Android系统启动-SystemServer下篇_app

概述copyfrom：http://gityuan.com/2016/02/20/android-system-server-2/ 基于Android6.0的源码剖析，分析Android启动过程的system_server进程frameworks/base/services/java/com/android/server/-SystemServer.javaframeworks/base/services/core/java/com/android/se

copy from ：http://gityuan.com/2016/02/20/android-system-server-2/

基于AndroID 6.0的源码剖析，分析AndroID启动过程的system_server进程

frameworks/base/services/java/com/androID/server/  - SystemServer.javaframeworks/base/services/core/java/com/androID/server/  - SystemServiceManager.java  - ServiceThread.java  - am/ActivityManagerService.javaframeworks/base/core/java/androID/app/  - ActivityThread.java  - LoadedApk.java  - ContextImpl.java

一. SystemServer启动

上篇文章Android系统启动-systemServer上篇从Zygote一路启动到SystemServer的过程。简单回顾下，在RuntimeInit.java中invokeStaticMain方法通过创建并抛出异常ZygoteInit.MethodAndArgsCaller，在ZygoteInit.java中的main()方法会捕捉该异常，并调用caller.run()，再通过反射便会调用到SystemServer.main()方法，该方法主要执行流程：

SystemServer.main    SystemServer.run        createSystemContext        startbootstrapServices();        startCoreServices();        startOtherServices();        Looper.loop();

接下来，从其main方法说起。

1.1 SystemServer.main

public final class SystemServer {    ...    public static voID main(String[] args) {        //先初始化SystemServer对象，再调用对象的run()方法， 【见小节1.2】        new SystemServer().run();    }}

1.2 SystemServer.run

private voID run() {    //当系统时间比1970年更早，就设置当前系统时间为1970年    if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {        SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);    }    //变更虚拟机的库文件，对于AndroID 6.0默认采用的是libart.so    SystemPropertIEs.set("persist.sys.dalvik.vm.lib.2", vmruntime.getRuntime().vmlibrary());    if (SamplingProfilerIntegration.isEnabled()) {        ...    }    //清除vm内存增长上限，由于启动过程需要较多的虚拟机内存空间    vmruntime.getRuntime().clearGrowthlimit();    //设置内存的可能有效使用率为0.8    vmruntime.getRuntime().setTargetHeaputilization(0.8f);    // 针对部分设备依赖于运行时就产生指纹信息，因此需要在开机完成前已经定义    Build.ensureFingerprintproperty();    //访问环境变量前，需要明确地指定用户    Environment.setUserrequired(true);    //确保当前系统进程的binder调用，总是运行在前台优先级(foreground priority)    BinderInternal.disableBackgroundScheduling(true);    androID.os.Process.setThreadPriority(androID.os.Process.THREAD_PRIORITY_FOREGROUND);    androID.os.Process.setCanSelfBackground(false);    // 主线程looper就在当前线程运行    Looper.prepareMainLooper();    //加载androID_servers.so库，该库包含的源码在frameworks/base/services/目录下    System.loadlibrary("androID_servers");    //检测上次关机过程是否失败，该方法可能不会返回[见小节1.2.1]    performPendingShutdown();    //初始化系统上下文 【见小节1.3】    createSystemContext();    //创建系统服务管理    mSystemServiceManager = new SystemServiceManager(mSystemContext);    //将mSystemServiceManager添加到本地服务的成员sLocalServiceObjects    LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);    //启动各种系统服务    try {        startbootstrapServices(); // 启动引导服务【见小节1.4】        startCoreServices();      // 启动核心服务【见小节1.5】        startOtherServices();     // 启动其他服务【见小节1.6】    } catch (Throwable ex) {        Slog.e("System", "************ Failure starting system services", ex);        throw ex;    }    //用于deBUG版本，将log事件不断循环地输出到dropBox（用于分析）    if (StrictMode.conditionallyEnableDeBUGLogging()) {        Slog.i(TAG, "Enabled StrictMode for system server main thread.");    }    //一直循环执行    Looper.loop();    throw new RuntimeException("Main thread loop unexpectedly exited");}

LocalServices通过用静态Map变量sLocalServiceObjects，来保存以服务类名为key，以具体服务对象为value的Map结构。

1.2.1 performPendingShutdown

[–>SystemServer.java]

private voID performPendingShutdown() {    final String shutdownAction = SystemPropertIEs.get(            ShutdownThread.SHUTDOWN_ACTION_PROPERTY, "");    if (shutdownAction != null && shutdownAction.length() > 0) {        boolean reboot = (shutdownAction.charat(0) == '1');        final String reason;        if (shutdownAction.length() > 1) {            reason = shutdownAction.substring(1, shutdownAction.length());        } else {            reason = null;        }        // 当"sys.shutdown.requested"值不为空,则会重启或者关机        ShutdownThread.rebootOrShutdown(null, reboot, reason);    }}

1.3 createSystemContext

[–>SystemServer.java]

private voID createSystemContext() {    //创建system_server进程的上下文信息    ActivityThread activityThread = ActivityThread.systemMain();    mSystemContext = activityThread.getSystemContext();    //设置主题    mSystemContext.settheme(androID.R.style.theme_DeviceDefault_light_DarkActionbar);}

理解Application创建过程已介绍过createSystemContext()过程，该过程会创建对象有ActivityThread，Instrumentation, ContextImpl，LoadedApk，Application。

1.4 startbootstrapServices

[–>SystemServer.java]

private voID startbootstrapServices() {    //阻塞等待与installd建立socket通道    Installer installer = mSystemServiceManager.startService(Installer.class);    //启动服务ActivityManagerService    mActivityManagerService = mSystemServiceManager.startService(            ActivityManagerService.lifecycle.class).getService();    mActivityManagerService.setSystemServiceManager(mSystemServiceManager);    mActivityManagerService.setInstaller(installer);    //启动服务PowerManagerService    mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);    //初始化power management    mActivityManagerService.initPowerManagement();    //启动服务lightsService    mSystemServiceManager.startService(lightsService.class);    //启动服务displayManagerService    mdisplayManagerService = mSystemServiceManager.startService(displayManagerService.class);    //Phase100: 在初始化package manager之前，需要默认的显示.    mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAulT_disPLAY);    //当设备正在加密时，仅运行核心    String cryptState = SystemPropertIEs.get("vold.decrypt");    if (ENCRYPTING_STATE.equals(cryptState)) {        mOnlyCore = true;    } else if (ENCRYPTED_STATE.equals(cryptState)) {        mOnlyCore = true;    }    //启动服务PackageManagerService    mPackageManagerService = PackageManagerService.main(mSystemContext, installer,            mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);    mFirstBoot = mPackageManagerService.isFirstBoot();    mPackageManager = mSystemContext.getPackageManager();    //启动服务UserManagerService，新建目录/data/user/    ServiceManager.addService(Context.USER_SERVICE, UserManagerService.getInstance());    AttributeCache.init(mSystemContext);    //设置AMS    mActivityManagerService.setSystemProcess();    //启动传感器服务    startSensorService();}

该方法所创建的服务：ActivityManagerService, PowerManagerService, lightsService, displayManagerService， PackageManagerService， UserManagerService， sensor服务.

1.5 startCoreServices

private voID startCoreServices() {    //启动服务BatteryService，用于统计电池电量，需要lightService.    mSystemServiceManager.startService(BatteryService.class);    //启动服务UsageStatsService，用于统计应用使用情况    mSystemServiceManager.startService(UsageStatsService.class);    mActivityManagerService.setUsageStatsManager(            LocalServices.getService(UsageStatsManagerInternal.class));    mPackageManagerService.getUsageStatsIfnopackageUsageInfo();    //启动服务WebVIEwUpdateService    mSystemServiceManager.startService(WebVIEwUpdateService.class);}

启动服务BatteryService，UsageStatsService，WebVIEwUpdateService。

1.6 startOtherServices

该方法比较长，有近千行代码，逻辑很简单，主要是启动一系列的服务，这里就不具体列举源码了，在第四节直接对其中的服务进行一个简单分类。

    private voID startOtherServices() {        ...        SystemConfig.getInstance();        mContentResolver = context.getContentResolver(); // resolver        ...        mActivityManagerService.installSystemProvIDers(); //provIDer        mSystemServiceManager.startService(AlarmManagerService.class); // alarm        // watchdog        watchdog.init(context, mActivityManagerService);         inputManager = new inputManagerService(context); // input        wm = WindowManagerService.main(...); // window        inputManager.start();  //启动input        mdisplayManagerService.windowManagerAndinputReady();        ...        mSystemServiceManager.startService(MOUNT_SERVICE_CLASS); // mount        mPackageManagerService.performBootDexOpt();  // dexopt *** 作        ActivityManagerNative.getDefault().showBootMessage(...); //显示启动界面        ...        statusbar = new StatusbarManagerService(context, wm); //statusbar        //dropBox        ServiceManager.addService(Context.DROPBox_SERVICE,                    new DropBoxManagerService(context, new file("/data/system/dropBox")));         mSystemServiceManager.startService(JobSchedulerService.class); //JobScheduler         lockSettings.systemReady(); //lockSettings        //phase480 和phase500        mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);        mSystemServiceManager.startBootPhase(SystemService.PHASE_SYstem_SERVICES_READY);        ...        // 准备好window, power, package, display服务        wm.systemReady();        mPowerManagerService.systemReady(...);        mPackageManagerService.systemReady();        mdisplayManagerService.systemReady(...);                //重头戏[见小节2.1]        mActivityManagerService.systemReady(new Runnable() {            public voID run() {              ...            }        });    }

SystemServer启动各种服务中最后的一个环节便是AMS.systemReady()，详见ActivityManagerService启动过程.

到此, System_server主线程的启动工作总算完成, 进入Looper.loop()状态,等待其他线程通过handler发送消息到主线再处理.

二、服务启动阶段

SystemServiceManager的startBootPhase()贯穿system_server进程的整个启动过程：

其中PHASE_BOOT_COMPLETED=1000，该阶段是发生在Boot完成和home应用启动完毕。系统服务更倾向于监听该阶段，而不是注册广播ACTION_BOOT_COMPLETED，从而降低系统延迟。

各个启动阶段所在源码的大致位置：

public final class SystemServer {    private voID startbootstrapServices() {      ...      //phase100      mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAulT_disPLAY);      ...    }    private voID startCoreServices() {      ...    }    private voID startOtherServices() {      ...      //phase480 && 500      mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);      mSystemServiceManager.startBootPhase(SystemService.PHASE_SYstem_SERVICES_READY);            ...      mActivityManagerService.systemReady(new Runnable() {         public voID run() {             //phase550             mSystemServiceManager.startBootPhase(                     SystemService.PHASE_ACTIVITY_MANAGER_READY);             ...             //phase600             mSystemServiceManager.startBootPhase(                     SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);          }      }    }}

接下来再说说简单每个阶段的大概完成的工作：

2.1 Phase0

创建四大引导服务:

ActivityManagerServicePowerManagerServicelightsServicedisplayManagerService2.2 Phase100

进入阶段PHASE_WAIT_FOR_DEFAulT_disPLAY=100回调服务

onBootPhase(100)

displayManagerService

然后创建大量服务下面列举部分:

PackageManagerServiceWindowManagerServiceinputManagerServiceNetworkManagerServiceDropBoxManagerServiceFingerprintServiceLauncherAppsService…2.3 Phase480

进入阶段PHASE_LOCK_SETTINGS_READY=480回调服务

onBootPhase(480)

DevicePolicyManagerService

阶段480后马上就进入阶段500.

2.4 Phase500

PHASE_SYstem_SERVICES_READY=500，进入该阶段服务能安全地调用核心系统服务.

onBootPhase(500)

AlarmManagerServiceJobSchedulerServicenotificationmanagerServicebackupmanagerServiceUsageStatsServicedeviceidleControllerTrustManagerService

UiModeManagerService

BluetoothServiceBluetoothManagerServiceEthernetServicewifip2pServiceWifiScanningServiceWifiServiceRttService

各大服务执行systemReady():

WindowManagerService.systemReady():PowerManagerService.systemReady():PackageManagerService.systemReady():displayManagerService.systemReady():

接下来就绪AMS.systemReady方法.

2.5 Phase550

PHASE_ACTIVITY_MANAGER_READY=550， AMS.mSystemReady=true, 已准备就绪,进入该阶段服务能广播Intent;但是system_server主线程并没有就绪.

onBootPhase(550)

MountServiceTelecomloaderServiceUsbServiceWebVIEwUpdateServiceDockObserverBatteryService

接下来执行: (AMS启动native crash监控, 加载WebVIEw，启动systemUI等),如下

mActivityManagerService.startObservingNativeCrashes();WebVIEwFactory.prepareWebVIEwInSystemServer();

startsystemUI(context);

networkscoreF.systemReady();networkManagementF.systemReady();networkStatsF.systemReady();networkPolicyF.systemReady();connectivityF.systemReady();audioServiceF.systemReady();Watchdog.getInstance().start();2.6 Phase600

PHASE_THIRD_PARTY_APPS_CAN_START=600

onBootPhase(600)

JobSchedulerServicenotificationmanagerServicebackupmanagerServiceAppWidgetServiceGestu@R_9_4404@erServiceDreamManagerServiceTrustManagerServiceVoiceInteractionManagerService

接下来,各种服务的systemRunning过程:

WallpaperManagerService、inputMethodManagerService、LocationManagerService、CountryDetectorService、NetworkTimeUpdateService、CommonTimeManagementService、TextServicesManagerService、AssetAtlasService、inputManagerService、TelephonyRegistry、MediaRouterService、MmsServicebroker这些服务依次执行其systemRunning()方法。

2.7 Phase1000

在经过一系列流程，再调用AMS.finishBooting()时，则进入阶段Phase1000。

到此，系统服务启动阶段完成就绪，system_server进程启动完成则进入Looper.loop()状态，随时待命，等待消息队列MessageQueue中的消息到来，则马上进入执行状态。

三、服务类别

system_server进程，从源码角度划分为引导服务、核心服务、其他服务3类。以下这些系统服务的注册过程, 见Android系统服务的注册方式

引导服务(7个)：ActivityManagerService、PowerManagerService、lightsService、displayManagerService、PackageManagerService、UserManagerService、SensorService；核心服务(3个)：BatteryService、UsageStatsService、WebVIEwUpdateService；其他服务(70个+)：AlarmManagerService、VibratorService等。

合计总大约80个系统服务：

`ActivityManagerService`	`PackageManagerService`	`WindowManagerService`
`PowerManagerService`	`BatteryService`	`BatteryStatsService`
`DreamManagerService`	`DropBoxManagerService`	`SamplingProfilerService`
`UsageStatsService`	`diskStatsService`	`DeviceStorageMonitorService`
SchedulingPolicyService	`AlarmManagerService`	deviceidleController
ThermalObserver	JobSchedulerService	`AccessibilityManagerService`
displayManagerService	lightsService	`GraphicsstatsService`
StatusbarManagerService	notificationmanagerService	WallpaperManagerService
UiModeManagerService	AppWidgetService	LauncherAppsService
TextServicesManagerService	ContentService	LockSettingsService
inputMethodManagerService	inputManagerService	`MountService`
FingerprintService	TvinputManagerService	DockObserver
NetworkManagementService	NetworkscoreService	`NetworkStatsService`
NetworkPolicyManagerService	ConnectivityService	BluetoothService
wifip2pService	WifiService	WifiScanningService
AudioService	MediaRouterService	VoiceInteractionManagerService
mediaprojectionmanagerService	MediaSessionService
DevicePolicyManagerService	PrintManagerService	`backupmanagerService`
`UserManagerService`	AccountManagerService	`TrustManagerService`
`SensorService`	LocationManagerService	VibratorService
CountryDetectorService	Gestu@R_9_4404@erService	PersistentDataBlockService
EthernetService	WebVIEwUpdateService	ClipboardService
TelephonyRegistry	TelecomloaderService	NsdService
UpdateLockService	SerialService	SearchManagerService
CommonTimeManagementService	AssetAtlasService	Consumerirservice
MidiserviceCameraService	TwilightService	RestrictionsManagerService
MmsServicebroker	RttService	UsbService