From dcf8ab01898eb71bcf4aca1fa527e6cd196367da Mon Sep 17 00:00:00 2001
From: JosJuice <josjuice@gmail.com>
Date: Wed, 21 Aug 2024 20:36:46 +0200
Subject: [PATCH] Android: Wait for surface in Run

When we boot the core, it needs to have a valid surface to draw graphics
to. Our Kotlin code does wait for a valid surface to exist before it
calls NativeLibrary.Run, but there's a chance for the surface to be
deleted before Run locks s_surface_lock. If that happens, the core boots
without a valid surface, which presumably would cause a crash. (I
haven't been able to reproduce the problem myself.)
---
 Source/Android/jni/MainAndroid.cpp | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/Source/Android/jni/MainAndroid.cpp b/Source/Android/jni/MainAndroid.cpp
index 811b28c32b..d73cd904dc 100644
--- a/Source/Android/jni/MainAndroid.cpp
+++ b/Source/Android/jni/MainAndroid.cpp
@@ -1,13 +1,9 @@
 // Copyright 2003 Dolphin Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include <EGL/egl.h>
-#include <android/log.h>
-#include <android/native_window_jni.h>
+#include <condition_variable>
 #include <cstdio>
 #include <cstdlib>
-#include <fmt/format.h>
-#include <jni.h>
 #include <memory>
 #include <mutex>
 #include <optional>
@@ -15,6 +11,12 @@
 #include <thread>
 #include <utility>
 
+#include <EGL/egl.h>
+#include <android/log.h>
+#include <android/native_window_jni.h>
+#include <fmt/format.h>
+#include <jni.h>
+
 #include "Common/AndroidAnalytics.h"
 #include "Common/Assert.h"
 #include "Common/CPUDetect.h"
@@ -77,6 +79,8 @@ Common::Event s_update_main_frame_event;
 // This exists to prevent surfaces from being destroyed during the boot process,
 // as that can lead to the boot process dereferencing nullptr.
 std::mutex s_surface_lock;
+std::condition_variable s_surface_cv;
+
 bool s_need_nonblocking_alert_msg;
 
 Common::Flag s_is_booting;
@@ -454,6 +458,8 @@ JNIEXPORT void JNICALL Java_org_dolphinemu_dolphinemu_NativeLibrary_SurfaceChang
 
   if (g_presenter)
     g_presenter->ChangeSurface(s_surf);
+
+  s_surface_cv.notify_all();
 }
 
 JNIEXPORT void JNICALL Java_org_dolphinemu_dolphinemu_NativeLibrary_SurfaceDestroyed(JNIEnv*,
@@ -487,6 +493,8 @@ JNIEXPORT void JNICALL Java_org_dolphinemu_dolphinemu_NativeLibrary_SurfaceDestr
     ANativeWindow_release(s_surf);
     s_surf = nullptr;
   }
+
+  s_surface_cv.notify_all();
 }
 
 JNIEXPORT jboolean JNICALL Java_org_dolphinemu_dolphinemu_NativeLibrary_HasSurface(JNIEnv*, jclass)
@@ -578,12 +586,14 @@ static void Run(JNIEnv* env, std::unique_ptr<BootParameters>&& boot, bool riivol
                                           volume.GetDiscNumber()));
   }
 
-  WindowSystemInfo wsi(WindowSystemType::Android, nullptr, s_surf, s_surf);
-  wsi.render_surface_scale = GetRenderSurfaceScale(env);
-
   s_need_nonblocking_alert_msg = true;
   std::unique_lock<std::mutex> surface_guard(s_surface_lock);
 
+  s_surface_cv.wait(surface_guard, []() { return s_surf != nullptr; });
+
+  WindowSystemInfo wsi(WindowSystemType::Android, nullptr, s_surf, s_surf);
+  wsi.render_surface_scale = GetRenderSurfaceScale(env);
+
   if (BootManager::BootCore(Core::System::GetInstance(), std::move(boot), wsi))
   {
     static constexpr int WAIT_STEP = 25;