Core: Make PerfStats internally locked

More ergonomic to use and will be required for upcoming changes.

src/core/perf_stats.cpp

@@ -3,6 +3,7 @@
 // Refer to the license.txt file included.
 
 #include <chrono>
+#include <mutex>
 #include "core/hw/gpu.h"
 #include "core/perf_stats.h"
 
@@ -12,10 +13,14 @@ using std::chrono::duration_cast;
 namespace Core {
 
 void PerfStats::BeginSystemFrame() {
+    std::lock_guard<std::mutex> lock(object_mutex);
+
     frame_begin = Clock::now();
 }
 
 void PerfStats::EndSystemFrame() {
+    std::lock_guard<std::mutex> lock(object_mutex);
+
     auto frame_end = Clock::now();
     accumulated_frametime += frame_end - frame_begin;
     system_frames += 1;
@@ -25,10 +30,14 @@ void PerfStats::EndSystemFrame() {
 }
 
 void PerfStats::EndGameFrame() {
+    std::lock_guard<std::mutex> lock(object_mutex);
+
     game_frames += 1;
 }
 
 PerfStats::Results PerfStats::GetAndResetStats(u64 current_system_time_us) {
+    std::lock_guard<std::mutex> lock(object_mutex);
+
     auto now = Clock::now();
     // Walltime elapsed since stats were reset
     auto interval = duration_cast<DoubleSecs>(now - reset_point).count();
@@ -54,6 +63,8 @@ PerfStats::Results PerfStats::GetAndResetStats(u64 current_system_time_us) {
 }
 
 double PerfStats::GetLastFrameTimeScale() {
+    std::lock_guard<std::mutex> lock(object_mutex);
+
     constexpr double FRAME_LENGTH = 1.0 / GPU::SCREEN_REFRESH_RATE;
     return duration_cast<DoubleSecs>(previous_frame_length).count() / FRAME_LENGTH;
 }