From 54b4efff6b14a2dc0be6d6a284be8b27750ceecb Mon Sep 17 00:00:00 2001
From: mathieui <mathieui@mathieui.net>
Date: Sat, 30 Apr 2016 13:29:11 +0200
Subject: [PATCH] GCAdapter: improve thread safety
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make sure Reset() can’t be run concurrently with AddGCAdapter() or
ResetRumble() (which is called on other threads) which can cause
crashes (issue #9462)
---
 Source/Core/InputCommon/GCAdapter.cpp | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/Source/Core/InputCommon/GCAdapter.cpp b/Source/Core/InputCommon/GCAdapter.cpp
index eceed1ed0b..4728a9f49f 100644
--- a/Source/Core/InputCommon/GCAdapter.cpp
+++ b/Source/Core/InputCommon/GCAdapter.cpp
@@ -22,6 +22,7 @@ namespace GCAdapter
 {
 static bool CheckDeviceAccess(libusb_device* device);
 static void AddGCAdapter(libusb_device* device);
+static void ResetRumbleLockNeeded();
 
 static bool s_detected = false;
 static libusb_device_handle* s_handle = nullptr;
@@ -37,6 +38,7 @@ static std::atomic<int> s_controller_payload_size = {0};
 static std::thread s_adapter_thread;
 static Common::Flag s_adapter_thread_running;
 
+static std::mutex s_init_mutex;
 static std::thread s_adapter_detect_thread;
 static Common::Flag s_adapter_detect_thread_running;
 
@@ -77,7 +79,10 @@ static int HotplugCallback(libusb_context* ctx, libusb_device* dev, libusb_hotpl
 	if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED)
 	{
 		if (s_handle == nullptr && CheckDeviceAccess(dev))
+		{
+			std::lock_guard<std::mutex> lk(s_init_mutex);
 			AddGCAdapter(dev);
+		}
 	}
 	else if (event == LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT)
 	{
@@ -115,6 +120,7 @@ static void ScanThreadFunc()
 		{
 			if (s_handle == nullptr)
 			{
+				std::lock_guard<std::mutex> lk(s_init_mutex);
 				Setup();
 				if (s_detected && s_detect_callback != nullptr)
 					s_detect_callback();
@@ -306,7 +312,7 @@ static void AddGCAdapter(libusb_device* device)
 	s_detected = true;
 	if (s_detect_callback != nullptr)
 		s_detect_callback();
-	ResetRumble();
+	ResetRumbleLockNeeded();
 }
 
 void Shutdown()
@@ -329,6 +335,9 @@ void Shutdown()
 
 void Reset()
 {
+	std::unique_lock<std::mutex> lock(s_init_mutex, std::defer_lock);
+	if (!lock.try_lock())
+		return;
 	if (!s_detected)
 		return;
 
@@ -439,10 +448,20 @@ bool UseAdapter()
 
 void ResetRumble()
 {
-	if (!UseAdapter())
+	std::unique_lock<std::mutex> lock(s_init_mutex, std::defer_lock);
+	if (!lock.try_lock())
 		return;
-	if (s_handle == nullptr || !s_detected)
+	ResetRumbleLockNeeded();
+}
+
+// Needs to be called when s_init_mutex is locked in order to avoid
+// being called while the libusb state is being reset
+static void ResetRumbleLockNeeded()
+{
+	if (!UseAdapter() || (s_handle == nullptr || !s_detected))
+	{
 		return;
+	}
 
 	std::fill(std::begin(s_controller_rumble), std::end(s_controller_rumble), 0);