frontend: bound the wait for the emulation thread at shutdown

426f120ee8 dropped the 10 s wait and terminate() fallback when stopping
emulation, and ShutdownGame and closeEvent now wait for the emulation
thread with no limit. If the thread hangs (for example a GPU or present
deadlock), stopping a game, switching games or quitting never completes.

Keep the asynchronous teardown, but once the thread has been asked to
stop, give it 10 s and then terminate it and finish cleanup, as before.
ShutdownGame's nested event loop gets the same bound. A terminated
thread is logged as an error.

Assisted-by: Claude Sonnet 5.5 (implementation and commit message)

2 files changed, 30 insertions, 4 deletions

diff --git a/src/yuzu/main_window.cpp b/src/yuzu/main_window.cpp
index e5a8f81424..02b36cf9cf 100644
--- a/src/yuzu/main_window.cpp
+++ b/src/yuzu/main_window.cpp
@@ -320,6 +320,7 @@ __declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;
 
 constexpr int default_mouse_hide_timeout = 2500;
 constexpr int default_input_update_timeout = 1;
+constexpr int EmuThreadStopTimeoutMs = 10'000;
 
 constexpr size_t CopyBufferSize = 1_MiB;
 
@@ -2209,6 +2210,23 @@ void MainWindow::OnShutdownBeginDialog() {
 void MainWindow::OnEmulationStopTimeExpired() {
     if (QtCommon::emu_thread) {
         QtCommon::emu_thread->ForceStop();
+        emu_terminate_timer.setSingleShot(true);
+        emu_terminate_timer.start(EmuThreadStopTimeoutMs);
+        connect(&emu_terminate_timer, &QTimer::timeout, this, &MainWindow::OnEmulationStopTimeout,
+                Qt::UniqueConnection);
+    }
+}
+
+void MainWindow::OnEmulationStopTimeout() {
+    TerminateEmulationThread();
+    OnEmulationStopped();
+}
+
+void MainWindow::TerminateEmulationThread() {
+    if (QtCommon::emu_thread && QtCommon::emu_thread->isRunning()) {
+        LOG_ERROR(Frontend, "Emulation thread failed to stop, terminating it");
+        QtCommon::emu_thread->terminate();
+        QtCommon::emu_thread->wait();
     }
 }
 
@@ -2220,6 +2238,7 @@ void MainWindow::OnEmulationStopped() {
         return;
     }
     shutdown_timer.stop();
+    emu_terminate_timer.stop();
     if (QtCommon::emu_thread) {
         QtCommon::emu_thread->disconnect();
         QtCommon::emu_thread->wait();
@@ -2309,13 +2328,17 @@ void MainWindow::ShutdownGame() {
     play_time_manager->Stop();
     OnShutdownBegin();
     OnEmulationStopTimeExpired();
-    if (QtCommon::emu_thread) {
+    emu_terminate_timer.stop();
+    if (QtCommon::emu_thread && QtCommon::emu_thread->isRunning()) {
         QEventLoop loop;
+        QTimer timeout;
+        timeout.setSingleShot(true);
         connect(QtCommon::emu_thread.get(), &QThread::finished, &loop, &QEventLoop::quit);
-        if (QtCommon::emu_thread->isRunning()) {
-            loop.exec(QEventLoop::ExcludeUserInputEvents);
-        }
+        connect(&timeout, &QTimer::timeout, &loop, &QEventLoop::quit);
+        timeout.start(EmuThreadStopTimeoutMs);
+        loop.exec(QEventLoop::ExcludeUserInputEvents);
     }
+    TerminateEmulationThread();
     OnEmulationStopped();
 }
 
diff --git a/src/yuzu/main_window.h b/src/yuzu/main_window.h
index e2c5a0f6db..a3b030a6a6 100644
--- a/src/yuzu/main_window.h
+++ b/src/yuzu/main_window.h
@@ -279,6 +279,7 @@ private:
                   StartGameType with_config = StartGameType::Normal);
     void BootGameFromList(const QString& filename, StartGameType with_config);
     void ShutdownGame();
+    void TerminateEmulationThread();
 
     void SetDiscordEnabled(bool state);
     void LoadAmiibo(const QString& filename);
@@ -437,6 +438,7 @@ private slots:
     void OnShutdownBeginDialog();
     void OnEmulationStopped();
     void OnEmulationStopTimeExpired();
+    void OnEmulationStopTimeout();
 
 #ifdef ENABLE_UPDATE_CHECKER
     void OnEmulatorUpdateAvailable();
@@ -506,6 +508,7 @@ private:
     GameList* game_list = nullptr;
     LoadingScreen* loading_screen = nullptr;
     QTimer shutdown_timer;
+    QTimer emu_terminate_timer;
     OverlayDialog* shutdown_dialog{};
     PerformanceOverlay* perf_overlay = nullptr;
 #ifdef HAS_RESHADE