From 06afa0036a27bdad5700ce44776d795e7d43ee6b Mon Sep 17 00:00:00 2001
From: Jordan Woyak <jordan.woyak@gmail.com>
Date: Fri, 4 Apr 2025 19:13:53 -0500
Subject: [PATCH] CoreTiming: Fix Precision Frame Timing in Dual Core mode on
 Windows.

---
 Source/Core/Core/CoreTiming.cpp | 24 +++++++++++++++---------
 Source/Core/Core/CoreTiming.h   |  7 ++++---
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/Source/Core/Core/CoreTiming.cpp b/Source/Core/Core/CoreTiming.cpp
index b0aca0168a..067587ede6 100644
--- a/Source/Core/Core/CoreTiming.cpp
+++ b/Source/Core/Core/CoreTiming.cpp
@@ -373,22 +373,28 @@ TimePoint CoreTimingManager::GetTargetHostTime(s64 target_cycle)
 
 void CoreTimingManager::SleepUntil(TimePoint time_point)
 {
-  const TimePoint time = Clock::now();
-
-  if (time >= time_point)
-    return;
-
-  if (m_use_precision_timer)
-    m_precision_timer.SleepUntil(time_point);
-  else
-    std::this_thread::sleep_until(time_point);
+  const bool use_precision_timer = m_use_precision_timer.load(std::memory_order_relaxed);
 
   if (Core::IsCPUThread())
   {
+    const TimePoint time = Clock::now();
+
+    if (use_precision_timer)
+      m_precision_cpu_timer.SleepUntil(time_point);
+    else
+      std::this_thread::sleep_until(time_point);
+
     // Count amount of time sleeping for analytics
     const TimePoint time_after_sleep = Clock::now();
     g_perf_metrics.CountThrottleSleep(time_after_sleep - time);
   }
+  else
+  {
+    if (use_precision_timer)
+      m_precision_gpu_timer.SleepUntil(time_point);
+    else
+      std::this_thread::sleep_until(time_point);
+  }
 }
 
 void CoreTimingManager::Throttle(const s64 target_cycle)
diff --git a/Source/Core/Core/CoreTiming.h b/Source/Core/Core/CoreTiming.h
index 8200da3ded..f0ed02ea64 100644
--- a/Source/Core/Core/CoreTiming.h
+++ b/Source/Core/Core/CoreTiming.h
@@ -159,7 +159,7 @@ public:
   // Throttle the CPU to the specified target cycle.
   void Throttle(const s64 target_cycle);
 
-  // May be used from any thread.
+  // May be used from CPU or GPU thread.
   void SleepUntil(TimePoint time_point);
 
   // Used by VideoInterface
@@ -216,8 +216,9 @@ private:
   int DowncountToCycles(int downcount) const;
   int CyclesToDowncount(int cycles) const;
 
-  bool m_use_precision_timer = false;
-  Common::PrecisionTimer m_precision_timer;
+  std::atomic_bool m_use_precision_timer = false;
+  Common::PrecisionTimer m_precision_cpu_timer;
+  Common::PrecisionTimer m_precision_gpu_timer;
 };
 
 }  // namespace CoreTiming