DisposeAndNullControllers from a locked context

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

@@ -192,7 +192,7 @@ namespace Tgstation.Server.Host.Components.Watchdog
 			};
 
 		/// <inheritdoc />
-		protected override void DisposeAndNullControllers()
+		protected override void DisposeAndNullControllersImpl()
 		{
 			Server?.Dispose();
 			Server = null;

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

@@ -392,10 +392,8 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		}
 #pragma warning restore CA1502
 
-		/// <summary>
-		/// Call <see cref="IDisposable.Dispose"/> on <see cref="alphaServer"/> and <see cref="bravoServer"/> and set them to <see langword="null"/>
-		/// </summary>
-		protected override void DisposeAndNullControllers()
+		/// <inheritdoc />
+		protected override void DisposeAndNullControllersImpl()
 		{
 			alphaServer?.Dispose();
 			alphaServer = null;

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

@@ -112,6 +112,11 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		/// </summary>
 		readonly IRestartRegistration restartRegistration;
 
+		/// <summary>
+		/// <see langword="lock"/> <see cref="object"/> used for <see cref="DisposeAndNullControllers"/>.
+		/// </summary>
+		readonly object controllerDisposeLock;
+
 		/// <summary>
 		/// If the <see cref="WatchdogBase"/> should <see cref="LaunchImplNoLock(bool, bool, DualReattachInformation, CancellationToken)"/> in <see cref="StartAsync(CancellationToken)"/>
 		/// </summary>
@@ -201,6 +206,7 @@ namespace Tgstation.Server.Host.Components.Watchdog
 			ActiveLaunchParameters = initialLaunchParameters;
 			releaseServers = false;
 			ActiveParametersUpdated = new TaskCompletionSource<object>();
+			controllerDisposeLock = new object();
 
 			restartRegistration = serverControl.RegisterForRestart(this);
 			try
@@ -463,7 +469,16 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		/// <summary>
 		/// Call <see cref="IDisposable.Dispose"/> and null the fields for all <see cref="ISessionController"/>s and set <see cref="Running"/> to <see langword="false"/>.
 		/// </summary>
-		protected abstract void DisposeAndNullControllers();
+		protected abstract void DisposeAndNullControllersImpl();
+
+		/// <summary>
+		/// Wrapper for <see cref="DisposeAndNullControllersImpl"/> under a locked context.
+		/// </summary>
+		protected void DisposeAndNullControllers()
+		{
+			lock (controllerDisposeLock)
+				DisposeAndNullControllersImpl();
+		}
 
 		/// <summary>
 		/// Get the active <see cref="ISessionController"/>.

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

@@ -101,9 +101,9 @@ namespace Tgstation.Server.Host.Components.Watchdog
 		}
 
 		/// <inheritdoc />
-		protected override void DisposeAndNullControllers()
+		protected override void DisposeAndNullControllersImpl()
 		{
-			base.DisposeAndNullControllers();
+			base.DisposeAndNullControllersImpl();
 
 			// If we reach this point, we can guarantee PrepServerForLaunch will be called before starting again.
 			activeSwappable = null;