Lock the video render mode against concurrent readers

VIConfigure writes the mode on the game side while the GX thread, the
frame worker and the window code read its size. The resize request is
made after the lock is released.

From upstream patchzyy/Wiicompiled 6f14bde (#244).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wg7mB8ogCWmp9GH19Uc82B

aurora-main/lib/dolphin/vi/vi.cpp

@@ -7,11 +7,13 @@
 #include <algorithm>
 #include <atomic>
 #include <optional>
+#include <mutex>
 
 namespace aurora::vi {
 std::optional<GXRenderModeObj> g_renderMode;
 namespace {
 std::atomic<float> g_presentAspectCorrection{1.f};
+std::mutex g_renderModeMutex;
 
 float calculate_present_aspect_correction(const GXRenderModeObj& rm) noexcept {
   if (rm.viWidth == 0 || rm.viHeight == 0) {
@@ -29,9 +31,8 @@ float calculate_present_aspect_correction(const GXRenderModeObj& rm) noexcept {
   const float verticalFill = static_cast<float>(rm.viHeight) / nominalActiveHeight;
   return horizontalFill / verticalFill;
 }
-} // namespace
 
-Vec2<uint32_t> render_mode_size() noexcept {
+Vec2<uint32_t> render_mode_size_locked() noexcept {
   if (!g_renderMode) {
     return {640, 528};
   }
@@ -40,18 +41,31 @@ Vec2<uint32_t> render_mode_size() noexcept {
   return {std::max<uint32_t>(g_renderMode->fbWidth, 640), std::max<uint32_t>(g_renderMode->efbHeight, 528)};
 }
 
+} // namespace
+
+Vec2<uint32_t> render_mode_size() noexcept {
+  std::lock_guard lock(g_renderModeMutex);
+  return render_mode_size_locked();
+}
+
 void configure(const GXRenderModeObj* rm) noexcept {
-  const auto oldSize = render_mode_size();
-  if (rm == nullptr) {
-    g_renderMode.reset();
-  } else {
-    g_renderMode = *rm;
-    g_presentAspectCorrection.store(calculate_present_aspect_correction(*rm), std::memory_order_release);
+  bool sizeChanged = false;
+  {
+    std::lock_guard lock(g_renderModeMutex);
+    const auto oldSize = render_mode_size_locked();
+    if (rm == nullptr) {
+      g_renderMode.reset();
+    } else {
+      g_renderMode = *rm;
+      g_presentAspectCorrection.store(calculate_present_aspect_correction(*rm), std::memory_order_release);
+    }
+    if (rm == nullptr) {
+      g_presentAspectCorrection.store(1.f, std::memory_order_release);
+    }
+    sizeChanged = render_mode_size_locked() != oldSize;
   }
-  if (rm == nullptr) {
-    g_presentAspectCorrection.store(1.f, std::memory_order_release);
-  }
-  if (render_mode_size() != oldSize) {
+  // Never hold the mode lock across a resize request or a renderer callback.
+  if (sizeChanged) {
     window::request_frame_buffer_resize();
   }
 }
@@ -61,6 +75,7 @@ Vec2<uint32_t> configured_fb_size() noexcept {
 }
 
 Vec2<uint32_t> visible_fb_size() noexcept {
+  std::lock_guard lock(g_renderModeMutex);
   if (!g_renderMode) {
     return {640, 528};
   }