网站seo搜索引擎优化教程,网站设计分工,vue做网站前端,免费模板网站下载文章目录 知识回顾启动第一个流程initZygote的流程 前言源码分析1.system_server2.SystemServer.main3,startBootstrapServices4,startService 拓展知识LoadApkcontext 对于Android context 大家是怎么理解的#xff1f;LocalServices.java: addServece方法中 ArrayMap和HashM… 文章目录 知识回顾启动第一个流程initZygote的流程 前言源码分析1.system_server2.SystemServer.main3,startBootstrapServices4,startService 拓展知识LoadApkcontext 对于Android context 大家是怎么理解的LocalServices.java: addServece方法中 ArrayMap和HashMap的区别AMS、PMS是谁启动的他们都是独立的进程吗WatchDog 看门狗机制简述system_server的启动 总结 知识回顾
启动第一个流程init
1挂载文件系统创建文件目录 调用selinux_setup权限安全相关 2初始化内存空间 初始化属性服务 创建Epoll 注册监听子进程重启异常操作等对子进程进行线程守护 3startPropertyServic 开启属性服务 进行监听 4LoadBootScripts 加载init.rc文件 进行解析 调用do_class_start 文件开启service 5Service::Start函数-fork子进程-并且执行app_process文件开启了zygote
Zygote的流程
1startVm函数注册jvm startReg函数注册jni环境唤起 Zygote.main 2,forkSystemServer 3,preload预加载class 系统资源 4调用runSelectLoop函数循环等待客户端连接 5有客户端的连接后调用processOneCommand()函数 fork进程初始化进程创建ProcessState初始化binder 6根据请求的targetClass 执行Main函数
前言
Android系统在启动的时候有两个非常重要的进程Zygote system_server。SystemServer是系统用来启动service的入口比如我们常用的 AMSWMSPMS等都是由它创建的。 SystemServer主要是创建SystemServiceManager对系统服务进行创建、启动以及管理。 源码分析
1.system_server
Zygote启动之后会调用ZygoteInit.java的main函数会执行forkSystemServer private static Runnable forkSystemServer(String abiList, String socketName,ZygoteServer zygoteServer) {……………………/* Hardcoded command line to start the system server *///准备 开启system_server的参数String args[] {--setuid1000,--setgid1000,--setgroups1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1023, 1024,1032,1065,3001,3002,3003,3006,3007,3009,3010,--capabilities capabilities , capabilities,--nice-namesystem_server,--runtime-args,--target-sdk-version VMRuntime.SDK_VERSION_CUR_DEVELOPMENT,com.android.server.SystemServer,};ZygoteArguments parsedArgs null;int pid;try {//把参数包装成ZygoteArgumentsparsedArgs new ZygoteArguments(args);Zygote.applyDebuggerSystemProperty(parsedArgs);Zygote.applyInvokeWithSystemProperty(parsedArgs);boolean profileSystemServer SystemProperties.getBoolean(dalvik.vm.profilesystemserver, false);if (profileSystemServer) {parsedArgs.mRuntimeFlags | Zygote.PROFILE_SYSTEM_SERVER;}/* Request to fork the system server process */
// fork出来system_server 还是调用到native层com_android_internal_os_Zygote_nativeForkSystemServerpid Zygote.forkSystemServer(parsedArgs.mUid, parsedArgs.mGid,parsedArgs.mGids,parsedArgs.mRuntimeFlags,null,parsedArgs.mPermittedCapabilities,parsedArgs.mEffectiveCapabilities);} catch (IllegalArgumentException ex) {throw new RuntimeException(ex);}/* For child process */if (pid 0) {if (hasSecondZygote(abiList)) {waitForSecondaryZygote(socketName);}//关闭掉ServerSocketzygoteServer.closeServerSocket();
//这里我们看到返回的是一个Runnable 就可以联想到Zygote中的MethodAndArgsCallerreturn handleSystemServerProcess(parsedArgs);}return null;}
//fork最终会调用到Native层
//com_android_internal_os_Zygote_nativeForkSystemServer
//。文件目录/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) {std::vectorint fds_to_close(MakeUsapPipeReadFDVector()),fds_to_ignore(fds_to_close);fds_to_close.push_back(gUsapPoolSocketFD);if (gUsapPoolEventFD ! -1) {fds_to_close.push_back(gUsapPoolEventFD);fds_to_ignore.push_back(gUsapPoolEventFD);}//调用forkCommon函数这个之前在Zygote中有跟踪过这里就不跟了。调用fork并返回pid_tpid_t pid ForkCommon(env, true,fds_to_close,fds_to_ignore);if (pid 0) {SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,permitted_capabilities, effective_capabilities,MOUNT_EXTERNAL_DEFAULT, nullptr, nullptr, true,false, nullptr, nullptr);} else if (pid 0) {ALOGI(System server process %d has been created, pid);gSystemServerPid pid;int status;if (waitpid(pid, status, WNOHANG) pid) {//做一次安全检查ALOGE(System server process %d has died. Restarting Zygote!, pid);RuntimeAbort(env, __LINE__, System server process has died. Restarting Zygote!);}if (UsePerAppMemcg()) {if (!SetTaskProfiles(pid, std::vectorstd::string{SystemMemoryProcess})) {ALOGE(couldnt add process %d into system memcg group, pid);}}}return pid;
}
private static Runnable handleSystemServerProcess(ZygoteArguments parsedArgs) {Os.umask(S_IRWXG | S_IRWXO);if (parsedArgs.mNiceName ! null) {Process.setArgV0(parsedArgs.mNiceName);}final String systemServerClasspath Os.getenv(SYSTEMSERVERCLASSPATH);if (systemServerClasspath ! null) {if (performSystemServerDexOpt(systemServerClasspath)) {sCachedSystemServerClassLoader null;}boolean profileSystemServer SystemProperties.getBoolean(dalvik.vm.profilesystemserver, false);if (profileSystemServer (Build.IS_USERDEBUG || Build.IS_ENG)) {try {prepareSystemServerProfile(systemServerClasspath);} catch (Exception e) {Log.wtf(TAG, Failed to set up system server profile, e);}}}if (parsedArgs.mInvokeWith ! null) {//这里是NullString[] args parsedArgs.mRemainingArgs;if (systemServerClasspath ! null) {String[] amendedArgs new String[args.length 2];amendedArgs[0] -cp;amendedArgs[1] systemServerClasspath;System.arraycopy(args, 0, amendedArgs, 2, args.length);args amendedArgs;}WrapperInit.execApplication(parsedArgs.mInvokeWith,parsedArgs.mNiceName, parsedArgs.mTargetSdkVersion,VMRuntime.getCurrentInstructionSet(), null, args);throw new IllegalStateException(Unexpected return from WrapperInit.execApplication);} else {createSystemServerClassLoader();//创建SystemServer的ClassLoaderClassLoader cl sCachedSystemServerClassLoader;//将创建好的ClassLoader赋值给clif (cl ! null) {Thread.currentThread().setContextClassLoader(cl);}//调用ZygoteInit.zygoteInit 和Zygote一样 创建ProcessState 打开binder 并调用RuntimeInit.applicationInit 返回startClass的Main函数的caller也 也就是执行com.android.server.SystemServer的main函数return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion,parsedArgs.mRemainingArgs, cl);}}
2.SystemServer.main
main函数转头就掉了run函数run函数中 创建了Looper、加载了android_server函数库、创建了SystemServiceManager(对服务进行创建、启动和管理)并且添加到LocalService一个ArrayMap中、startBootstrapServices(开启引导服务)、startCoreServices(开启核心服务)、startOtherServices(开启其他服务)、Looper开启。
public static void main(String[] args) {//转头就钓了run函数new SystemServer().run();
}private void run() {try {traceBeginAndSlog(InitBeforeStartServices);SystemProperties.set(SYSPROP_START_COUNT, String.valueOf(mStartCount));SystemProperties.set(SYSPROP_START_ELAPSED, String.valueOf(mRuntimeStartElapsedTime));SystemProperties.set(SYSPROP_START_UPTIME, String.valueOf(mRuntimeStartUptime));EventLog.writeEvent(EventLogTags.SYSTEM_SERVER_START,mStartCount, mRuntimeStartUptime, mRuntimeStartElapsedTime);if (System.currentTimeMillis() EARLIEST_SUPPORTED_TIME) {Slog.w(TAG, System clock is before 1970; setting to 1970.);SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);}String timezoneProperty SystemProperties.get(persist.sys.timezone);if (timezoneProperty null || timezoneProperty.isEmpty()) {Slog.w(TAG, Timezone not set; setting to GMT.);SystemProperties.set(persist.sys.timezone, GMT);}if (!SystemProperties.get(persist.sys.language).isEmpty()) {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, );}Binder.setWarnOnBlocking(true);PackageItemInfo.forceSafeLabels();SQLiteGlobal.sDefaultSyncMode SQLiteGlobal.SYNC_MODE_FULL;SQLiteCompatibilityWalFlags.init(null);Slog.i(TAG, Entered the Android system server!);int uptimeMillis (int) SystemClock.elapsedRealtime();EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, uptimeMillis);if (!mRuntimeRestart) {MetricsLogger.histogram(null, boot_system_server_init, uptimeMillis);}SystemProperties.set(persist.sys.dalvik.vm.lib.2, VMRuntime.getRuntime().vmLibrary());VMRuntime.getRuntime().clearGrowthLimit();VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);Build.ensureFingerprintProperty();Environment.setUserRequired(true);BaseBundle.setShouldDefuse(true);Parcel.setStackTraceParceling(true);BinderInternal.disableBackgroundScheduling(true);BinderInternal.setMaxThreads(sMaxBinderThreads);android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_FOREGROUND);android.os.Process.setCanSelfBackground(false);Looper.prepareMainLooper();//创建消息的LooperLooper.getMainLooper().setSlowLogThresholdMs(SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);//加载函数库 libandroid_servers.soSystem.loadLibrary(android_servers);if (Build.IS_DEBUGGABLE) {initZygoteChildHeapProfiling();}performPendingShutdown();// Initialize the system context.createSystemContext();//创建系统Context// Create the system service manager. 创建ServiceManagermSystemServiceManager new SystemServiceManager(mSystemContext);mSystemServiceManager.setStartInfo(mRuntimeRestart,mRuntimeStartElapsedTime, mRuntimeStartUptime);//将SystemServiceManager添加到LocalServices中 LocalService 内部其实就是一个ArrayMapLocalServices.addService(SystemServiceManager.class, mSystemServiceManager);// Prepare the thread pool for init tasks that can be parallelizedSystemServerInitThreadPool.get();} finally {traceEnd(); // InitBeforeStartServices}// Start services. 开启服务try {traceBeginAndSlog(StartServices);startBootstrapServices();//开启引导服务startCoreServices();//开启核心服务startOtherServices();//开启其他服务SystemServerInitThreadPool.shutdown();} catch (Throwable ex) {Slog.e(System, ******************************************);Slog.e(System, ************ Failure starting system services, ex);throw ex;} finally {traceEnd();}StrictMode.initVmDefaults(null);if (!mRuntimeRestart !isFirstBootOrUpgrade()) {int uptimeMillis (int) SystemClock.elapsedRealtime();MetricsLogger.histogram(null, boot_system_server_ready, uptimeMillis);final int MAX_UPTIME_MILLIS 60 * 1000;if (uptimeMillis MAX_UPTIME_MILLIS) {Slog.wtf(SYSTEM_SERVER_TIMING_TAG,SystemServer init took too long. uptimeMillis uptimeMillis);}}if (!VMRuntime.hasBootImageSpaces()) {Slog.wtf(TAG, Runtime is not running with a boot image!);}// Loop forever.//loop启动Looper.loop();throw new RuntimeException(Main thread loop unexpectedly exited);
}
3,startBootstrapServices
开启了看门狗(用于监控system_server一旦出现问题会杀死SystemServerSystemServer撕掉会告诉Zygote Zygote接收到之后会杀死自己 然后告诉init init又会重启Zygote并且激活对应的onRestart)以及相当多的服务其中有我们熟悉的Installer、ActivityTaskManagerService、ActivityManagerService、PowerManagerService、PackageManagerService等等基本上就是通过startService方法
private void startBootstrapServices() {traceBeginAndSlog(StartWatchdog);final Watchdog watchdog Watchdog.getInstance();watchdog.start();//开启看门狗traceEnd();Slog.i(TAG, Reading configuration...);final String TAG_SYSTEM_CONFIG ReadingSystemConfig;traceBeginAndSlog(TAG_SYSTEM_CONFIG);SystemServerInitThreadPool.get().submit(SystemConfig::getInstance, TAG_SYSTEM_CONFIG);traceEnd();traceBeginAndSlog(StartInstaller);//开启Installer服务Installer installer mSystemServiceManager.startService(Installer.class);traceEnd();traceBeginAndSlog(DeviceIdentifiersPolicyService);//开启设备标识符访问策略服务mSystemServiceManager.startService(DeviceIdentifiersPolicyService.class);traceEnd();traceBeginAndSlog(UriGrantsManagerService);mSystemServiceManager.startService(UriGrantsManagerService.Lifecycle.class);traceEnd();// Activity manager runs the show.traceBeginAndSlog(StartActivityManager);//启动ActivityTaskManagerService、mActivityManagerService服务并关联systemServiceManager以及installerActivityTaskManagerService atm mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();mActivityManagerService ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);mActivityManagerService.setSystemServiceManager(mSystemServiceManager);mActivityManagerService.setInstaller(installer);mWindowManagerGlobalLock atm.getGlobalLock();traceEnd();// Power manager needs to be started early because other services need it.// Native daemons may be watching for it to be registered so it must be ready// to handle incoming binder calls immediately (including being able to verify// the permissions for those calls).traceBeginAndSlog(StartPowerManager);//开启PowerManagerService服务mPowerManagerService mSystemServiceManager.startService(PowerManagerService.class);traceEnd();traceBeginAndSlog(StartThermalManager);mSystemServiceManager.startService(ThermalManagerService.class);traceEnd();// Now that the power manager has been started, let the activity manager// initialize power management features.traceBeginAndSlog(InitPowerManagement);mActivityManagerService.initPowerManagement();traceEnd();// Bring up recovery system in case a rescue party needs a reboottraceBeginAndSlog(StartRecoverySystemService);mSystemServiceManager.startService(RecoverySystemService.class);traceEnd();// Now that we have the bare essentials of the OS up and running, take// note that we just booted, which might send out a rescue party if// were stuck in a runtime restart loop.RescueParty.noteBoot(mSystemContext);// Manages LEDs and display backlight so we need it to bring up the display.traceBeginAndSlog(StartLightsService);mSystemServiceManager.startService(LightsService.class);traceEnd();traceBeginAndSlog(StartSidekickService);// Package manager isnt started yet; need to use SysProp not hardware featureif (SystemProperties.getBoolean(config.enable_sidekick_graphics, false)) {mSystemServiceManager.startService(WEAR_SIDEKICK_SERVICE_CLASS);}traceEnd();// Display manager is needed to provide display metrics before package manager// starts up.traceBeginAndSlog(StartDisplayManager);mDisplayManagerService mSystemServiceManager.startService(DisplayManagerService.class);traceEnd();// We need the default display before we can initialize the package manager.traceBeginAndSlog(WaitForDisplay);mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);traceEnd();// Only run core apps if were encrypting the device.String cryptState VoldProperties.decrypt().orElse();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());}traceBeginAndSlog(StartPackageManagerService);try {Watchdog.getInstance().pauseWatchingCurrentThread(packagemanagermain);//创建PackageManagerService服务mPackageManagerService PackageManagerService.main(mSystemContext, installer,mFactoryTestMode ! FactoryTest.FACTORY_TEST_OFF, mOnlyCore);} finally {Watchdog.getInstance().resumeWatchingCurrentThread(packagemanagermain);}mFirstBoot mPackageManagerService.isFirstBoot();mPackageManager mSystemContext.getPackageManager();traceEnd();if (!mRuntimeRestart !isFirstBootOrUpgrade()) {MetricsLogger.histogram(null, boot_package_manager_init_ready,(int) SystemClock.elapsedRealtime());}// Manages A/B OTA dexopting. This is a bootstrap service as we need it to rename// A/B artifacts after boot, before anything else might touch/need them.// Note: this isnt needed during decryption (we dont have /data anyways).if (!mOnlyCore) {boolean disableOtaDexopt SystemProperties.getBoolean(config.disable_otadexopt,false);if (!disableOtaDexopt) {traceBeginAndSlog(StartOtaDexOptService);try {Watchdog.getInstance().pauseWatchingCurrentThread(moveab);OtaDexoptService.main(mSystemContext, mPackageManagerService);} catch (Throwable e) {reportWtf(starting OtaDexOptService, e);} finally {Watchdog.getInstance().resumeWatchingCurrentThread(moveab);traceEnd();}}}traceBeginAndSlog(StartUserManagerService);mSystemServiceManager.startService(UserManagerService.LifeCycle.class);traceEnd();// Initialize attribute cache used to cache resources from packages.traceBeginAndSlog(InitAttributerCache);AttributeCache.init(mSystemContext);traceEnd();// Set up the Application instance for the system process and get started.traceBeginAndSlog(SetSystemProcess);mActivityManagerService.setSystemProcess();traceEnd();// Complete the watchdog setup with an ActivityManager instance and listen for reboots// Do this only after the ActivityManagerService is properly started as a system processtraceBeginAndSlog(InitWatchdog);watchdog.init(mSystemContext, mActivityManagerService);traceEnd();// DisplayManagerService needs to setup android.display scheduling related policies// since setSystemProcess() would have overridden policies due to setProcessGroupmDisplayManagerService.setupSchedulerPolicies();// Manages Overlay packagestraceBeginAndSlog(StartOverlayManagerService);mSystemServiceManager.startService(new OverlayManagerService(mSystemContext, installer));traceEnd();traceBeginAndSlog(StartSensorPrivacyService);mSystemServiceManager.startService(new SensorPrivacyService(mSystemContext));traceEnd();if (SystemProperties.getInt(persist.sys.displayinset.top, 0) 0) {// DisplayManager needs the overlay immediately.mActivityManagerService.updateSystemUiContext();LocalServices.getService(DisplayManagerInternal.class).onOverlayChanged();}// The sensor service needs access to package manager service, app ops// service, and permissions service, therefore we start it after them.// Start sensor service in a separate thread. Completion should be checked// before using it.mSensorServiceStart SystemServerInitThreadPool.get().submit(() - {TimingsTraceLog traceLog new TimingsTraceLog(SYSTEM_SERVER_TIMING_ASYNC_TAG, Trace.TRACE_TAG_SYSTEM_SERVER);traceLog.traceBegin(START_SENSOR_SERVICE);startSensorService();traceLog.traceEnd();}, START_SENSOR_SERVICE);
}
4,startService
public T extends SystemService T startService(ClassT serviceClass) {try {final String name serviceClass.getName();Slog.i(TAG, Starting name);Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, StartService name);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);} catch (InstantiationException ex) {throw new RuntimeException(Failed to create service name : service could not be instantiated, ex);} catch (IllegalAccessException ex) {throw new RuntimeException(Failed to create service name : service must have a public constructor with a Context argument, ex);} catch (NoSuchMethodException ex) {throw new RuntimeException(Failed to create service name : service must have a public constructor with a Context argument, ex);} catch (InvocationTargetException ex) {throw new RuntimeException(Failed to create service name : service constructor threw an exception, ex);}//通过反射创建传递过来的Service对象调用startServicestartService(service);return service;} finally {Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);}
}public void startService(NonNull final SystemService service) {//将service添加到mServices中去mServices.add(service);long time SystemClock.elapsedRealtime();try {//调用service的onStart函数启动对应的serviceservice.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);}
拓展知识
LoadApk
LoadApk理解为apk文件加载到内存的一个java对象 framework-res.apk
context 对于Android context 大家是怎么理解的
LocalServices.java: addServece方法中 ArrayMap和HashMap的区别
ArrayMap k,v k是int类型的包装k是从小到大依次排列。时间复杂度可以是存的是 O(1). 取的过程就是log(n map.size). put和 get HashMap k(Object),v 时间复杂度 put和 get O(1). K是一个复合类型计算hash值 假如现在的k是String类型那么就需要遍历当前字符串 计算当前“jijs”字符串的hash值存储到对应的位置上去 对应时间复杂度O(k) k复杂增长 ArrayList ?
AMS、PMS是谁启动的他们都是独立的进程吗
他们是由system_server启动不是独立进程他们都运行在system_server进程中。
WatchDog 看门狗机制
原理是一个单例模式有一个handlerChecker集合根据handler进行监控监控所有的service 假如长时间未响应AMS handler sendMessageMQ时间戳
简述system_server的启动
Zygote调用forkSystemServer来创建system_server进程调用到Java层SystemServer.java.Main创建SystemServer的ActivityThread 创建framewok-res.apk的Application调用onCreate调用startBootstrapServices、startCoreServices、startOtherServices创建各种各样的ServiceAMS、PMS等,并开启开门狗检测服务和线程如果出现问题就会杀死system_serversystem_server死亡之后会通知Zygote, Zygote会杀死自己 通知init, init有线程守护会重启Zygote 并执行对应的onRestart服务。
总结
1.system_server是在Zygote启动的时候fork出来的子进程调用的是ZygoteInit.forkSystemServer,最终返回MethodAndArgsCaller包装的是com.android.server.SystemServer.Main。
2.SystemServer.Main函数直接调用了run函数在run函数中调用了createSystemContext通过ActivityThread.systemMain创建了ActivityThread设置了mSystemContext并且调用ActivityThread.attach 通过反射创建Application 执行onCreate函数.这里创建的app是framewok-res.apk是给系统使用的 比如系统的对话框。将mSystemServiceManager添加到LocalService的mService(ArrayMap)中去接着调用startBootstrapServices、startCoreServices、startOtherServices开启了非常多的服务Installer、ATMS、AMS、PMS等。把他们添加到SystemServiceManager的mServices(ArrayList)中去。
