr = core.lock())
                          {
@@ -265,8 +254,7 @@ void GBAWidget::ImportExportSave(bool export_save)
                            else
                              core_ptr->ImportSave(save_path);
                          }
-      },
+                       });
-      false);
 }
 
 void GBAWidget::Resize(int scale)