Add TGS3 style process suspend/resume while swapping

src/Tgstation.Server.Host/Components/Repository/Repository.cs

@@ -130,11 +130,12 @@ namespace Tgstation.Server.Host.Components.Repository
 				if (disposed)
 					return;
 
-				logger.LogTrace("Disposing...");
 				disposed = true;
-				repository.Dispose();
-				onDispose();
 			}
+
+			logger.LogTrace("Disposing...");
+			repository.Dispose();
+			onDispose();
 		}
 
 		void GetRepositoryOwnerName(string remote, out string owner, out string name)

src/Tgstation.Server.Host/Components/Watchdog/SessionController.cs

@@ -549,6 +549,12 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		/// <inheritdoc />
 		public void SetHighPriority() => process.SetHighPriority();
 
+		/// <inheritdoc />
+		public void Suspend() => process.Suspend();
+
+		/// <inheritdoc />
+		public void Resume() => process.Resume();
+
 		/// <inheritdoc />
 		public void ReplaceDmbProvider(IDmbProvider dmbProvider)
 		{

src/Tgstation.Server.Host/Components/Watchdog/WindowsWatchdog.cs

@@ -120,7 +120,6 @@ namespace Tgstation.Server.Host.Components.Watchdog
 			if (pendingSwappable != null)
 			{
 				Logger.LogTrace("Replacing activeSwappable with pendingSwappable");
-
 				Server.ReplaceDmbProvider(pendingSwappable);
 				activeSwappable = pendingSwappable;
 				pendingSwappable = null;
@@ -139,7 +138,9 @@ namespace Tgstation.Server.Host.Components.Watchdog
 				windowsProvider = new WindowsSwappableDmbProvider(compileJobProvider, ioManager, symlinkFactory);
 
 				Logger.LogDebug("Swapping to compile job {0}...", windowsProvider.CompileJob.Id);
+				Server.Suspend();
 				await windowsProvider.MakeActive(cancellationToken).ConfigureAwait(false);
+				Server.Resume();
 			}
 			catch
 			{

src/Tgstation.Server.Host/NativeMethods.cs

@@ -24,6 +24,14 @@ namespace Tgstation.Server.Host
 			AllowUnprivilegedCreate = 2
 		}
 
+		/// <summary>
+		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686769(v=vs.85).aspx
+		/// </summary>
+		public enum ThreadAccess : int
+		{
+			SuspendResume = 0x0002,
+		}
+
 		/// <summary>
 		/// See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getwindowthreadprocessid
 		/// </summary>
@@ -70,5 +78,29 @@ namespace Tgstation.Server.Host
 		/// </summary>
 		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
 		public static extern bool CreateSymbolicLink(string lpSymlinkFileName, string lpTargetFileName, CreateSymbolicLinkFlags dwFlags);
+
+		/// <summary>
+		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms684335(v=vs.85).aspx
+		/// </summary>
+		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+		public static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);
+
+		/// <summary>
+		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms724211(v=vs.85).aspx
+		/// </summary>
+		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+		public static extern bool CloseHandle(IntPtr hObject);
+
+		/// <summary>
+		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms686345(v=vs.85).aspx
+		/// </summary>
+		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+		public static extern uint SuspendThread(IntPtr hThread);
+
+		/// <summary>
+		/// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms685086(v=vs.85).aspx
+		/// </summary>
+		[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+		public static extern uint ResumeThread(IntPtr hThread);
 	}
 }

src/Tgstation.Server.Host/System/IProcessBase.cs

@@ -17,5 +17,15 @@ namespace Tgstation.Server.Host.System
 		/// Set's the owned <see cref="global::System.Diagnostics.Process.PriorityClass"/> to <see cref="global::System.Diagnostics.ProcessPriorityClass.AboveNormal"/>
 		/// </summary>
 		void SetHighPriority();
+
+		/// <summary>
+		/// Suspends the process.
+		/// </summary>
+		void Suspend();
+
+		/// <summary>
+		/// Resumes the process.
+		/// </summary>
+		void Resume();
 	}
 }

src/Tgstation.Server.Host/System/Process.cs

@@ -1,5 +1,7 @@
-using Microsoft.Extensions.Logging;
+using BetterWin32Errors;
+using Microsoft.Extensions.Logging;
 using System;
+using System.Diagnostics;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -133,13 +135,65 @@ namespace Tgstation.Server.Host.System
 		{
 			try
 			{
-				handle.PriorityClass = global::System.Diagnostics.ProcessPriorityClass.AboveNormal;
-				logger.LogTrace("Set to above normal priority", handle.Id);
+				handle.PriorityClass = ProcessPriorityClass.AboveNormal;
+				logger.LogTrace("Set PID {0} to above normal priority", Id);
 			}
 			catch (Exception e)
 			{
 				logger.LogWarning("Unable to raise process priority! Exception: {0}", e);
 			}
 		}
+
+		/// <inheritdoc />
+		public void Suspend()
+		{
+			try
+			{
+				foreach (ProcessThread thread in handle.Threads)
+				{
+					var pOpenThread = NativeMethods.OpenThread(NativeMethods.ThreadAccess.SuspendResume, false, (uint)thread.Id);
+					if (pOpenThread == IntPtr.Zero)
+						continue;
+
+					if (NativeMethods.SuspendThread(pOpenThread) == UInt32.MaxValue)
+						throw new Win32Exception();
+
+					NativeMethods.CloseHandle(pOpenThread);
+				}
+
+				logger.LogTrace("Suspended PID {0}", Id);
+			}
+			catch (Exception e)
+			{
+				logger.LogError(e, "Failed to suspend PID {0}!", Id);
+				throw;
+			}
+		}
+
+		/// <inheritdoc />
+		public void Resume()
+		{
+			try
+			{
+				foreach (ProcessThread thread in handle.Threads)
+				{
+					var pOpenThread = NativeMethods.OpenThread(NativeMethods.ThreadAccess.SuspendResume, false, (uint)thread.Id);
+					if (pOpenThread == IntPtr.Zero)
+						continue;
+
+					if (NativeMethods.ResumeThread(pOpenThread) == UInt32.MaxValue)
+						throw new Win32Exception();
+
+					NativeMethods.CloseHandle(pOpenThread);
+				}
+
+				logger.LogTrace("Resumed PID {0}", Id);
+			}
+			catch (Exception e)
+			{
+				logger.LogError(e, "Failed to resume PID {0}!", Id);
+				throw;
+			}
+		}
 	}
 }