From 56ea1c1d74f349a1ed412b7e604decf0fadc9f6c Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Sat, 5 Feb 2022 19:49:06 +0100
Subject: [PATCH 1/2] Core/State: Guard SaveAs() and LoadAs() with a mutex.

---
 Source/Core/Core/State.cpp | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/Source/Core/Core/State.cpp b/Source/Core/Core/State.cpp
index f89c1fc79e..e3f382a610 100644
--- a/Source/Core/Core/State.cpp
+++ b/Source/Core/Core/State.cpp
@@ -64,7 +64,7 @@ static AfterLoadCallbackFunc s_on_after_load_callback;
 // Temporary undo state buffer
 static std::vector<u8> g_undo_load_buffer;
 static std::vector<u8> g_current_buffer;
-static bool s_load_or_save_in_progress;
+static std::mutex s_load_or_save_in_progress_mutex;
 
 static std::mutex g_cs_undo_load_buffer;
 static std::mutex g_cs_current_buffer;
@@ -403,11 +403,10 @@ static void CompressAndDumpState(CompressAndDumpState_args save_args)
 
 void SaveAs(const std::string& filename, bool wait)
 {
-  if (s_load_or_save_in_progress)
+  std::unique_lock lk(s_load_or_save_in_progress_mutex, std::try_to_lock);
+  if (!lk)
     return;
 
-  s_load_or_save_in_progress = true;
-
   Core::RunOnCPUThread(
       [&] {
         // Measure the size of the buffer.
@@ -446,8 +445,6 @@ void SaveAs(const std::string& filename, bool wait)
         }
       },
       true);
-
-  s_load_or_save_in_progress = false;
 }
 
 bool ReadHeader(const std::string& filename, StateHeader& header)
@@ -550,17 +547,18 @@ static void LoadFileStateData(const std::string& filename, std::vector<u8>& ret_
 
 void LoadAs(const std::string& filename)
 {
-  if (!Core::IsRunning() || s_load_or_save_in_progress)
-  {
+  if (!Core::IsRunning())
     return;
-  }
-  else if (NetPlay::IsNetPlayRunning())
+
+  if (NetPlay::IsNetPlayRunning())
   {
     OSD::AddMessage("Loading savestates is disabled in Netplay to prevent desyncs");
     return;
   }
 
-  s_load_or_save_in_progress = true;
+  std::unique_lock lk(s_load_or_save_in_progress_mutex, std::try_to_lock);
+  if (!lk)
+    return;
 
   Core::RunOnCPUThread(
       [&] {
@@ -617,8 +615,6 @@ void LoadAs(const std::string& filename)
           s_on_after_load_callback();
       },
       true);
-
-  s_load_or_save_in_progress = false;
 }
 
 void SetOnAfterLoadCallback(AfterLoadCallbackFunc callback)

From 73311694b04cc3830689726ddda879e0a0d8b069 Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Sat, 5 Feb 2022 19:56:44 +0100
Subject: [PATCH 2/2] Core/State: Guard g_save_thread with a mutex.

---
 Source/Core/Core/State.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Source/Core/Core/State.cpp b/Source/Core/Core/State.cpp
index e3f382a610..b1a3c70910 100644
--- a/Source/Core/Core/State.cpp
+++ b/Source/Core/Core/State.cpp
@@ -70,6 +70,7 @@ static std::mutex g_cs_undo_load_buffer;
 static std::mutex g_cs_current_buffer;
 static Common::Event g_compressAndDumpStateSyncEvent;
 
+static std::recursive_mutex g_save_thread_mutex;
 static std::thread g_save_thread;
 
 // Don't forget to increase this after doing changes on the savestate system
@@ -434,8 +435,12 @@ void SaveAs(const std::string& filename, bool wait)
           save_args.filename = filename;
           save_args.wait = wait;
 
-          Flush();
-          g_save_thread = std::thread(CompressAndDumpState, save_args);
+          {
+            std::lock_guard lk(g_save_thread_mutex);
+            Flush();
+            g_save_thread = std::thread(CompressAndDumpState, save_args);
+          }
+
           g_compressAndDumpStateSyncEvent.Wait();
         }
         else
@@ -695,6 +700,8 @@ void SaveFirstSaved()
 
 void Flush()
 {
+  std::lock_guard lk(g_save_thread_mutex);
+
   // If already saving state, wait for it to finish
   if (g_save_thread.joinable())
     g_save_thread.join();