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一、system_server进程介绍
二、system_server进程启动流程
2.1 startBootstrapServices
2.2 startCoreServices
2.3 startOtherServices
2.4 startApexServices
三、如何使用系统服务
3.1 app进程调用系统服务
3.2 native进程调用系统服务
3.3 system_server进…目录
一、system_server进程介绍
二、system_server进程启动流程
2.1 startBootstrapServices
2.2 startCoreServices
2.3 startOtherServices
2.4 startApexServices
三、如何使用系统服务
3.1 app进程调用系统服务
3.2 native进程调用系统服务
3.3 system_server进程中两个服务之间的调用
四、如何添加一个系统服务
五、如何裁剪系统服务
六、其它模块
6.1 NativeCrashListener
6.2 Android watchdog 一、system_server进程介绍
Android system_server进程由zygote进程fork创建是framework层的核心进程主要由ASM、PMS等系统服务组成给app提供Binder调用、与native hal进程通信。
二、system_server进程启动流程
system_server进程启动入口
// frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
public static void main(String[] argv) {...if (startSystemServer) {Runnable r forkSystemServer(abiList, zygoteSocketName, zygoteServer);}...
}private static Runnable forkSystemServer(String abiList, String socketName,ZygoteServer zygoteServer) {...pid Zygote.forkSystemServer(parsedArgs.mUid, parsedArgs.mGid,parsedArgs.mGids,parsedArgs.mRuntimeFlags,null,parsedArgs.mPermittedCapabilities,parsedArgs.mEffectiveCapabilities);...
}// frameworks/base/core/java/com/android/internal/os/Zygote.java
static int forkSystemServer(int uid, int gid, int[] gids, int runtimeFlags,int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) {ZygoteHooks.preFork();int pid nativeForkSystemServer(uid, gid, gids, runtimeFlags, rlimits,permittedCapabilities, effectiveCapabilities);// Set the Java Language thread priority to the default value for new apps.Thread.currentThread().setPriority(Thread.NORM_PRIORITY);ZygoteHooks.postForkCommon();return pid;
}// frameworks/base/core/jni/com_android_internal_os_Zygote.cpp
static jint com_android_internal_os_Zygote_nativeForkSystemServer(JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,jint runtime_flags, jobjectArray rlimits, jlong permitted_capabilities,jlong effective_capabilities) {...// fork出system_server子进程pid_t pid zygote::ForkCommon(env, true, fds_to_close, fds_to_ignore, true);// 通过JNI调用SystemServer类的main方法if (pid 0) {SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits, permitted_capabilities,effective_capabilities, MOUNT_EXTERNAL_DEFAULT, nullptr, nullptr, true,false, nullptr, nullptr, /* is_top_app */ false,/* pkg_data_info_list */ nullptr,/* allowlisted_data_info_list */ nullptr, false, false);} else if (pid 0) {...}return pid;
}
通过JNI调用SystemServer类的main方法
// frameworks/base/services/java/com/android/server/SystemServer.java public static void main(String[] args) {...new SystemServer().run();
}private void run() {...// Start services.startBootstrapServices(t);startCoreServices(t);startOtherServices(t);startApexServices(t);updateWatchdogTimeout(t); ...
}
2.1 startBootstrapServices
启动系统最重要的服务执行startService和startBootPhase方法如下 // frameworks/base/services/java/com/android/server/SystemServer.java private void startBootstrapServices(NonNull TimingsTraceAndSlog t) {// 启动watchdog线程final Watchdog watchdog Watchdog.getInstance();watchdog.start();...// 启动AMSActivityTaskManagerService atm mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();mActivityManagerService ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);mActivityManagerService.setSystemServiceManager(mSystemServiceManager);mActivityManagerService.setInstaller(installer);mWindowManagerGlobalLock atm.getGlobalLock();// 启动PMSmPowerManagerService mSystemServiceManager.startService(PowerManagerService.class);// 启动ThermalManagerServicemSystemServiceManager.startService(ThermalManagerService.class);...mSystemServiceManager.startBootPhase(t, SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);}
startService通过反射的方式调用服务的onStart方法
// frameworks/base/services/core/java/com/android/server/SystemServiceManager.javapublic T extends SystemService T startService(ClassT serviceClass) {final String name serviceClass.getName();// 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 {ConstructorT constructor serviceClass.getConstructor(Context.class);service constructor.newInstance(mContext);}...startService(service);return service;
}public void startService(NonNull final SystemService service) {// Check if already startedString className service.getClass().getName();if (mServiceClassnames.contains(className)) {Slog.i(TAG, Not starting an already started service className);return;}mServiceClassnames.add(className);// Register it.mServices.add(service);// Start it.long time SystemClock.elapsedRealtime();try {service.onStart();}
}
PMS服务执行onStart和startBootPhase方法
public void onStart() {publishBinderService(Context.POWER_SERVICE, mBinderService, /* allowIsolated */ false,DUMP_FLAG_PRIORITY_DEFAULT | DUMP_FLAG_PRIORITY_CRITICAL);publishLocalService(PowerManagerInternal.class, mLocalService);Watchdog.getInstance().addMonitor(this);Watchdog.getInstance().addThread(mHandler);
}Override
public void onBootPhase(int phase) {if (phase PHASE_SYSTEM_SERVICES_READY) {systemReady();} else if (phase PHASE_THIRD_PARTY_APPS_CAN_START) {incrementBootCount();} else if (phase PHASE_BOOT_COMPLETED) {synchronized (mLock) {...}...
} 服务名称 作用 1 ArtModuleServiceInitializer 初始化 ART 模块服务管理器 2 Watchdog 系统守护线程监听系统服务是否发生死锁 3 platformCompat 平台兼容性服务为其他服务提供兼容性支持 4 FileIntegrityService 文件完整性服务响应应用和系统的完整性请求 5 Installer 安装器服务等待 Installd 启动完成 6 DeviceIdentifiersPolicyService 设备标识符策略服务注册在启动应用程序管理器之前 7 UriGrantsManagerService URI 授权管理服务 8 PowerStatsService 电源统计数据跟踪服务 9 MemtrackProxyService 内存跟踪代理服务早于 ActivityManagerService 启动 10 AccessCheckingService 访问检查服务提供新的权限和应用操作实现 11 ActivityManagerService 系统核心服务管理活动和任务 12 DataLoaderManagerService 数据加载器管理服务 13 IncrementalService 增量安装服务 14 PowerManagerService 电源管理服务 15 ThermalManagerService 热管理服务 16 HintManagerService 提示管理服务 17 RecoverySystemService 设备进入Recovery模式时提供各种功能和操作 18 LightsService LED 和显示背光管理服务 19 DisplayOffloadService 显示卸载服务 20 SidekickService SidekickService服务通常与其他应用程序一起工作为用户提供额外的功能和支持 21 DisplayManagerService 显示管理器服务 22 DomainVerificationService selinux权限验证服务 23 PackageManagerService 包管理器服务管理应用程序包和应用程序 24 DexUseManagerLocal 本地 Dex 使用管理器 25 OtaDexOptService A/B OTA dexopt 管理服务 26 UserManagerService 用户管理服务 27 OverlayManagerService 用于管理和处理窗口覆盖Overlay相关的操作 28 ResourcesManagerService 资源管理器服务 29 SensorPrivacyService 传感器隐私管理服务 30 SensorService 传感器服务
2.2 startCoreServices
启动系统核心服务如下 private void startCoreServices(NonNull TimingsTraceAndSlog t) {...mSystemServiceManager.startService(SystemConfigService.class);mSystemServiceManager.startService(BatteryService.class);mSystemServiceManager.startService(UsageStatsService.class);mActivityManagerService.setUsageStatsManager(LocalServices.getService(UsageStatsManagerInternal.class));mWebViewUpdateService mSystemServiceManager.startService(WebViewUpdateService.class);mSystemServiceManager.startService(CachedDeviceStateService.class);mSystemServiceManager.startService(BinderCallsStatsService.LifeCycle.class);mSystemServiceManager.startService(LooperStatsService.Lifecycle.class);mSystemServiceManager.startService(ROLLBACK_MANAGER_SERVICE_CLASS);mSystemServiceManager.startService(NativeTombstoneManagerService.class);mSystemServiceManager.startService(BugreportManagerService.class);mSystemServiceManager.startService(GpuService.class);mSystemServiceManager.startService(RemoteProvisioningService.class);mSystemServiceManager.startService(CpuMonitorService.class);} 服务名称 作用 1 SystemConfigService 用于管理和提供系统级别的配置信息。SystemConfigService服务为应用程序和系统组件提供了一种访问系统配置信息的方式 2 BatteryService 用于管理和提供电池相关的信息和功能。BatteryService服务为应用程序和系统组件提供了一种访问电池状态和控制电池使用的方式 3 WebViewUpdateService 用于管理和提供WebView组件的更新信息。WebView是Android系统中的一个内置组件用于在应用程序中显示和处理网页内容 4 CachedDeviceStateService 用于缓存和提供设备状态信息。这个服务会在设备启动时创建并在整个系统运行过程中提供设备状态信息 5 BinderCallsStatsService 为系统提供了一种收集和分析Binder通信性能数据的服务 6 LooperStatsService 为系统提供了一种收集和分析Looper线程性能数据的服务 7 RollbackManagerService 为系统提供了一种管理和实现系统回滚功能的方式以便在出现问题时快速恢复系统状态 8 NativeTombstoneManagerService 为系统提供了一种管理和收集Native堆栈Tombstone信息以便在进程发生native crash时快速定位问题 9 BugreportManagerService 为系统提供了一种管理和实现Bugreport信息以便在需要时快速收集系统和程序状态信息 10 GpuService 为系统提供了一种访问GPU信息和控制GPU使用的服务 11 RemoteProvisioningService 为系统提供了一种管理和实现远程设备配置功能以便在需要时远程配置设备 12 CpuMonitorService 用于管理和提供CPU相关的信息和功能
2.3 startOtherServices
启动系统其它的服务如下
private void startOtherServices(NonNull TimingsTraceAndSlog t) {...mSystemServiceManager.startService(DropBoxManagerService.class);mSystemServiceManager.startService(ALARM_MANAGER_SERVICE_CLASS);mSystemServiceManager.startService(CameraServiceProxy.class);WindowManagerService.main(context, inputManager, !mFirstBoot,pwm, mActivityManagerService.mActivityTaskManager);// 这类系统服务可以做裁剪 if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_PRINTING)) {t.traceBegin(StartPrintManager);mSystemServiceManager.startService(PRINT_MANAGER_SERVICE_CLASS);t.traceEnd();}}if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_COMPANION_DEVICE_SETUP)) {t.traceBegin(StartCompanionDeviceManager);mSystemServiceManager.startService(COMPANION_DEVICE_MANAGER_SERVICE_CLASS);t.traceEnd();// VirtualDeviceManager depends on CDM to control the associations.t.traceBegin(StartVirtualDeviceManager);mSystemServiceManager.startService(VIRTUAL_DEVICE_MANAGER_SERVICE_CLASS);t.traceEnd();}...// 这里会启动launcher进程mActivityManagerService.systemReady(() - { ...}...// 启动systemuistartSystemUi(context, windowManagerF);...
} 服务名称 作用 1 KeyChainSystemService 用于管理和提供密钥链KeyChain相关的信息和功能。密钥链是一种在Android系统中存储和管理敏感信息如密码、密钥等的机制通常用于实现设备安全、数据加密等场景。 2 DropBoxManagerService app进程发生ANR、native crash时收集相关debug信息 3 ContentService 为系统提供了一种管理和实现ContentProvider功能的方式以便在需要时实现数据共享和访问 4 AlarmManagerService 定时任务 5 InputManagerService 管理和提供输入设备相关的信息和功能 6 DeviceStateManagerService 用于管理设备的状态信息 7 WindowManagerService 负责管理设备上的窗口和界面。它为应用程序提供了一个统一的接口用于创建、显示、隐藏、移动、调整大小等操作窗口。 8 BluetoothService 理蓝牙设备的连接和通信。它提供了一系列API允许应用程序通过蓝牙进行数据交换、文件传输、音频流传输等操作。 9 StorageManagerService 负责管理设备的存储空间。它为应用程序提供了一个统一的接口用于访问设备的内部存储如闪存和外部存储如SD卡。 10 OemLockService 管理设备的OEM锁定状态 11 DeviceIdleController 管理设备的空闲状态。当设备处于空闲状态时DeviceIdleController可以自动执行一些节能措施如降低屏幕亮度、关闭无线网络等以延长设备的电池寿命。 12 DevicePolicyManagerService 管理设备的策略和安全设置。 13 StatusBarManagerService 管理设备的状态栏。它提供了一系列API允许应用程序在状态栏上显示通知、图标、进度条等信息。 14 NetworkManagementService 管理设备的网络连接。它提供了一系列API允许应用程序获取设备的网络状态、连接类型、IP地址等信息并可以控制设备的网络连接。 15 NetworkStatsService 统计设备的网络使用情况。它提供了一系列API允许应用程序获取设备的网络流量统计信息如总流量、各个应用程序的流量等。 16 NetworkPolicyManagerService 管理设备的网络策略。它提供了一系列API允许设备管理员对设备的网络连接进行策略管理如限制应用程序的网络访问、设置网络优先级等。 17 SystemUpdateManagerService 管理设备的系统更新。它提供了一系列API允许对设备的系统更新进行管理如检查系统更新、下载系统更新、安装系统更新等。 18 NotificationManagerService 管理设备的通知。它提供了一系列API允许应用程序在通知栏上显示通知如消息通知、提醒通知等。 19 DeviceStorageMonitorService 监控设备的存储空间。它提供了一系列API允许应用程序获取设备的存储空间信息如总容量、已用容量、可用容量等。 20 AudioService 管理设备的音频。允许应用程序控制设备的音频输出如播放音乐、播放铃声等。 21 BroadcastRadioService 管理设备的广播电台。允许应用程序接收广播电台的节目如新闻、音乐等。 22 AdbService 管理设备的ADB连接。允许开发人员通过ADB连接设备进行调试和测试。 23 UsbService 管理设备的USB连接。允许应用程序通过USB连接设备进行数据传输和通信 24 GestureLauncher 用于识别和响应用户的手势操作。允许应用程序检测和响应用户的手势操作如滑动、捏合、旋转等。 25 SensorNotificationService 管理设备的传感器通知。允许应用程序获取设备的传感器信息如加速度计、陀螺仪等 26 DiskStatsService 管理设备的磁盘状态。允许应用程序获取设备的磁盘状态信息如分区大小、使用情况等。 27 RuntimeService 管理设备的运行时环境。允许应用程序获取设备的运行时信息如内存使用情况、CPU使用情况等。 28 GraphicsStatsService 管理设备的图形性能 29 FaceSensorService 管理设备的面部识别功能 30 HealthService 用于管理设备的健康状态。允许应用程序获取设备的健康状态信息如电池电量、温度等。 31 SdkSandboxManagerService 管理设备的SDK沙盒环境。允许应用程序获取设备的SDK沙盒信息如应用程序的权限、资源等。 32 PermissionPolicyService 管理设备的权限策略 33 LockSettingsService 管理设备的锁定设置如屏幕锁定方式、密码等。 34 LauncherAppsService 管理设备的启动器应用程序。允许应用程序获取设备的启动器应用程序信息如启动器应用程序的名称、图标等。 35 AppServiceManager 管理设备的应用程序服务 36 GameManagerService 用于管理游戏的运行和状态 37 LocationManagerService 用于管理设备的位置信息允许应用程序获取设备的位置信息如经纬度、海拔等 38 FingerprintSensor 管理设备的指纹识别功能 39 IoTSystemService 理设备的物联网功能 40 SafetyCenterService 理设备的安全功能。允许应用程序获取设备的安全信息如病毒扫描、防火墙等 其它系统服务 KeyAttestationApplicationIdProviderService、BinaryTransparencyService、SchedulingPolicyService、TelecomLoaderService、TelephonyRegistry、EntropyMixer、AccountManagerService、InstallSystemProviders、 RoleManagerService、VibratorManagerService、DynamicSystemService、ConsumerIrService、ResourceEconomy、 CameraServiceProxy、VrManagerService、IpConnectivityMetrics、NetworkWatchlistService、PinnerService、 ProfcollectForwardingService、SignedConfigService、AppIntegrityService、LogcatManagerService、 InputMethodManagerService、AccessibilityManagerService、UiModeManagerService、LocaleManagerService、 GrammaticalInflectionService、AppHibernationService、LockSettingsService、PersistentDataBlockService、 MusicRecognitionManagerService、SpeechRecognitionManagerService、AppPredictionService、 ContentSuggestionsService、SearchUiService、SmartspaceService、FontManagerService、TextServicesManager、 TextClassificationManagerService、NetworkScoreService、RttService、WifiAwareService、WifiP2PService、 LowpanService、PacProxyService、ConnectivityService、MiCarNetService、VpnManagerService、VcnManagementService、UpdateLockService、TimeDetectorService、CountryDetectorService、 TimeZoneDetectorService、AltitudeService、LocationTimeZoneManagerService、GnssTimeUpdateService、 SearchManagerService、WallpaperManagerService、WallpaperEffectsGenerationService、SoundTriggerMiddlewareService、DockObserver、ThermalObserver、WiredAccessoryManagerService、 MidiManagerService、SerialService、HardwarePropertiesManagerService、TwilightService、ColorDisplayService、 SoundTriggerService、TrustManagerService、BackupManager、AppWidgetService、VoiceRecognitionManager、 ContextHubSystemService、NetworkTimeUpdateService、EmergencyAffordanceService、DreamManagerService、 CoverageService、PrintManager、AttestationVerificationService、CompanionDeviceManager、VirtualDeviceManager、RestrictionManager、MediaSessionService、HdmiControlService、TvInteractiveAppManager、TvInputManager、TunerResourceManager、MediaResourceMonitor、 TvRemoteService、MediaRouterService、IrisSensor、FingerprintSensor、BiometricService、 AuthService、DynamicCodeLoggingService、PruneInstantAppsJobService、ShortcutService、 CrossProfileAppsService、PeopleService、MediaMetricsManager、BackgroundInstallControlService、 MediaProjectionManager、WearPowerService、WearConnectivityService、WearDisplayService、 WearTimeService、WearGlobalActionsService、SliceManagerService、 StatsCompanion、StatsPullAtomService、BootstrapAtomService、IncidentCompanionService、 AdServicesManagerService、OnDevicePersonalizationSystemService、MmsService、AutoFillService、 CredentialManagerService、TranslationManagerService、SelectionToolbarManagerService、ClipboardService、 TracingServiceProxy、DeviceSpecificServices、MediaCommunicationService、 AppCompatOverridesService、HealthConnectManagerService等
2.4 startApexServices
启动系统apex服务如下
private void startApexServices(NonNull TimingsTraceAndSlog t) {ListApexSystemServiceInfo services ApexManager.getInstance().getApexSystemServices();for (ApexSystemServiceInfo info : services) {String name info.getName();String jarPath info.getJarPath();t.traceBegin(starting name);if (TextUtils.isEmpty(jarPath)) {mSystemServiceManager.startService(name);} else {mSystemServiceManager.startServiceFromJar(name, jarPath);}t.traceEnd();}}
三、如何使用系统服务
3.1 app进程调用系统服务
以PMS服务为例app进程通过获取PMS服务代理---PowerManager对象调用PowerManager中的接口
// 获取PowerManager实例
PowerManager powerManager (PowerManager) getSystemService(Context.POWER_SERVICE);
// 调用PowerManager类中的接口
PowerManager.WakeLock wakeLock powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, MyWakeLockTag);3.2 native进程调用系统服务
通过binder对parcel数据通信
#include binder/IServiceManager.h
#include binder/Parcel.hspIServiceManager sm defaultServiceManager();
spIBinder binder sm-getService(String16(power));
if (!binder) {return EXIT_FAILURE;
}
Parcel data, result;
data.writeInterfaceToken(String16(android.os.IPowerManager));
char d[] {0x00};
data.write(d, sizeof(d));
// 6表示对应的方法ID
binder-transact(6, data, result);
或者直接调用binder接口
#include binder/IActivityManager.h
#include binder/IBinder.h
#include binder/IServiceManager.hint openContentProviderFile(const String16 uri)
{int fd -1;spIServiceManager sm defaultServiceManager();spIBinder binder sm-getService(String16(activity));spIActivityManager am interface_castIActivityManager(binder);if (am ! NULL) {fd am-openContentUri(uri);}return fd;
}
3.3 system_server进程中两个服务之间的调用
system_server进程中的服务间调用属于进程内部通信。如PMS服务启动时会将内部的mLocalService对象注册到本地service管理中对外提供一个PowerManagerInternal类及接口给其它服务调用如下
// 其它服务中通过获取PowerManagerInternal对象调用接口
private PackageManagerInternal mPackageManagerInternal;mLocalPowerManager getLocalService(PowerManagerInternal.class);
mLocalPowerManager.getLowPowerState(ServiceType.QUICK_DOZE).batterySaverEnabled);// frameworks/base/core/java/android/os/PowerManagerInternal.java
// 抽象方法在具体实现类中实现
public abstract PowerSaveState getLowPowerState(int serviceType);// frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java
public final class PowerManagerService extends SystemServiceimplements Watchdog.Monitor {...Overridepublic void onStart() {// 注册到servicemanager中用于进程间通信publishBinderService(Context.POWER_SERVICE, mBinderService, /* allowIsolated */ false,DUMP_FLAG_PRIORITY_DEFAULT | DUMP_FLAG_PRIORITY_CRITICAL);// 加入到本地service中用于进程内部调用 publishLocalService(PowerManagerInternal.class, mLocalService);...}// 内部类继承PowerManagerInternal并实现父类抽象方法final class LocalService extends PowerManagerInternal {...Overridepublic PowerSaveState getLowPowerState(ServiceType int serviceType) {return mBatterySaverPolicy.getBatterySaverPolicy(serviceType);}...}...
}
四、如何添加一个系统服务
添加步骤
1准备系统服务代码DemoSystemService.java和Android.bp文件
// 继承SystemService实现Watchdog.Monitor接口
public final class DemoManagerService extends SystemServiceimplements Watchdog.Monitor {// 服务名称为 demoString SERVICE_NAME demo;...// 重写onStart和onBootPhase方法Overridepublic void onStart() {// 发布服务publishBinderService(SERVICE_NAME, mBinderService, /* allowIsolated */ false,DUMP_FLAG_PRIORITY_DEFAULT | DUMP_FLAG_PRIORITY_CRITICAL);// 用于监控DemoManagerService是否发生死锁Watchdog.getInstance().addMonitor(this);Watchdog.getInstance().addThread(mHandler);}Overridepublic void onBootPhase(int phase) {...}...
}
filegroup {name: demo--system-service-sources,srcs: [DemoSystemService.java],
}
2将services.jar模块编译依赖新增模块
修改frameworks/base/services/Android.bp如下
java_library {name: services,...srcs: [:services-main-sources,:demo--system-service-sources],...
}
3SystemServer.java中启动Demo服务
修改frameworks/base/services/java/com/android/server/SystemServer.java, 启动DemoSystemService如下
public final class SystemServer implements Dumpable {...private void startOtherServices(NonNull TimingsTraceAndSlog t) {t.traceBegin(StartDemoSystemService);mSystemServiceManager.startService(DemoSystemService.class);t.traceEnd();}...
}
4添加selinux规则
修改system/sepolicy库添加demo服务的标签和规则注意添加的服务名称为demo如下
// system/sepolicy/private/compat/32.0/32.0.ignore.cil
vendor_vm_file
virtual_device_service
wallpaper_effects_generation_service
demo_service// system/sepolicy/prebuilts/api/32.0/private/service_contexts
demo u:object_r:demo_service:s0// system/sepolicy/prebuilts/api/32.0/public/service.te
type demo_service, system_server_service, service_manager_type;
五、如何裁剪系统服务
所谓的系统服务裁剪就是不让服务启动且其它获取该服务的地方有判空避免运行时空指针报错。以printmanagerservice服务为例
// packagemanager
public static final String FEATURE_PRINTING android.software.print;private void startOtherServices(NonNull TimingsTraceAndSlog t) {// 这类系统服务可以做裁剪只需让hasSystemFeature方法返回false if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_PRINTING)) {t.traceBegin(StartPrintManager);mSystemServiceManager.startService(PRINT_MANAGER_SERVICE_CLASS);t.traceEnd();}}...
}
hasSystemFeature实现
// 通过mAvailableFeatures得到所有的feature
public boolean hasSystemFeature(String name, int version) {// allow instant applicationssynchronized (mAvailableFeatures) {final FeatureInfo feat mAvailableFeatures.get(name);if (feat null) {return false;} else {return feat.version version;}}
}// 该方法维护mAvailableFeatures列表
private void addFeature(String name, int version) {FeatureInfo fi mAvailableFeatures.get(name);if (fi null) {fi new FeatureInfo();fi.name name;fi.version version;mAvailableFeatures.put(name, fi);} else {fi.version Math.max(fi.version, version);}
}
// 系统启动时会去读取handheld_core_hardware.xml配置文件存到mAvailableFeatures列表
SystemConfig() {TimingsTraceLog log new TimingsTraceLog(TAG, Trace.TRACE_TAG_SYSTEM_SERVER);log.traceBegin(readAllPermissions);try {readAllPermissions();readPublicNativeLibrariesList();} finally {log.traceEnd();}
}// 读取handheld_core_hardware.xml配置文件
private void readPermissionsFromXml(final XmlPullParser parser, File permFile,int permissionFlag) {...case feature: {if (allowFeatures) {String fname parser.getAttributeValue(null, name);int fversion XmlUtils.readIntAttribute(parser, version, 0);boolean allowed;if (!lowRam) {allowed true;} else {String notLowRam parser.getAttributeValue(null, notLowRam);allowed !true.equals(notLowRam);}if (fname null) {Slog.w(TAG, name without name in permFile at parser.getPositionDescription());} else if (allowed) {addFeature(fname, fversion);}} else {logNotAllowedInPartition(name, permFile, parser);}XmlUtils.skipCurrentTag(parser);} break;...
}
只要注释掉feature nameandroid.software.print /hasSystemFeature方法返回falseprintmanagerservice服务就不会启动如下
// frameworks/native/data/etc/handheld_core_hardware.xml!-- basic system services --feature nameandroid.software.app_widgets /feature nameandroid.software.telecom /feature nameandroid.software.voice_recognizers notLowRamtrue /feature nameandroid.software.backup /feature nameandroid.software.home_screen /feature nameandroid.software.input_methods /feature nameandroid.software.picture_in_picture notLowRamtrue /feature nameandroid.software.activities_on_secondary_displays notLowRamtrue /// feature nameandroid.software.print /feature nameandroid.software.companion_device_setup /feature nameandroid.software.autofill /feature nameandroid.software.credentials /feature nameandroid.software.cant_save_state /feature nameandroid.software.secure_lock_screen /feature nameandroid.software.window_magnification /...
/permissions
PRODUCT_COPY_FILES : \ frameworks/native/data/etc/handheld_core_hardware.xml:system/etc/permissions/handheld_core_hardware.xml
app进程或系统其它服务在使用该服务前会做空判断避免服务获取不到引入的空指针错误
// 服务注册
registerService(Context.PRINT_SERVICE, PrintManager.class,new CachedServiceFetcherPrintManager() {Overridepublic PrintManager createService(ContextImpl ctx) throws ServiceNotFoundException {IPrintManager service null;// If the feature not present, dont try to look up every timeif (ctx.getPackageManager().hasSystemFeature(PackageManager.FEATURE_PRINTING)) {service IPrintManager.Stub.asInterface(ServiceManager.getServiceOrThrow(Context.PRINT_SERVICE));}final int userId ctx.getUserId();final int appId UserHandle.getAppId(ctx.getApplicationInfo().uid);return new PrintManager(ctx.getOuterContext(), service, userId, appId);
}});public PrintManager(Context context, IPrintManager service, int userId, int appId) {mContext context;mService service;...
}// app进程调用服务相关接口之前会做null判断避免服务获取失败导致空指针错误
public PrintJob getPrintJob(PrintJobId printJobId) {if (mService null) {Log.w(LOG_TAG, Feature android.software.print not available);return null;}try {PrintJobInfo printJob mService.getPrintJobInfo(printJobId, mAppId, mUserId);if (printJob ! null) {return new PrintJob(printJob, this);}} catch (RemoteException re) {throw re.rethrowFromSystemServer();}return null;
}// 其它服务在调用该服务之前会做hasSystemFeature判断是否可用
Override
public int getAvailabilityStatus() {return mPackageManager.hasSystemFeature(PackageManager.FEATURE_PRINTING) mPrintManager ! null? AVAILABLE : UNSUPPORTED_ON_DEVICE;
}
六、其它模块
6.1 NativeCrashListener
NativeCrashListener线程模块用于监听native crash事件即当某个进程发生native crash时由crash_dump64进程通过socket(ndebugsocket)方式将crash debug信息传给NativeCrashListener模块并传给AMS服务写入dropbox. 流程框架 system_server进程启动的systemReady阶段创建NativeCrashListener线程该线程创建ndebugsocket socket服务端当有进程发生native crash时crash_dump64客户端进程通过socket与system_server通信最后将数据存到data/system/dropbox目录。 核心代码段 // frameworks/base/services/java/com/android/server/SystemServer.javamActivityManagerService.systemReady(() - {...mSystemServiceManager.startBootPhase(t, SystemService.PHASE_ACTIVITY_MANAGER_READY);...mActivityManagerService.startObservingNativeCrashes();...
}
// rameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void startObservingNativeCrashes() {final NativeCrashListener ncl new NativeCrashListener(this);ncl.start();
}
// frameworks/base/services/core/java/com/android/server/am/NativeCrashListener.javafinal class NativeCrashListener extends Thread {static final String DEBUGGERD_SOCKET_PATH /data/system/ndebugsocket;static final long SOCKET_TIMEOUT_MILLIS 10000; final ActivityManagerService mAm;// 内部类线程class NativeCrashReporter extends Thread {ProcessRecord mApp;int mSignal;boolean mGwpAsanRecoverableCrash;String mCrashReport;NativeCrashReporter(ProcessRecord app, int signal, boolean gwpAsanRecoverableCrash,String report) {super(NativeCrashReport);mApp app;mSignal signal;mGwpAsanRecoverableCrash gwpAsanRecoverableCrash;mCrashReport report;}Overridepublic void run() {try {CrashInfo ci new CrashInfo();ci.exceptionClassName Native crash;ci.exceptionMessage Os.strsignal(mSignal);ci.throwFileName unknown;ci.throwClassName unknown;ci.throwMethodName unknown;ci.stackTrace mCrashReport;// crash数据传给AMS由AMS写入dropboxmAm.handleApplicationCrashInner(mGwpAsanRecoverableCrash ? native_recoverable_crash : native_crash,mApp, mApp.processName, ci);if (DEBUG) Slog.v(TAG, -- handleApplicationCrash() returned);} catch (Exception e) {Slog.e(TAG, Unable to report native crash, e);}}}// 在system_server进程启动的systemReady阶段执行创建socke server进入循环监听Overridepublic void run() {final byte[] ackSignal new byte[1];{File socketFile new File(DEBUGGERD_SOCKET_PATH);if (socketFile.exists()) {socketFile.delete();}}try {FileDescriptor serverFd Os.socket(AF_UNIX, SOCK_STREAM, 0);final UnixSocketAddress sockAddr UnixSocketAddress.createFileSystem(DEBUGGERD_SOCKET_PATH);Os.bind(serverFd, sockAddr);Os.listen(serverFd, 1);Os.chmod(DEBUGGERD_SOCKET_PATH, 0777);while (true) {FileDescriptor peerFd null;try {if (MORE_DEBUG) Slog.v(TAG, Waiting for debuggerd connection);peerFd Os.accept(serverFd, null /* peerAddress */);if (MORE_DEBUG) Slog.v(TAG, Got debuggerd socket peerFd);if (peerFd ! null) {// 数据客户端的信息consumeNativeCrashData(peerFd);}} catch (Exception e) {Slog.w(TAG, Error handling connection, e);} finally {...}}// 读取client socket数据存到byte[] bufferstatic int readExactly(FileDescriptor fd, byte[] buffer, int offset, int numBytes)throws ErrnoException, InterruptedIOException {int totalRead 0;while (numBytes 0) {int n Os.read(fd, buffer, offset totalRead, numBytes);if (n 0) {if (DEBUG) {Slog.w(TAG, Needed numBytes but saw n);}return -1; // premature EOF or timeout}numBytes - n;totalRead n;}return totalRead;}// Read a crash report from the connectionvoid consumeNativeCrashData(FileDescriptor fd) {final byte[] buf new byte[4096];final ByteArrayOutputStream os new ByteArrayOutputStream(4096);try {StructTimeval timeout StructTimeval.fromMillis(SOCKET_TIMEOUT_MILLIS);Os.setsockoptTimeval(fd, SOL_SOCKET, SO_RCVTIMEO, timeout);Os.setsockoptTimeval(fd, SOL_SOCKET, SO_SNDTIMEO, timeout);int headerBytes readExactly(fd, buf, 0, 9);boolean gwpAsanRecoverableCrash buf[8] ! 0;...// byte[]转Stringint bytes;do {// get some databytes Os.read(fd, buf, 0, buf.length);if (bytes 0) {if (MORE_DEBUG) {String s new String(buf, 0, bytes, UTF-8);Slog.v(TAG, READ bytes s);}// did we just get the EOD null byte?if (buf[bytes - 1] 0) {os.write(buf, 0, bytes - 1); // exclude the EOD tokenbreak;}// no EOD, so collect it and read moreos.write(buf, 0, bytes);}} while (bytes 0);if (!gwpAsanRecoverableCrash) {synchronized (mAm) {synchronized (mAm.mProcLock) {pr.mErrorState.setCrashing(true);pr.mErrorState.setForceCrashReport(true);}}}final String reportString new String(os.toByteArray(), UTF-8);(new NativeCrashReporter(pr, signal, gwpAsanRecoverableCrash, reportString)).start();} catch (Exception e) {Slog.e(TAG, Exception dealing with report, e);// ugh, fail.}}}6.2 Android watchdog
Android watchdog用于监测系统服务、UI线程、动画线程等是否出现死锁或卡死system_server进程启动时会启动watchdog线程进入监听系统服务启动时会加入watchdog监听。
private void startBootstrapServices(NonNull TimingsTraceAndSlog t) {......// Start the watchdog as early as possible so we can crash the system server// if we deadlock during early boott.traceBegin(StartWatchdog);final Watchdog watchdog Watchdog.getInstance(); // 对象创建watchdog.start(); // 启动watchdong线程mDumper.addDumpable(watchdog);......
}实现原理
以PMS服务为例
1PMS服务实现Watchdog.Monitor接口服务启动时将PMS服务对象加入到watchdong的Monitor列表
2system_server进程启动时会启动watchdog线程每隔30s会启动monitor线程调用monitor列表中的PMS对象加锁的monitor方法如果超过30s没有返回说明一直在等待锁即PMS服务卡死。
// PowerManagerService.java
public final class PowerManagerService extends SystemServiceimplements Watchdog.Monitor {...Overridepublic void onStart() {// 加入watchdog监听Watchdog.getInstance().addMonitor(this); // pms服务实现了Watchdog.Monitor接口...}// 在watch dog中调用超过30s没有返回说明一直在等待锁即服务卡死Override public void monitor() {// Grab and release lock for watchdog monitor to detect deadlocks.synchronized (mLock) {}}...
}// frameworks/base/services/core/java/com/android/server/Watchdog.java
public class Watchdog implements Dumpable {...private final Thread mThread;private final HandlerChecker mMonitorChecker;private Watchdog() {// 创建watchdog线程mThread new Thread(this::run, watchdog);// 创建monitor线程mMonitorChecker new HandlerChecker(new Handler(t.getLooper()), monitor thread);...}public void start() {// 启动watchdog线程执行Watchdog类中的run方法mThread.start();}public void addMonitor(Monitor monitor) {synchronized (mLock) {mMonitorChecker.addMonitorLocked(monitor);}}private void run() {boolean waitedHalf false;while (true) {ListHandlerChecker blockedCheckers Collections.emptyList();String subject ;boolean allowRestart true;int debuggerWasConnected 0;boolean doWaitedHalfDump false;final long watchdogTimeoutMillis mWatchdogTimeoutMillis;final long checkIntervalMillis watchdogTimeoutMillis / 2;final ArrayListInteger pids;synchronized (mLock) {long timeout checkIntervalMillis;for (int i0; imHandlerCheckers.size(); i) {HandlerCheckerAndTimeout hc mHandlerCheckers.get(i);// 执行内部类HandlerChecker中的scheduleCheckLocked方法hc.checker().scheduleCheckLocked(hc.customTimeoutMillis().orElse(watchdogTimeoutMillis * Build.HW_TIMEOUT_MULTIPLIER));}...} public final class HandlerChecker implements Runnable {...private Monitor mCurrentMonitor;private final ArrayListMonitor mMonitors new ArrayListMonitor();private final ArrayListMonitor mMonitorQueue new ArrayListMonitor();HandlerChecker(Handler handler, String name) {mHandler handler;mName name;mCompleted true;}void addMonitorLocked(Monitor monitor) {mMonitorQueue.add(monitor);}public void scheduleCheckLocked(long handlerCheckerTimeoutMillis) {mWaitMaxMillis handlerCheckerTimeoutMillis;if (mCompleted) {// Safe to update monitors in queue, Handler is not in the middle of workmMonitors.addAll(mMonitorQueue);mMonitorQueue.clear();}if ((mMonitors.size() 0 mHandler.getLooper().getQueue().isPolling())|| (mPauseCount 0)) {mCompleted true;return;}if (!mCompleted) {// we already have a check in flight, so no needreturn;}mCompleted false;mCurrentMonitor null;mStartTimeMillis SystemClock.uptimeMillis();// 发送消息插入消息队列最开头执行下面的run()方法mHandler.postAtFrontOfQueue(this);}Overridepublic void run() {final int size mMonitors.size();for (int i 0 ; i size ; i) {synchronized (mLock) {mCurrentMonitor mMonitors.get(i);}// 开始监测服务是否出现死锁或卡死mCurrentMonitor.monitor();}synchronized (mLock) {mCompleted true;mCurrentMonitor null;}}...} // HandlerChecker内部类...
} // Watchdog
