From 4ccd3e09b846725e6dd6823c4f161e770a06115e Mon Sep 17 00:00:00 2001
From: Jordan Brown <Cyberboss@users.noreply.github.com>
Date: Thu, 29 Jun 2017 14:35:47 -0400
Subject: [PATCH] DreamDaemon is now suspended while symswap happens (#54)

* DreamDaemon is now suspended while symswap happens

* Fix
---
 TGServerService/Compiler.cs            | 25 ++++++------
 TGServerService/ProcessExtension.cs    | 55 ++++++++++++++++++++++++++
 TGServerService/TGServerService.csproj |  1 +
 3 files changed, 69 insertions(+), 12 deletions(-)
 create mode 100644 TGServerService/ProcessExtension.cs

diff --git a/TGServerService/Compiler.cs b/TGServerService/Compiler.cs
index 57760fd066..63fbe5b8d8 100644
--- a/TGServerService/Compiler.cs
+++ b/TGServerService/Compiler.cs
@@ -433,20 +433,21 @@ namespace TGServerService
 							try
 							{
 								//gotta go fast
-								if (currentStatus == TGDreamDaemonStatus.Online)
+								var online = currentStatus == TGDreamDaemonStatus.Online;
+								if(online)
+									Proc.Suspend();
+								try
 								{
-									Thread.CurrentThread.Priority = ThreadPriority.Highest;
-									Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.RealTime;
-									try
-									{
-										Proc.PriorityClass = ProcessPriorityClass.Idle;
-									}
-									catch { }
+									if (Directory.Exists(GameDirLive))
+										//these two lines should be atomic but this is the best we can do
+										Directory.Delete(GameDirLive);
+									CreateSymlink(GameDirLive, resurrectee);
+								}
+								finally
+								{
+									if(online && !Proc.HasExited)
+										Proc.Resume();
 								}
-								if (Directory.Exists(GameDirLive))
-									//these two lines should be atomic but this is the best we can do
-									Directory.Delete(GameDirLive);
-								CreateSymlink(GameDirLive, resurrectee);
 							}
 							finally
 							{
diff --git a/TGServerService/ProcessExtension.cs b/TGServerService/ProcessExtension.cs
new file mode 100644
index 0000000000..3fc590b89b
--- /dev/null
+++ b/TGServerService/ProcessExtension.cs
@@ -0,0 +1,55 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace TGServerService
+{
+	//lightly massaged code from https://stackoverflow.com/a/13109774
+	public static class ProcessExtension
+	{
+		enum ThreadAccess : int
+		{
+			TERMINATE = (0x0001),
+			SUSPEND_RESUME = (0x0002),
+			GET_CONTEXT = (0x0008),
+			SET_CONTEXT = (0x0010),
+			SET_INFORMATION = (0x0020),
+			QUERY_INFORMATION = (0x0040),
+			SET_THREAD_TOKEN = (0x0080),
+			IMPERSONATE = (0x0100),
+			DIRECT_IMPERSONATION = (0x0200)
+		}
+
+		[DllImport("kernel32.dll")]
+		static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);
+		[DllImport("kernel32.dll")]
+		static extern bool CloseHandle(IntPtr hObject);
+		[DllImport("kernel32.dll")]
+		static extern uint SuspendThread(IntPtr hThread);
+		[DllImport("kernel32.dll")]
+		static extern int ResumeThread(IntPtr hThread);
+
+		public static void Suspend(this Process process)
+		{
+			foreach (ProcessThread thread in process.Threads)
+			{
+				var pOpenThread = OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint)thread.Id);
+				if (pOpenThread == IntPtr.Zero)
+					continue;
+				SuspendThread(pOpenThread);
+				CloseHandle(pOpenThread);
+			}
+		}
+		public static void Resume(this Process process)
+		{
+			foreach (ProcessThread thread in process.Threads)
+			{
+				var pOpenThread = OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint)thread.Id);
+				if (pOpenThread == IntPtr.Zero)
+					continue;
+				ResumeThread(pOpenThread);
+				CloseHandle(pOpenThread);
+			}
+		}
+	}
+}
diff --git a/TGServerService/TGServerService.csproj b/TGServerService/TGServerService.csproj
index b5a28de59e..55d8dbed62 100644
--- a/TGServerService/TGServerService.csproj
+++ b/TGServerService/TGServerService.csproj
@@ -92,6 +92,7 @@
     <Compile Include="InterfaceBase.cs" />
     <Compile Include="IRC.cs" />
     <Compile Include="Interop.cs" />
+    <Compile Include="ProcessExtension.cs" />
     <Compile Include="Properties\Settings.Designer.cs">
       <AutoGen>True</AutoGen>
       <DesignTimeSharedInput>True</DesignTimeSharedInput>