Fix control pipe accept loop: create instances only after a client connects; CLI force-update never touches the service log file

cmd/gpu-turnstile/main.go

@@ -362,6 +362,10 @@ func forceUpdateCommand(configPath string, elevatedChild bool) int {
 		fmt.Fprintf(os.Stderr, "gpu-turnstile: cannot locate executable: %v\n", err)
 		return 1
 	}
+	// One-shot CLI: the updater logs to stderr, never to the service's
+	// LOG_FILE — that file is ACL'd to the service account, and a CLI run
+	// has nothing worth persisting there.
+	cfg.LogFile = ""
 	log, _, logCloser := newLogger(cfg)
 	defer logCloser.Close()
 	if cfg.AppVersion == "dev" {

internal/control/control_windows.go

@@ -77,18 +77,16 @@ func Serve(ctx context.Context, h Handler, log *slog.Logger) error {
 				log.Warn("control channel stopped", "err", err)
 				return
 			}
-			go func() {
-				// Blocks until a client connects; on process exit the
-				// handle goes away with everything else. A client that
-				// raced us and connected between CreateNamedPipe and
-				// ConnectNamedPipe reports ERROR_PIPE_CONNECTED — that is
-				// a success, not a failure.
+			// Blocks until a client connects — only then is the next
+			// instance created, so instances are not burned without
+			// clients. ERROR_PIPE_CONNECTED means the client raced us
+			// and connected before the call: that is a success. Process
+			// exit reaps the blocked call on shutdown.
 			if err := windows.ConnectNamedPipe(pipe, nil); err != nil && err != errnoPipeConnected {
 				windows.CloseHandle(pipe)
-					return
+				continue
 			}
-				serveConn(&pipeConn{f: os.NewFile(uintptr(pipe), pipePath), h: pipe}, h)
-			}()
+			go serveConn(&pipeConn{f: os.NewFile(uintptr(pipe), pipePath), h: pipe}, h)
 		}
 	}()
 	return nil