From 18dcb0934217628711c5b1d22fd6d7635e683e3f Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow <fsahmkow27@gmail.com>
Date: Tue, 25 Feb 2020 12:28:55 -0400
Subject: [PATCH] HostTiming: Pause the hardware clock on pause.

---
 src/common/wall_clock.cpp       | 4 ++++
 src/common/wall_clock.h         | 2 ++
 src/common/x64/native_clock.cpp | 7 +++++++
 src/common/x64/native_clock.h   | 2 ++
 src/core/core.cpp               | 2 +-
 src/core/core_timing.cpp        | 6 ++++++
 src/core/core_timing.h          | 1 +
 7 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/common/wall_clock.cpp b/src/common/wall_clock.cpp
index d4d35f4e7..a46db6bbf 100644
--- a/src/common/wall_clock.cpp
+++ b/src/common/wall_clock.cpp
@@ -53,6 +53,10 @@ public:
         return Common::Divide128On32(temporary, 1000000000).first;
     }
 
+    void Pause(bool is_paused) override {
+        // Do nothing in this clock type.
+    }
+
 private:
     base_time_point start_time;
 };
diff --git a/src/common/wall_clock.h b/src/common/wall_clock.h
index ed284cf50..367d72134 100644
--- a/src/common/wall_clock.h
+++ b/src/common/wall_clock.h
@@ -28,6 +28,8 @@ public:
     /// Returns current wall time in emulated cpu cycles
     virtual u64 GetCPUCycles() = 0;
 
+    virtual void Pause(bool is_paused) = 0;
+
     /// Tells if the wall clock, uses the host CPU's hardware clock
     bool IsNative() const {
         return is_native;
diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index 26d4d0ba6..926f92ff8 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -65,6 +65,13 @@ u64 NativeClock::GetRTSC() {
     return accumulated_ticks;
 }
 
+void NativeClock::Pause(bool is_paused) {
+    if (!is_paused) {
+        _mm_mfence();
+        last_measure = __rdtsc();
+    }
+}
+
 std::chrono::nanoseconds NativeClock::GetTimeNS() {
     const u64 rtsc_value = GetRTSC();
     return std::chrono::nanoseconds{MultiplyAndDivide64(rtsc_value, 1000000000, rtsc_frequency)};
diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index b58cf9f5a..3851f8fc2 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -26,6 +26,8 @@ public:
 
     u64 GetCPUCycles() override;
 
+    void Pause(bool is_paused) override;
+
 private:
     u64 GetRTSC();
 
diff --git a/src/core/core.cpp b/src/core/core.cpp
index e8936b09d..1d6179a80 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -137,8 +137,8 @@ struct System::Impl {
     ResultStatus Pause() {
         status = ResultStatus::Success;
 
-        kernel.Suspend(true);
         core_timing.SyncPause(true);
+        kernel.Suspend(true);
         cpu_manager.Pause(true);
 
         return status;
diff --git a/src/core/core_timing.cpp b/src/core/core_timing.cpp
index cc32a853b..5a7abcfca 100644
--- a/src/core/core_timing.cpp
+++ b/src/core/core_timing.cpp
@@ -77,6 +77,9 @@ void CoreTiming::SyncPause(bool is_paused) {
         return;
     }
     Pause(is_paused);
+    if (!is_paused) {
+        pause_event.Set();
+    }
     event.Set();
     while (paused_set != is_paused)
         ;
@@ -197,6 +200,9 @@ void CoreTiming::ThreadLoop() {
             wait_set = false;
         }
         paused_set = true;
+        clock->Pause(true);
+        pause_event.Wait();
+        clock->Pause(false);
     }
 }
 
diff --git a/src/core/core_timing.h b/src/core/core_timing.h
index 707c8ef0c..c70b605c8 100644
--- a/src/core/core_timing.h
+++ b/src/core/core_timing.h
@@ -136,6 +136,7 @@ private:
 
     std::shared_ptr<EventType> ev_lost;
     Common::Event event{};
+    Common::Event pause_event{};
     Common::SpinLock basic_lock{};
     Common::SpinLock advance_lock{};
     std::unique_ptr<std::thread> timer_thread;