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目录
引言
Android系统服务启动顺序
zygote fork SystemServer 进程
SystemServer启动流程
1、SystemServer.main()
2、SystemServer.run()
3、初始化系统上下文
4、创建系统服务管理
5、启动系统各种服务
总结
引言
开机启动时 PowerManagerService 调用 AudioService 音频接口可能会导致 JE 崩溃，进而 system_server 崩溃。
分析：应该和系统服务SystemServer启动的顺序有关
Android系统服务启动顺序
Android整体启动流程概括为：启动BootLoader->加载系统内核->启动Init进程->启动Zygote进程->启动Runtime进程->启动本地服务->启动Home Launcher
SystemServer 服务进程是 Android 系统 Java 层框架的核心，它维护着 Android 系统的 核心服务，比如：ActivityManagerService、WindowManagerService、PackageManagerService 等，是 Android 系统中一个非常重要的进程。在 Android 系统中，应用程序出现问题，对系统影响不大，而 Init、Zygote、SystemServer 三大进程对系统的影响则非常大，因为其中任何一个 crash，都会造成系统崩溃，出现重启现象。
zygote fork SystemServer 进程
SystemServer 是由 Zygote 孵化而来的一个进程，通过 ps 命令，我们发现其进程名为：system_server。在分析 zygote 进程时，我们知道当 zygote 进程进入到 java 世界后，在 ZygoteInit.java 中，将调用 forkSystemServer 方法启动 SystemServer 进程。
// frameworks/base/core/java/com/android/internal/os/ZygoteInit.javapublic class ZygoteInit {public static void main(String argv[]) {try {if (startSystemServer) {// fork 出 system_serverRunnable r = forkSystemServer(abiList, zygoteSocketName, zygoteServer);if (r != null) {r.run();return;}}}}private static Runnable forkSystemServer(String abiList, String socketName,ZygoteServer zygoteServer) {try {... .../* Request to fork the system server process */pid = Zygote.forkSystemServer(parsedArgs.mUid, parsedArgs.mGid,parsedArgs.mGids,parsedArgs.mRuntimeFlags,null,parsedArgs.mPermittedCapabilities,parsedArgs.mEffectiveCapabilities);} catch (IllegalArgumentException ex) {throw new RuntimeException(ex);}}}......
SystemServer启动流程
1、SystemServer.main()
接下来就进到了 SystemServer.java 的 main() 函数处理流程：
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {/*** The main entry point from zygote.*/public static void main(String[] args) {new SystemServer().run(); // 创建并运行，简单粗暴！}}这里直接 new 出一个 SystemServer 对象 并执行其 run() 方法。
2、SystemServer.run()
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {private void run() {try {traceBeginAndSlog("InitBeforeStartServices");... ...// 如果系统时钟早于1970年，则设置系统始终从1970年开始if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {Slog.w(TAG, "System clock is before 1970; setting to 1970.");SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);}... ... if (!SystemProperties.get("persist.sys.language").isEmpty()) {// 设置区域，语言等选项 final String languageTag = Locale.getDefault().toLanguageTag();SystemProperties.set("persist.sys.locale", languageTag);SystemProperties.set("persist.sys.language", "");SystemProperties.set("persist.sys.country", "");SystemProperties.set("persist.sys.localevar", "");}... ...// 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(); // 设置堆栈利用率，GC 后会重新计算堆栈空间大小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); ... ...// 加载动态库 libandroid_services.soSystem.loadLibrary("android_servers"); // 检测上次关机过程是否失败，该方法可能不会返回performPendingShutdown(); // 在 SystemServer 进程中也需要创建 Context 对象，初始化系统上下文createSystemContext(); // 创建 SystemServiceManager 对象mSystemServiceManager = new SystemServiceManager(mSystemContext); // SystemServer 进程主要是用来构建系统各种 service 服务，// 而 SystemServiceManager 就是这些服务的管理对象 mSystemServiceManager.setStartInfo(mRuntimeRestart,mRuntimeStartElapsedTime, mRuntimeStartUptime); // 将 SystemServiceManager 对象保存到 SystemServer 进程中的一个数据结构中 LocalServices.addService(SystemServiceManager.class, mSystemServiceManager); // Prepare the thread pool for init tasks that can be parallelizedSystemServerInitThreadPool.get();} finally {traceEnd(); // InitBeforeStartServices}// Start services.try {traceBeginAndSlog("StartServices");startBootstrapServices(); // 主要用于启动系统 Boot 级服务 startCoreServices(); // 主要用于启动系统核心的服务 startOtherServices(); // 主要用于启动一些非紧要或者非需要及时启动的服务 } catch (Throwable ex) {Slog.e("System", "******************************************");Slog.e("System", "************ Failure starting system services", ex);throw ex;} finally {traceEnd();}... ...// 启动looper，以处理到来的消息，一直循环执行Looper.loop(); throw new RuntimeException("Main thread loop unexpectedly exited");}}以上就是 SystemServer.run() 方法的整个流程，简化如下
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {private void run() {try {// Initialize the system context.createSystemContext(); // 01. 初始化系统上下文// 02. 创建系统服务管理 mSystemServiceManager = new SystemServiceManager(mSystemContext);mSystemServiceManager.setRuntimeRestarted(mRuntimeRestart); LocalServices.addService(SystemServiceManager.class, mSystemServiceManager); } finally {traceEnd(); // InitBeforeStartServices}// 03.启动系统各种服务try {startBootstrapServices(); // 启动引导服务startCoreServices(); // 启动核心服务startOtherServices(); // 启动其他服务}// Loop forever.Looper.loop(); // 一直循环执行 throw new RuntimeException("Main thread loop unexpectedly exited");}}接下来我们针对 SystemServer 所做的 三部分工作 单独分析！
3、初始化系统上下文
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {private void createSystemContext() {ActivityThread activityThread = ActivityThread.systemMain();mSystemContext = activityThread.getSystemContext();mSystemContext.setTheme(DEFAULT_SYSTEM_THEME);final Context systemUiContext = activityThread.getSystemUiContext();systemUiContext.setTheme(DEFAULT_SYSTEM_THEME);}}跟踪 systemMain() 方法
// frameworks/base/core/java/android/app/ActivityThread.javapublic final class ActivityThread extends ClientTransactionHandler {public static ActivityThread systemMain() {// The system process on low-memory devices do not get to use hardware// accelerated drawing, since this can add too much overhead to the// process.if (!ActivityManager.isHighEndGfx()) {ThreadedRenderer.disable(true); // 对于低内存的设备，禁用硬件加速} else {ThreadedRenderer.enableForegroundTrimming();}ActivityThread thread = new ActivityThread();thread.attach(true, 0); // 调用 attach() 方法return thread;}}跟踪 attach() 方法
// frameworks/base/core/java/android/app/ActivityThread.javapublic final class ActivityThread extends ClientTransactionHandler {private void attach(boolean system, long startSeq) {sCurrentActivityThread = this;mSystemThread = system;if (!system) {... ...} else {// Don't set application object here -- if the system crashes,// we can't display an alert, we just want to die die die.// 设置 SystemServer 进程在 DDMS 中显示的名字为 "system_process"android.ddm.DdmHandleAppName.setAppName("system_process",UserHandle.myUserId()); // 如不设置，则显示"?"，无法调试该进程try {mInstrumentation = new Instrumentation();mInstrumentation.basicInit(this);// 首先通过 getSystemContext() 创建系统上下文，然后创建应用上下文ContextImpl context = ContextImpl.createAppContext(this, getSystemContext().mPackageInfo);// 创建 ApplicationmInitialApplication = context.mPackageInfo.makeApplication(true, null);// 调用 Application的 onCreate()mInitialApplication.onCreate();} catch (Exception e) {throw new RuntimeException("Unable to instantiate Application():" + e.toString(), e);} }... ...ViewRootImpl.ConfigChangedCallback configChangedCallback= (Configuration globalConfig) -> {synchronized (mResourcesManager) {// We need to apply this change to the resources immediately, because upon returning// the view hierarchy will be informed about it.if (mResourcesManager.applyConfigurationToResourcesLocked(globalConfig,null /* compat */)) {updateLocaleListFromAppContext(mInitialApplication.getApplicationContext(),mResourcesManager.getConfiguration().getLocales());// This actually changed the resources! Tell everyone about it.if (mPendingConfiguration == null|| mPendingConfiguration.isOtherSeqNewer(globalConfig)) {mPendingConfiguration = globalConfig;sendMessage(H.CONFIGURATION_CHANGED, globalConfig);}}}};// 添加回调ViewRootImpl.addConfigCallback(configChangedCallback); }}我们发现 attach() 方法主要做了四件事：
（1）创建系统上下文：getSystemContext()；
（2）创建应用上下文：createAppContext()；
（3）创建 Application：makeApplication()；
（4）添加回调 configChangedCallback 到 ViewRootImpl。
（1）创建系统上下文
// frameworks/base/core/java/android/app/ActivityThread.javapublic final class ActivityThread extends ClientTransactionHandler {public ContextImpl getSystemContext() {synchronized (this) {if (mSystemContext == null) {mSystemContext = ContextImpl.createSystemContext(this);}return mSystemContext;}}}// frameworks/base/core/java/android/app/ContextImpl.javaclass ContextImpl extends Context {static ContextImpl createSystemContext(ActivityThread mainThread) {// 这边 new 出来的 LoadedApk 将作为创建应用上下文的参数 packageInfoLoadedApk packageInfo = new LoadedApk(mainThread);// ContextImpl() 创建系统上下文 ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, 0,null, null);context.setResources(packageInfo.getResources());context.mResources.updateConfiguration(context.mResourcesManager.getConfiguration(),context.mResourcesManager.getDisplayMetrics());return context;}}（2）创建应用上下文
// frameworks/base/core/java/android/app/ContextImpl.javaclass ContextImpl extends Context {static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo) {return createAppContext(mainThread, packageInfo, null);}static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo,String opPackageName) {if (packageInfo == null) throw new IllegalArgumentException("packageInfo");// ContextImpl()创建应用上下文ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, 0,null, opPackageName);context.setResources(packageInfo.getResources());return context;}}我们可以看出：new ContextImpl() 时，系统上下文和应用上下文的参数是一样的，createAppContext() 中的参数 packageInfo，就是 createSystemContext() 中 new 的 LoadedApk。
创建完成之后，系统上下文赋值给了 ActivityThread 的成员变量 mSystemContext，而应用上下文只是作为函数中的局部变量临时使用。
（3）创建 Application
// frameworks/base/core/java/android/app/LoadedApk.javapublic final class LoadedApk {public Application makeApplication(boolean forceDefaultAppClass,Instrumentation instrumentation) {if (mApplication != null) {return mApplication;}Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "makeApplication");Application app = null;String appClass = mApplicationInfo.className;if (forceDefaultAppClass || (appClass == null)) { // forceDefaultAppClass 为 true appClass = "android.app.Application";}try {java.lang.ClassLoader cl = getClassLoader();// 此 LoadedApk 对象是 createSystemContext 时 new 的，mPackageName = "android"if (!mPackageName.equals("android")) { initializeJavaContextClassLoader();}// 又创建了一个局部应用上下文ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this); // 创建 Application app = mActivityThread.mInstrumentation.newApplication(cl, appClass, appContext);appContext.setOuterContext(app);} catch (Exception e) {if (!mActivityThread.mInstrumentation.onException(app, e)) {Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);throw new RuntimeException("Unable to instantiate application " + appClass+ ": " + e.toString(), e);}}// 将前面创建的 app 添加到应用列表mActivityThread.mAllApplications.add(app);mApplication = app;... ...Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);return app;}}4、创建系统服务管理
回顾下创建系统服务管理相关代码：
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {private void run() {try {// Initialize the system context.createSystemContext(); // 01. 初始化系统上下文// 02. 创建系统服务管理 mSystemServiceManager = new SystemServiceManager(mSystemContext);mSystemServiceManager.setRuntimeRestarted(mRuntimeRestart); LocalServices.addService(SystemServiceManager.class, mSystemServiceManager); } finally {traceEnd(); // InitBeforeStartServices}... ...}这一步只是 new 了一个 SystemServiceManager，并将其添加到本地服务列表中。mSystemContext 为第一步中创建的系统上下文。本地服务列表是以类为 key 保存的一个列表，即列表中某种类型的对象最多只能有一个。
new SystemServiceManager()
// frameworks/base/services/core/java/com/android/server/SystemServiceManager.javapublic class SystemServiceManager {... ...// 系统服务列表，系统服务必须继承 SystemServiceprivate final ArrayList<SystemService> mServices = new ArrayList<SystemService>();// 当前处于开机过程的哪个阶段private int mCurrentPhase = -1;SystemServiceManager(Context context) {mContext = context;}@SuppressWarnings("unchecked")// 通过类名启动系统服务，可能会找不到类而抛异常public SystemService startService(String className) {final Class<SystemService> serviceClass;try {serviceClass = (Class<SystemService>)Class.forName(className);} catch (ClassNotFoundException ex) {Slog.i(TAG, "Starting " + className);throw new RuntimeException("Failed to create service " + className+ ": service class not found, usually indicates that the caller should "+ "have called PackageManager.hasSystemFeature() to check whether the "+ "feature is available on this device before trying to start the "+ "services that implement it", ex);}return startService(serviceClass);}@SuppressWarnings("unchecked")// 创建并启动系统服务，系统服务类必须继承 SystemServicepublic <T extends SystemService> T startService(Class<T> serviceClass) {try {final String name = serviceClass.getName();Slog.i(TAG, "Starting " + name);Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);// Create the service.if (!SystemService.class.isAssignableFrom(serviceClass)) {throw new RuntimeException("Failed to create " + name+ ": service must extend " + SystemService.class.getName());}final T service;try {Constructor<T> constructor = serviceClass.getConstructor(Context.class);service = constructor.newInstance(mContext);} catch (InstantiationException ex) {... ...}startService(service);return service;} finally {Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);}}public void startService(@NonNull final SystemService service) {// Register it.mServices.add(service);// Start it.long time = SystemClock.elapsedRealtime();try {service.onStart();} catch (RuntimeException ex) {throw new RuntimeException("Failed to start service " + service.getClass().getName()+ ": onStart threw an exception", ex);}warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");}// 通知系统服务到了开机的哪个阶段，会遍历调用所有系统服务的 onBootPhase() 函数public void startBootPhase(final int phase) {... ...try {Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "OnBootPhase " + phase);final int serviceLen = mServices.size();for (int i = 0; i < serviceLen; i++) {final SystemService service = mServices.get(i);long time = SystemClock.elapsedRealtime();Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, service.getClass().getName());try {service.onBootPhase(mCurrentPhase);} catch (Exception ex) {throw new RuntimeException("Failed to boot service "+ service.getClass().getName()+ ": onBootPhase threw an exception during phase "+ mCurrentPhase, ex);}warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onBootPhase");Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);}} finally {Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);}}}5、启动系统各种服务
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {private void run() {// 01. 初始化系统上下文// 02. 创建系统服务管理 // 03.启动系统各种服务try {startBootstrapServices(); // 启动引导服务startCoreServices(); // 启动核心服务startOtherServices(); // 启动其他服务}// Loop forever.Looper.loop(); // 一直循环执行 throw new RuntimeException("Main thread loop unexpectedly exited");}}（1）启动引导服务startBootstrapServices()
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {/*** Starts the small tangle of critical services that are needed to get the system off the* ground. These services have complex mutual dependencies which is why we initialize them all* in one place here. Unless your service is also entwined in these dependencies, it should be* initialized in one of the other functions.*/private void startBootstrapServices() {... ...// 启动 Installer 服务，阻塞等待与 installd 建立 socket 通道Installer installer = mSystemServiceManager.startService(Installer.class);mSystemServiceManager.startService(DeviceIdentifiersPolicyService.class);mSystemServiceManager.startService(UriGrantsManagerService.Lifecycle.class);// 启动 ActivityManagerServiceActivityTaskManagerService atm = mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();mActivityManagerService.setSystemServiceManager(mSystemServiceManager);mActivityManagerService.setInstaller(installer);mWindowManagerGlobalLock = atm.getGlobalLock();// 启动 PowerManagerServicemPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);mSystemServiceManager.startService(ThermalManagerService.class);// PowerManagerService 就绪，AMS 初始化电源管理mActivityManagerService.initPowerManagement();mActivityManagerService.initPowerManagement();mSystemServiceManager.startService(RecoverySystemService.class);RescueParty.noteBoot(mSystemContext);// 启动 LightsServicemSystemServiceManager.startService(LightsService.class);// 启动 DisplayManagerServicemDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);// We need the default display before we can initialize the package manager.mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);// 当设备正在加密时，仅运行核心应用String cryptState = SystemProperties.get("vold.decrypt");if (ENCRYPTING_STATE.equals(cryptState)) {Slog.w(TAG, "Detected encryption in progress - only parsing core apps");mOnlyCore = true;} else if (ENCRYPTED_STATE.equals(cryptState)) {Slog.w(TAG, "Device encrypted - only parsing core apps");mOnlyCore = true;}// Start the package manager.if (!mRuntimeRestart) {MetricsLogger.histogram(null, "boot_package_manager_init_start",(int) SystemClock.elapsedRealtime());}// 启动 PackageManagerServicetry {Watchdog.getInstance().pauseWatchingCurrentThread("packagemanagermain");mPackageManagerService = PackageManagerService.main(mSystemContext, installer,mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);} finally {Watchdog.getInstance().resumeWatchingCurrentThread("packagemanagermain");}mFirstBoot = mPackageManagerService.isFirstBoot();mPackageManager = mSystemContext.getPackageManager();... ...// 将 UserManagerService 添加到服务列表，该服务是在 PackageManagerService 中初始化的 mSystemServiceManager.startService(UserManagerService.LifeCycle.class);// 初始化用来缓存包资源的属性缓存AttributeCache.init(mSystemContext);// Set up the Application instance for the system process and get started.mActivityManagerService.setSystemProcess();... ...mSensorServiceStart = SystemServerInitThreadPool.get().submit(() -> {TimingsTraceLog traceLog = new TimingsTraceLog(SYSTEM_SERVER_TIMING_ASYNC_TAG, Trace.TRACE_TAG_SYSTEM_SERVER);traceLog.traceBegin(START_SENSOR_SERVICE);startSensorService(); // 启动传感器服务traceLog.traceEnd();}, START_SENSOR_SERVICE);}}首先等待 installd 启动完成，然后启动一些相互依赖的关键服务。
（2）启动核心服务startCoreServices()
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {/*** Starts some essential services that are not tangled up in the bootstrap process.*/private void startCoreServices() {// 启动 BatteryService，用于统计电池电量，需要 LightServicemSystemServiceManager.startService(BatteryService.class);// 启动 UsageStatsService，用于统计应用使用情况mSystemServiceManager.startService(UsageStatsService.class);mActivityManagerService.setUsageStatsManager(LocalServices.getService(UsageStatsManagerInternal.class));// 启动 WebViewUpdateServiceif (mPackageManager.hasSystemFeature(PackageManager.FEATURE_WEBVIEW)) {mWebViewUpdateService = mSystemServiceManager.startService(WebViewUpdateService.class);}.... ...}}（3）启动其他服务startOtherServices()
代码很长（1200多行...），但是逻辑简单，主要是启动各种服务。
// frameworks/base/services/java/com/android/server/SystemServer.javapublic final class SystemServer {/*** Starts a miscellaneous grab bag of stuff that has yet to be refactored and organized.*/private void startOtherServices() {... ...try {... ...// 调度策略ServiceManager.addService("scheduling_policy", new SchedulingPolicyService());mSystemServiceManager.startService(TelecomLoaderService.class);// 提供电话注册、管理服务，可以获取电话的链接状态、信号强度等telephonyRegistry = new TelephonyRegistry(context);ServiceManager.addService("telephony.registry", telephonyRegistry);mEntropyMixer = new EntropyMixer(context);mContentResolver = context.getContentResolver();// 提供所有账号、密码、认证管理等等的服务mSystemServiceManager.startService(ACCOUNT_SERVICE_CLASS);... ...// 振动器服务vibrator = new VibratorService(context);ServiceManager.addService("vibrator", vibrator);... ...inputManager = new InputManagerService(context);// WMS needs sensor service readyConcurrentUtils.waitForFutureNoInterrupt(mSensorServiceStart, START_SENSOR_SERVICE);mSensorServiceStart = null;wm = WindowManagerService.main(context, inputManager, !mFirstBoot, mOnlyCore,new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false,DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PROTO);ServiceManager.addService(Context.INPUT_SERVICE, inputManager,/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);... ...} catch (RuntimeException e) {Slog.e("System", "******************************************");Slog.e("System", "************ Failure starting core service", e);}... ...LockSettingsService // 屏幕锁定服务，管理每个用户的相关锁屏信息DeviceIdleController // Doze模式的主要驱动DevicePolicyManagerService // 提供一些系统级别的设置及属性StatusBarManagerService // 状态栏管理服务ClipboardService // 系统剪切板服务NetworkManagementService // 网络管理服务TextServicesManagerService // 文本服务，例如文本检查等NetworkScoreService // 网络评分服务NetworkStatsService // 网络状态服务NetworkPolicyManagerService // 网络策略服务WifiP2pService // Wifi Direct服务WifiService // Wifi服务WifiScanningService // Wifi扫描服务RttService // Wifi相关EthernetService // 以太网服务ConnectivityService // 网络连接管理服务NsdService // 网络发现服务NotificationManagerService // 通知栏管理服务DeviceStorageMonitorService // 磁盘空间状态检测服务LocationManagerService // 位置服务，GPS、定位等CountryDetectorService // 检测用户国家SearchManagerService // 搜索管理服务DropBoxManagerService // 用于系统运行时日志的存储于管理WallpaperManagerService // 壁纸管理服务AudioService // AudioFlinger的上层管理封装，主要是音量、音效、声道及铃声等的管理DockObserver // 如果系统有个座子，当手机装上或拔出这个座子的话，就得靠他来管理了WiredAccessoryManager // 监视手机和底座上的耳机UsbService // USB服务SerialService // 串口服务TwilightService // 指出用户当前所在位置是否为晚上，被 UiModeManager 等用来调整夜间模式BackupManagerService // 备份服务AppWidgetService // 提供Widget的管理和相关服务VoiceInteractionManagerService // 语音交互管理服务DiskStatsService // 磁盘统计服务，供dumpsys使用SamplingProfilerService // 用于耗时统计等NetworkTimeUpdateService // 监视网络时间，当网络时间变化时更新本地时间。CertBlacklister // 提供一种机制更新SSL certificate blacklistDreamManagerService // 屏幕保护PrintManagerService // 打印服务HdmiControlService // HDMI控制服务FingerprintService // 指纹服务... ...}}总结
可以看到PowerManagerService先于AudioService启动，此时如果在PowerManagerService启动后立刻调用AudioService中的接口就会引发 JE 崩溃，进而导致system_server崩溃。