From 44c7440702249a02adb681fb738967bb28bfcc5f Mon Sep 17 00:00:00 2001
From: Jordan Woyak <jordan.woyak@gmail.com>
Date: Sun, 23 Nov 2025 18:46:29 -0600
Subject: [PATCH] Common:: Add DummyMutex and make WorkQueueThreadBase use it.

---
 Source/Core/Common/Mutex.h           | 14 ++++++++++++++
 Source/Core/Common/WorkQueueThread.h | 16 ++--------------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/Source/Core/Common/Mutex.h b/Source/Core/Common/Mutex.h
index 22aebd08b1b..fbb7c1a4c7f 100644
--- a/Source/Core/Common/Mutex.h
+++ b/Source/Core/Common/Mutex.h
@@ -48,4 +48,18 @@ using AtomicMutex = detail::AtomicMutexBase<true>;
 // Very fast to lock and unlock when uncontested (~3x faster than std::mutex).
 using SpinMutex = detail::AtomicMutexBase<false>;
 
+// This "mutex" class provides no actual thread synchronization.
+// It has a std::shared_mutex interface only to be compatible with standard locks.
+// Useful when template parameters can determine that a mutex is not actually needed.
+struct DummyMutex
+{
+  constexpr void lock() {}
+  constexpr bool try_lock() { return true; }
+  constexpr void unlock() {}
+
+  constexpr void lock_shared() {}
+  constexpr bool try_lock_shared() { return true; }
+  constexpr void unlock_shared() {}
+};
+
 }  // namespace Common
diff --git a/Source/Core/Common/WorkQueueThread.h b/Source/Core/Common/WorkQueueThread.h
index 8816ddda16d..6a5eaa73b25 100644
--- a/Source/Core/Common/WorkQueueThread.h
+++ b/Source/Core/Common/WorkQueueThread.h
@@ -10,6 +10,7 @@
 #include <thread>
 
 #include "Common/Event.h"
+#include "Common/Mutex.h"
 #include "Common/SPSCQueue.h"
 #include "Common/Thread.h"
 
@@ -128,19 +129,7 @@ private:
     m_commands.Clear();
   }
 
-  auto GetLockGuard()
-  {
-    struct DummyLockGuard
-    {
-      // Silences unused variable warning.
-      ~DummyLockGuard() { void(); }
-    };
-
-    if constexpr (IsSingleProducer)
-      return DummyLockGuard{};
-    else
-      return std::lock_guard{m_mutex};
-  }
+  auto GetLockGuard() { return std::lock_guard{m_mutex}; }
 
   bool IsRunning() { return m_thread.joinable(); }
 
@@ -177,7 +166,6 @@ private:
   Common::WaitableSPSCQueue<CommandFunction> m_commands;
   Common::Event m_event;
 
-  using DummyMutex = std::type_identity<void>;
   using ProducerMutex = std::conditional_t<IsSingleProducer, DummyMutex, std::recursive_mutex>;
   ProducerMutex m_mutex;
 };