Binder篇_02system_server進程的創(chuàng)建

目標:

1. system_server進程的創(chuàng)建;
2. AMS的創(chuàng)建以及核心服務(wù)的注冊;
3. App進程何時創(chuàng)建;
4. App進程的Binder線程何時創(chuàng)建;
5. App線程何時創(chuàng)建;
6. Application.attachBaseContext()方法為什么不會ANR;

圍繞這幾個問題分幾篇筆記進行分析;

這篇筆記主要包括以下幾個點

1. system_server進程的創(chuàng)建;
2. binder線程的創(chuàng)建;
3. SSM的創(chuàng)建;
4. PMS的創(chuàng)建;
5. AMS的創(chuàng)建;
6. 通過SM進行服務(wù)的注冊;

一、參考文章:

1. Android系統(tǒng)開篇;
2. Android系統(tǒng)啟動-zygote篇;
3. Android系統(tǒng)啟動-SystemServer上篇;
4. Android系統(tǒng)啟動-SystemServer下篇;
5. Binder系列3—啟動ServiceManager;
6. 理解Android進程創(chuàng)建流程;

二、相關(guān)源碼地址:

三、Android系統(tǒng)啟動流程 :

進程啟動流程圖

android系統(tǒng)啟動流程圖
序號 進程啟動 概述
1 init進程 Linux系統(tǒng)中用戶空間的第一個進程
2 Zygote進程 所有App進程的父進程
3 system_server進程 系統(tǒng)各大服務(wù)的載體
4 ServiceManager進程 Binder服務(wù)的大管家, 守護進程循環(huán)運行在binder_loop
5 APP進程 通過Process.start啟動APP進程
system_server進程創(chuàng)建流程圖

四、system_server進程

4.1 ZygoteInit.main((Zygote進程))
public static void main(String argv[]) {
    try {
        boolean startSystemServer = false;
        String socketName = "zygote";
        String abiList = null;
        for (int i = 1; i < argv.length; i++) {
            if ("start-system-server".equals(argv[i])) {
                startSystemServer = true;
            } else if (argv[i].startsWith(ABI_LIST_ARG)) {
                abiList = argv[i].substring(ABI_LIST_ARG.length());
            } else if (argv[i].startsWith(SOCKET_NAME_ARG)) {
                socketName = argv[i].substring(SOCKET_NAME_ARG.length());
            }
        }
        // 為Zygote注冊socket, 為了后續(xù)system_server進程通過socket與zygote進程進行通信;
        registerZygoteSocket(socketName);      
        // 進行資源的預(yù)加載, 在談jvm與dvm的區(qū)別時, 提到的一些概念涉及到這里, Zygote進程創(chuàng)建時
        // 會進行部分資源的預(yù)加載, 然后在fork創(chuàng)建子進程時, 直接拷貝這些資源;
        preload();                
        if (startSystemServer) {
            // 這里進行system_server進程的創(chuàng)建, 傳入socketName, 方便后續(xù)system_server進程與
            // zygote進程進行通信;
            startSystemServer(abiList, socketName);              
        }
        // 進程創(chuàng)建完成以后, zygote進程便會進入休眠狀態(tài), 利用io多路復用機制監(jiān)聽文件描述符;
        runSelectLoop(abiList);     
    } catch (MethodAndArgsCaller caller) {
        // 在創(chuàng)建system_server和app進程時, 都會通過拋MethodAndArgsCaller來觸發(fā)這里caller.run的執(zhí)行;
        caller.run();
    }
}
4.2 ZygoteInit.startSystemServer(Zygote進程)
private static boolean startSystemServer(String abiList, String socketName) throws MethodAndArgsCaller {
    String args[] = {
        "--setuid=1000",
        "--setgid=1000",
        "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1032,3001,3002,3003,3006,3007",
        "--capabilities=" + capabilities + "," + capabilities,
        "--nice-name=system_server",
        "--runtime-args",
        "com.android.server.SystemServer",
    };
    ZygoteConnection.Arguments parsedArgs = null;
    int pid;
    parsedArgs = new ZygoteConnection.Arguments(args);
    ZygoteConnection.applyDebuggerSystemProperty(parsedArgs);
    ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs);
    // 知道這里是fork方式以Zygote進程為父進程創(chuàng)建的system_server子進程即可;
    pid = Zygote.forkSystemServer(
                    parsedArgs.uid, parsedArgs.gid,
                    parsedArgs.gids,
                    parsedArgs.debugFlags,
                    null,
                    parsedArgs.permittedCapabilities,
                    parsedArgs.effectiveCapabilities);

    if (pid == 0) {
        // system_server進程創(chuàng)建完成以后, 開始處理system_server進程的相關(guān)邏輯;
        handleSystemServerProcess(parsedArgs);
    }
    return true;
}
4.3 ZygoteInit.handleSystemServerProcess(system_server進程)
private static void handleSystemServerProcess(ZygoteConnection.Arguments parsedArgs)
            throws ZygoteInit.MethodAndArgsCaller {
    if (parsedArgs.invokeWith != null) {
        ...
    } else {
        ClassLoader cl = null;
        if (systemServerClasspath != null) {
            // 注意這里初始化了PathClassLoader, 后續(xù)App進程創(chuàng)建時也需要注意;
            cl = new PathClassLoader(systemServerClasspath, ClassLoader.getSystemClassLoader());
            Thread.currentThread().setContextClassLoader(cl);
        }
        RuntimeInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs, cl);  
    }
}
4.4 RuntimeInit.zygoteInit
private static final native void nativeZygoteInit();

public static final void zygoteInit(int targetSdkVersion, String[] argv, ClassLoader classLoader)
            throws ZygoteInit.MethodAndArgsCaller {
    ...
    // 進行常規(guī)初始化操作, 這里暫時不進行任何分析;
    commonInit();
    // 這里會觸發(fā)Binder線程的創(chuàng)建;
    nativeZygoteInit();
    // 到這里已經(jīng)完成了system_server進程的創(chuàng)建, system_server對應(yīng)的Binder線程的創(chuàng)建;  
    applicationInit(targetSdkVersion, argv, classLoader);
}
4.5 AndroidRuntime.com_android_internal_os_RuntimeInit_nativeZygoteInit
static void com_android_internal_os_RuntimeInit_nativeZygoteInit(JNIEnv* env, jobject clazz)
{
    // 觸發(fā)app_main.onZygoteInit()方法的執(zhí)行;
    gCurRuntime->onZygoteInit();
}
4.6 app_main.onZygoteInit
virtual void onZygoteInit()
{
    sp<ProcessState> proc = ProcessState::self();
    ALOGV("App process: starting thread pool.\n");
    // 知道這里是創(chuàng)建Binder線程即可, 至于線程創(chuàng)建細節(jié), 感覺沒必要知道;
    // 內(nèi)部就是調(diào)用了new PoolThread().start()操作;
    proc->startThreadPool();
}
4.7 RuntimeInit.applicationInit
private static void applicationInit(int targetSdkVersion, String[] argv, ClassLoader classLoader)
            throws ZygoteInit.MethodAndArgsCaller {
    final Arguments args;
    args = new Arguments(argv);
    // 通過對ZygoteInit.startSystemServer()的分析可知, 這里會觸發(fā)SystemServer.main的執(zhí)行;
    invokeStaticMain(args.startClass, args.startArgs, classLoader);
}
4.8 SystemServer.main
public static void main(String[] args) {
    new SystemServer().run();
}
4.9 SystemServer.run
private void run() {
    Looper.prepareMainLooper();
    // Initialize native services.
    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.
    createSystemContext();
    // 初始化SSM
    mSystemServiceManager = new SystemServiceManager(mSystemContext);
    LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
    // Start services.
    startBootstrapServices();
    startCoreServices();
    startOtherServices();
    // Loop forever.
    Looper.loop();
}
4.10 SystemServer.startBootstrapServices
private void startBootstrapServices() {
    
    mActivityManagerService = mSystemServiceManager.startService(
                ActivityManagerService.Lifecycle.class).getService();
    // 創(chuàng)建AMS, AMS在system_server進程中創(chuàng)建的證據(jù);
    mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
    // 創(chuàng)建PMS, PMS也是在system_server進程中創(chuàng)建的;
    mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
                mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
    mPackageManager = mSystemContext.getPackageManager();
    // 這里的操作是非常關(guān)鍵的, 后期Activity啟動流程離不開這里的操作;
    mActivityManagerService.setSystemProcess();
}
4.11 ActivityManagerService.setSystemProcess
public void setSystemProcess() {
    // Context.ACTIVITY_SERVICE = "activity";
    // ProcessStats.SERVICE_NAME = "procstats";
    ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
    ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
    ServiceManager.addService("meminfo", new MemBinder(this));
    ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
    ServiceManager.addService("dbinfo", new DbBinder(this));
    if (MONITOR_CPU_USAGE) {
        ServiceManager.addService("cpuinfo", new CpuBinder(this));
    }
    ServiceManager.addService("permission", new PermissionController(this));
    ServiceManager.addService("processinfo", new ProcessInfoService(this));
    ApplicationInfo info = mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS);
    mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
    synchronized (this) {
        ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);
        app.persistent = true;
        app.pid = MY_PID;
        app.maxAdj = ProcessList.SYSTEM_ADJ;
        app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
        synchronized (mPidsSelfLocked) {
            mPidsSelfLocked.put(app.pid, app);
        }
        updateLruProcessLocked(app, false, null);
        updateOomAdjLocked();
    }
}
4.12 ServiceManager.addService
public static void addService(String name, IBinder service) {
    // getIServiceManager()通過SMN返回SMP, 注意這里的寫法, 后續(xù)啟動Activity時, 也是類似這種寫法
    // AMN觸發(fā)AMP;
    getIServiceManager().addService(name, service, false);
}
private static IServiceManager getIServiceManager() {
    if (sServiceManager != null) {
        return sServiceManager;
    }
    // sServiceManager指向的是SMP, 再次記住, 這里還是system_server進程;
    // 這里只需要記住BinderInternal.getContextObject()返回的是BinderProxy;
    sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
    return sServiceManager;
}
4.13 SMP.addService(這里通過添加服務(wù))
// 這里有幾個點需要注意一下, service指向的是ActivityManagerService, 最終通過BinderProxy, 將數(shù)據(jù)
// 以及AMS傳給Native層;
public void addService(String name, IBinder service, boolean allowIsolated) {
    Parcel data = Parcel.obtain();
    Parcel reply = Parcel.obtain();
    data.writeInterfaceToken(IServiceManager.descriptor);
    data.writeString(name);
    data.writeStrongBinder(service);
    data.writeInt(allowIsolated ? 1 : 0);
    // mRemote指向的是BinderProxy;
    mRemote.transact(ADD_SERVICE_TRANSACTION, data, reply, 0);
    reply.recycle();
    data.recycle();
}
最后編輯于 ：
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

推薦閱讀更多精彩內(nèi)容