/**
     * The main entry point from zygote.
     */
    public static void main(String[] args) {
        new SystemServer().run();
    }

 private void run() {
        try {
           
	        // 如果当前系统时间比 1970 年更早，就设置当前系统时间为 1970 年
            if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
                Slog.w(TAG, "System clock is before 1970; setting to 1970.");
                SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
            }

        
            // Here we go!
            Slog.i(TAG, "Entered the Android system server!");
            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, SystemClock.uptimeMillis());

            // Ensure binder calls into the system always run at foreground priority.
            // 确保当前系统进程的 binder 调用，总是运行在前台优先级
            BinderInternal.disableBackgroundScheduling(true);

            // Prepare the main looper thread (this thread).
            android.os.Process.setThreadPriority(
                android.os.Process.THREAD_PRIORITY_FOREGROUND);
            android.os.Process.setCanSelfBackground(false);
            
            Looper.prepareMainLooper();

            // Initialize native services.加载本地服务
            System.loadLibrary("android_servers");

            // Check whether we failed to shut down last time we tried.
            // This call may not return.
            performPendingShutdown();

            // Initialize the system context.初始化系统上下文
            createSystemContext();

            // Create the system service manager.创建系统服务管理
            mSystemServiceManager = new SystemServiceManager(mSystemContext);
            // 将 mSystemServiceManager 添加到本地服务 LocalServices 的成员 sLocalServiceObjects
            LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
        }

        // Start services.
        try {
            Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartServices");
            // 启动服务代码
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
        }

        // Loop forever.
        Looper.loop();
        throw new RuntimeException("Main thread loop unexpectedly exited");
    }

       ServiceManager.addService("scheduling_policy", new SchedulingPolicyService());
       Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
       mSystemServiceManager.startService(TelecomLoaderService.class);

 /**
     * Publish the service so it is accessible to other services and apps.
     */
    protected final void publishBinderService(String name, IBinder service) {
        publishBinderService(name, service, false);
    }

    /**
     * Publish the service so it is accessible to other services and apps.
     */
    protected final void publishBinderService(String name, IBinder service,
            boolean allowIsolated) {
        ServiceManager.addService(name, service, allowIsolated);
    }

/**
     * Place a new @a service called @a name into the service
     * manager.
     * 
     * @param name the name of the new service
     * @param service the service object
     * @param allowIsolated set to true to allow isolated sandboxed processes
     * to access this service
     */
    public static void addService(String name, IBinder service, boolean allowIsolated) {
        try {
            getIServiceManager().addService(name, service, allowIsolated);
        } catch (RemoteException e) {
            Log.e(TAG, "error in addService", e);
        }
    }

service servicemanager /system/bin/servicemanager
    class core
    user system
    group system
    critical
    onrestart restart healthd
    onrestart restart zygote
    onrestart restart media
    onrestart restart surfaceflinger
    onrestart restart drm