DVDInterface: Simplify calling ChangeDisc from CPU thread

Source/Core/Core/HW/DVDInterface.cpp

@@ -472,10 +472,20 @@ static void InsertDiscCallback(u64 userdata, s64 cyclesLate)
   delete _FileName;
 }
 
-void ChangeDisc(const std::string& newFileName)
+// Can only be called by the host thread
+void ChangeDiscAsHost(const std::string& newFileName)
 {
-  // WARNING: Can only run on Host Thread
   bool was_unpaused = Core::PauseAndLock(true);
+
+  // The host thread is now temporarily the CPU thread
+  ChangeDiscAsCPU(newFileName);
+
+  Core::PauseAndLock(false, was_unpaused);
+}
+
+// Can only be called by the CPU thread
+void ChangeDiscAsCPU(const std::string& newFileName)
+{
   std::string* _FileName = new std::string(newFileName);
   CoreTiming::ScheduleEvent(0, s_eject_disc);
   CoreTiming::ScheduleEvent(500000000, s_insert_disc, (u64)_FileName);
@@ -492,7 +502,6 @@ void ChangeDisc(const std::string& newFileName)
     }
     Movie::g_discChange = fileName.substr(sizeofpath);
   }
-  Core::PauseAndLock(false, was_unpaused);
 }
 
 void SetLidOpen(bool open)

Source/Core/Core/HW/DVDInterface.h

@@ -108,7 +108,8 @@ bool VolumeIsValid();
 // Disc detection and swapping
 void SetDiscInside(bool _DiscInside);
 bool IsDiscInside();
-void ChangeDisc(const std::string& fileName);  // [NOT THREADSAFE] Host only
+void ChangeDiscAsHost(const std::string& path);  // Can only be called by the host thread
+void ChangeDiscAsCPU(const std::string& path);   // Can only be called by the CPU thread
 
 // DVD Access Functions
 bool ChangePartition(u64 offset);

Source/Core/Core/Movie.cpp

@@ -1211,36 +1211,27 @@ void PlayController(GCPadStatus* PadStatus, int controllerID)
     PadStatus->button |= PAD_TRIGGER_R;
   if (s_padState.disc)
   {
-    // This implementation assumes the disc change will only happen once. Trying to change more than
-    // that will cause
-    // it to load the last disc every time. As far as i know though, there are no 3+ disc games, so
-    // this should be fine.
-    CPU::Break();
+    // This implementation assumes the disc change will only happen once. Trying
+    // to change more than that will cause it to load the last disc every time.
+    // As far as I know, there are no 3+ disc games, so this should be fine.
     bool found = false;
     std::string path;
-    for (size_t i = 0; i < SConfig::GetInstance().m_ISOFolder.size(); ++i)
+    for (const std::string& iso_folder : SConfig::GetInstance().m_ISOFolder)
     {
-      path = SConfig::GetInstance().m_ISOFolder[i];
-      if (File::Exists(path + '/' + g_discChange))
+      path = iso_folder + '/' + g_discChange;
+      if (File::Exists(path))
       {
         found = true;
         break;
       }
     }
     if (found)
     {
-      path += '/' + g_discChange;
-
-      Core::QueueHostJob([=] {
-        if (!Movie::IsPlayingInput())
-          return;
-
-        DVDInterface::ChangeDisc(path);
-        CPU::EnableStepping(false);
-      });
+      DVDInterface::ChangeDiscAsCPU(path);
     }
     else
     {
+      CPU::Break();
       PanicAlertT("Change the disc to %s", g_discChange.c_str());
     }
   }

Source/Core/DolphinWX/Frame.cpp

@@ -124,7 +124,7 @@ void CRenderFrame::OnDropFiles(wxDropFilesEvent& event)
   }
   else
   {
-    DVDInterface::ChangeDisc(filepath);
+    DVDInterface::ChangeDiscAsHost(filepath);
   }
 }
 

Source/Core/DolphinWX/FrameTools.cpp

@@ -691,7 +691,7 @@ void CFrame::DoOpen(bool Boot)
   }
   else
   {
-    DVDInterface::ChangeDisc(WxStrToStr(path));
+    DVDInterface::ChangeDiscAsHost(WxStrToStr(path));
   }
 }
 

Source/Core/DolphinWX/GameListCtrl.cpp

@@ -1331,7 +1331,7 @@ void CGameListCtrl::OnChangeDisc(wxCommandEvent& WXUNUSED(event))
   const GameListItem* iso = GetSelectedISO();
   if (!iso || !Core::IsRunning())
     return;
-  DVDInterface::ChangeDisc(WxStrToStr(iso->GetFileName()));
+  DVDInterface::ChangeDiscAsHost(WxStrToStr(iso->GetFileName()));
 }
 
 void CGameListCtrl::OnSize(wxSizeEvent& event)