From ad49c54531d308f04f69e37ee7b3ba3f71991768 Mon Sep 17 00:00:00 2001
From: Eladash <elad3356p@gmail.com>
Date: Thu, 18 Mar 2021 11:09:42 +0200
Subject: [PATCH] Fix race in render_creator (#9939)

---
 rpcs3/rpcs3qt/render_creator.cpp | 37 ++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/rpcs3/rpcs3qt/render_creator.cpp b/rpcs3/rpcs3qt/render_creator.cpp
index e30f7016df..d03e94a929 100644
--- a/rpcs3/rpcs3qt/render_creator.cpp
+++ b/rpcs3/rpcs3qt/render_creator.cpp
@@ -31,43 +31,49 @@ render_creator::render_creator(QObject *parent) : QObject(parent)
 
 	static std::mutex mtx;
 	static std::condition_variable cond;
-	static bool thread_running = true;
-	static bool device_found = false;
+	static bool work_done = false;
 
-	static QStringList compatible_gpus;
-
-	auto enum_thread_v = new named_thread("Vulkan Device Enumeration Thread"sv, [&]()
+	auto enum_thread_v = new named_thread("Vulkan Device Enumeration Thread"sv, [&, adapters = &this->vulkan_adapters]()
 	{
 		thread_ctrl::scoped_priority low_prio(-1);
 
 		vk::instance device_enum_context;
+
+		std::unique_lock lock(mtx, std::defer_lock);
+
 		if (device_enum_context.create("RPCS3", true))
 		{
 			device_enum_context.bind();
 			std::vector<vk::physical_device>& gpus = device_enum_context.enumerate_devices();
 
-			if (!gpus.empty())
-			{
-				device_found = true;
+			lock.lock();
 
+			if (!work_done) // The spawning thread gave up, do not attempt to modify vulkan_adapters
+			{
 				for (auto& gpu : gpus)
 				{
-					compatible_gpus.append(qstr(gpu.get_name()));
+					adapters->append(qstr(gpu.get_name()));
 				}
 			}
 		}
+		else
+		{
+			lock.lock();
+		}
 
-		std::scoped_lock{ mtx }, thread_running = false;
+		work_done = true;
+		lock.unlock();
 		cond.notify_all();
 	});
 
 	std::unique_ptr<std::remove_pointer_t<decltype(enum_thread_v)>> enum_thread(enum_thread_v);
+
+	if ([&]()
 	{
 		std::unique_lock lck(mtx);
-		cond.wait_for(lck, std::chrono::seconds(10), [&] { return !thread_running; });
-	}
-
-	if (thread_running)
+		cond.wait_for(lck, std::chrono::seconds(10), [&] { return work_done; });
+		return !std::exchange(work_done, true); // If thread hasn't done its job yet, it won't anymore
+	}())
 	{
 		enum_thread.release(); // Detach thread (destructor is not called)
 
@@ -88,8 +94,7 @@ render_creator::render_creator(QObject *parent) : QObject(parent)
 	}
 	else
 	{
-		supports_vulkan = device_found;
-		vulkan_adapters = std::move(compatible_gpus);
+		supports_vulkan = !vulkan_adapters.isEmpty();
 		enum_thread.reset(); // Join thread
 	}
 #endif