From 3455a0d15184076a2d010e88f0870523d79fd345 Mon Sep 17 00:00:00 2001
From: Stenzek <stenzek@gmail.com>
Date: Tue, 20 Aug 2024 11:50:52 +1000
Subject: [PATCH] System: Fix lockup with runahead enabled

---
 src/core/cpu_core.cpp     |  2 +-
 src/core/cpu_core.h       |  2 +-
 src/core/system.cpp       | 33 ++++++++++++++-------------------
 src/core/timing_event.cpp | 12 ++++++++++--
 4 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/src/core/cpu_core.cpp b/src/core/cpu_core.cpp
index ffc2ea3fa..5335cff52 100644
--- a/src/core/cpu_core.cpp
+++ b/src/core/cpu_core.cpp
@@ -2016,7 +2016,7 @@ bool CPU::UpdateDebugDispatcherFlag()
   return true;
 }
 
-void CPU::ExitExecution()
+[[noreturn]] void CPU::ExitExecution()
 {
   // can't exit while running events without messing things up
   DebugAssert(!TimingEvents::IsRunningEvents());
diff --git a/src/core/cpu_core.h b/src/core/cpu_core.h
index 019f04205..e65e22566 100644
--- a/src/core/cpu_core.h
+++ b/src/core/cpu_core.h
@@ -145,7 +145,7 @@ void ExecutionModeChanged();
 void Execute();
 
 // Forces an early exit from the CPU dispatcher.
-void ExitExecution();
+[[noreturn]] void ExitExecution();
 
 ALWAYS_INLINE static Registers& GetRegs()
 {
diff --git a/src/core/system.cpp b/src/core/system.cpp
index 217103181..7adbcd2c1 100644
--- a/src/core/system.cpp
+++ b/src/core/system.cpp
@@ -204,7 +204,7 @@ static u32 CompressAndWriteStateData(std::FILE* fp, std::span<const u8> src, Sav
 static bool DoState(StateWrapper& sw, GPUTexture** host_texture, bool update_display, bool is_memory_state);
 
 static bool IsExecutionInterrupted();
-static void ExitExecution();
+static void CheckForAndExitExecution();
 
 static void SetRewinding(bool enabled);
 static bool SaveRewindState();
@@ -557,15 +557,20 @@ bool System::IsRunning()
   return s_state == State::Running;
 }
 
-bool System::IsExecutionInterrupted()
+ALWAYS_INLINE bool System::IsExecutionInterrupted()
 {
   return s_state != State::Running || s_system_interrupted;
 }
 
-void System::ExitExecution()
+ALWAYS_INLINE_RELEASE void System::CheckForAndExitExecution()
 {
-  TimingEvents::CancelRunningEvent();
-  CPU::ExitExecution();
+  if (IsExecutionInterrupted()) [[unlikely]]
+  {
+    s_system_interrupted = false;
+
+    TimingEvents::CancelRunningEvent();
+    CPU::ExitExecution();
+  }
 }
 
 bool System::IsPaused()
@@ -2048,13 +2053,7 @@ void System::FrameDone()
       Host::PumpMessagesOnCPUThread();
       InputManager::PollSources();
       g_gpu->RestoreDeviceContext();
-
-      if (IsExecutionInterrupted())
-      {
-        s_system_interrupted = false;
-        ExitExecution();
-        return;
-      }
+      CheckForAndExitExecution();
     }
 
     if (DoRunahead())
@@ -2159,13 +2158,7 @@ void System::FrameDone()
   {
     Host::PumpMessagesOnCPUThread();
     InputManager::PollSources();
-
-    if (IsExecutionInterrupted())
-    {
-      s_system_interrupted = false;
-      ExitExecution();
-      return;
-    }
+    CheckForAndExitExecution();
   }
 
   g_gpu->RestoreDeviceContext();
@@ -4831,6 +4824,8 @@ bool System::DoRunahead()
 
     // we don't want to save the frame we just loaded. but we are "one frame ahead", because the frame we just tossed
     // was never saved, so return but don't decrement the counter
+    InterruptExecution();
+    CheckForAndExitExecution();
     return true;
   }
   else if (s_runahead_replay_frames == 0)
diff --git a/src/core/timing_event.cpp b/src/core/timing_event.cpp
index c9cd621d6..caf980f1a 100644
--- a/src/core/timing_event.cpp
+++ b/src/core/timing_event.cpp
@@ -384,7 +384,7 @@ void TimingEvents::CommitLeftoverTicks()
 {
 #ifdef _DEBUG
   if (s_state.event_run_tick_counter > s_state.global_tick_counter)
-    WARNING_LOG("Late-running {} ticks before execution", s_state.event_run_tick_counter - s_state.global_tick_counter);
+    DEV_LOG("Late-running {} ticks before execution", s_state.event_run_tick_counter - s_state.global_tick_counter);
 #endif
 
   CommitGlobalTicks(s_state.event_run_tick_counter);
@@ -441,6 +441,7 @@ bool TimingEvents::DoState(StateWrapper& sw)
     }
 
     DEBUG_LOG("Loaded {} events from save state.", event_count);
+    s_state.current_event = nullptr;
 
     // Add pending ticks to the CPU, this'll happen if we saved state when we weren't paused.
     const TickCount pending_ticks =
@@ -489,7 +490,12 @@ bool TimingEvents::DoState(StateWrapper& sw)
       }
 
       DEBUG_LOG("Loaded {} events from save state.", event_count);
+
+      // Even if we're actually running an event, we don't want to set it to a new counter.
+      s_state.current_event = nullptr;
+
       SortEvents();
+      UpdateCPUDowncount();
     }
     else
     {
@@ -498,7 +504,9 @@ bool TimingEvents::DoState(StateWrapper& sw)
       for (TimingEvent* event = s_state.active_events_head; event; event = event->next)
       {
         sw.Do(&event->m_name);
-        sw.Do(&event->m_next_run_time);
+        GlobalTicks next_run_time =
+          (s_state.current_event == event) ? s_state.current_event_next_run_time : event->m_next_run_time;
+        sw.Do(&next_run_time);
         sw.Do(&event->m_last_run_time);
         sw.Do(&event->m_period);
         sw.Do(&event->m_interval);