Android SystemServer 启动流程

原文地址：

Android SystemServer学习

http://blog.csdn.NET/cloudwu007/article/details/6701765

Linux内核启动后，Android系统启动有4个步骤；

(1)init进程启动

(2)Native服务启动

(3)System Server及Java服务启动
(4)Home启动

Init进程启动后，将根据init.rc及initXXX.rc的内容执行一系列的命令，包括创建mount目录，安装文件系统，设置属性，启动adb,systemserver,mediaserver

system/core/rootdir/init.rc 内容如下

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# setup the global environment //设置环境变量

export PATH /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin

export LD_LIBRARY_PATH /vendor/lib:/system/lib

...

# Filesystem image public mount points. //mount文件系统

mkdir /mnt/obb 0700 root system

mount tmpfs tmpfs /mnt/obb mode=0755,gid=1000

...

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# Define the oom_adj values for the classes of processes that can be

# killed by the kernel. These are used in ActivityManagerService.

setprop ro.FOREGROUND_APP_ADJ 0

...

service servicemanager /system/bin/servicemanager //在其他服务启动前必须启动ServiceManager

class pre_zygote_services

user system

group system

critical

onrestart restart zygote

onrestart restart media

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service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server //启动SystemServer

class zygote_services

socket zygote stream 666

onrestart write /sys/android_power/request_state wake

onrestart write /sys/power/state on

onrestart restart media

onrestart restart netd

service media /system/bin/mediaserver //启动mediaserver,启动多媒体相关的camera/playback等服务

class zygote_services

user media

group system audio camera graphics inet net_bt net_bt_admin net_raw mot_drm input mot_tpapi mot_secclkd mot_pwric mot_caif

ioprio rt 4

代码中service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server将启动systemserver。



具体调用路径如下：

app_process主入口函数，启动system server时命令行为app_process -Xzygote /system/bin --zygote --start-system-server。

frameworks/base/cmds/app_process/app_main.cpp

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int main(int argc, const char* const argv[])

{

...

// Next arg is startup classname or "--zygote"

if (i < argc) {

arg = argv[i++];

if (0 == strcmp("--zygote", arg)) { //命令行必须含 --zygote

bool startSystemServer = (i < argc) ?

strcmp(argv[i], "--start-system-server") == 0 : false; //命令行是否含--start-system-server

setArgv0(argv0, "zygote");

set_process_name("zygote");

runtime.start("com.android.internal.os.ZygoteInit",

startSystemServer); //此处启动systemserver

} else {

...

}

启动ZygoteInit进程，以后所有的java进程均须通过此进程fork而成。

frameworks/base/core/jni/AndroidRuntime.cpp

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void AndroidRuntime::start(const char* className, const bool startSystemServer)

{

...

/* start the virtual machine */

if (startVm(&mJavaVM, &env) != 0)

goto bail;

/*

* Register android functions.

*/

if (startReg(env) < 0) {

LOGE("Unable to register all android natives\n");

goto bail;

}

...

if (startClass == NULL) {

LOGE("JavaVM unable to locate class '%s'\n", slashClassName);

/* keep going */

} else {

startMeth = env->GetStaticMethodID(startClass, "main",

"([Ljava/lang/String;)V");

if (startMeth == NULL) {

LOGE("JavaVM unable to find main() in '%s'\n", className);

/* keep going */

} else {

env->CallStaticVoidMethod(startClass, startMeth, strArray); //调用com.android.internal.os.ZygoteInit的main()方法

}

}

bail:

free(slashClassName);

}

ZygoteInit进程入口函数：

frameworks/base/core/java/com/android/internal/os/ZygoteInit.java

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public static void main(String argv[]) {

try {

VMRuntime.getRuntime().setMinimumHeapSize(5 * 1024 * 1024);

... registerZygoteSocket();

... preloadClasses();

... preloadResources();

// Do an initial gc to clean up after startup

gc();

...

if (argv[1].equals("true")) { //只支持true参数

startSystemServer(); //此处启动systemserver

}

...

if (ZYGOTE_FORK_MODE) { //目前为false

runForkMode();

} else {

runSelectLoopMode(); //将在Loop中顺序处理以后的For请求

}

closeServerSocket();

} catch (MethodAndArgsCaller caller) {

caller.run();

} catch (RuntimeException ex) {

Log.e(TAG, "Zygote died with exception", ex);

closeServerSocket();

throw ex;

}

}

启动system server。

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privatestatic boolean
startSystemServer()

throws MethodAndArgsCaller, RuntimeException {

/* Hardcoded command line to start the system
server */

String args[] = {

"--setuid=1000",

"--setgid=1000",

... "--capabilities=130104352,130104352",

"--runtime-init",

"--nice-name=system_server",

"com.android.server.SystemServer",//指定要启动的类名

};

ZygoteConnection.Arguments parsedArgs = null;...

try {

parsedArgs = new ZygoteConnection.Arguments(args);

...

/* Request to fork the system server process
*/

pid = Zygote.forkSystemServer( //fork出进程

parsedArgs.uid, parsedArgs.gid,

parsedArgs.gids, debugFlags, null,

parsedArgs.permittedCapabilities,

parsedArgs.effectiveCapabilities);

} catch (IllegalArgumentException
ex) {

throw new RuntimeException(ex);

}

/* For child process */

if (pid
== 0) {

handleSystemServerProcess(parsedArgs); //在fork出的进程里执行systemserver启动

}

return true;

}

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private static boolean startSystemServer()

throws MethodAndArgsCaller, RuntimeException {

/* Hardcoded command line to start the system server */

String args[] = {

"--setuid=1000",

"--setgid=1000",

... "--capabilities=130104352,130104352",

"--runtime-init",

"--nice-name=system_server",

"com.android.server.SystemServer", //指定要启动的类名

};

ZygoteConnection.Arguments parsedArgs = null;...

try {

parsedArgs = new ZygoteConnection.Arguments(args);

...

/* Request to fork the system server process */

pid = Zygote.forkSystemServer( //fork出进程

parsedArgs.uid, parsedArgs.gid,

parsedArgs.gids, debugFlags, null,

parsedArgs.permittedCapabilities,

parsedArgs.effectiveCapabilities);

} catch (IllegalArgumentException ex) {

throw new RuntimeException(ex);

}

/* For child process */

if (pid == 0) {

handleSystemServerProcess(parsedArgs); //在fork出的进程里执行systemserver启动

}

return true;

}

进程fork出来后，关闭socket并初始化进程

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private staticvoid handleSystemServerProcess(

ZygoteConnection.Arguments parsedArgs)

throws ZygoteInit.MethodAndArgsCaller {

closeServerSocket();

RuntimeInit.zygoteInit(parsedArgs.remainingArgs);

}

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private static void handleSystemServerProcess(

ZygoteConnection.Arguments parsedArgs)

throws ZygoteInit.MethodAndArgsCaller {

closeServerSocket();

RuntimeInit.zygoteInit(parsedArgs.remainingArgs);

}

所有java进程的共同入口zygoteInit()。

frameworks/base/core/java/com/android/internal/os/RuntimeInit.java

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public static final void zygoteInit(String[]
argv)

throws ZygoteInit.MethodAndArgsCaller {

...

commonInit(); //初始化时区，设置agent

zygoteInitNative(); //调用到com_android_internal_os_RuntimeInit_zygoteInit@AndroidRuntime.cpp
-> gCurRuntime->onZygoteInit()，此处启动ThreadPool

...

invokeStaticMain(startClass, startArgs); //调用com.android.server.SystemServer的main方法

}

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public static final void zygoteInit(String[] argv)

throws ZygoteInit.MethodAndArgsCaller {

...

commonInit(); //初始化时区，设置agent

zygoteInitNative(); //调用到com_android_internal_os_RuntimeInit_zygoteInit@AndroidRuntime.cpp -> gCurRuntime->onZygoteInit()，此处启动ThreadPool

...

invokeStaticMain(startClass, startArgs); //调用com.android.server.SystemServer的main方法

}

zygoteInitNative()将调用到JNI方法，并最终调用到onZygoteInit以启动进程池。

frameworks/base/cmds/app_process/app_main.cpp

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virtual void onZygoteInit()

{

sp<ProcessState> proc = ProcessState::self();

if (proc->supportsProcesses())
{

LOGV("App process: starting thread pool.\n");

proc->startThreadPool(); //启动线程池处理Binder事件

}

}

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virtual void onZygoteInit()

{

sp<ProcessState> proc = ProcessState::self();

if (proc->supportsProcesses()) {

LOGV("App process: starting thread pool.\n");

proc->startThreadPool(); //启动线程池处理Binder事件

}

}

systemServer进程主函数入口:

frameworks/base/services/java/com/android/server/SystemServer.java

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public staticvoid main(String[]
args) {

// The system server has to run all of the time, so
it needs to be

// as efficient as possible with its memory usage.

VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);

System.loadLibrary("android_servers");//Load
JNI library here that is used by SystemServer

init1(args); //这里调用到android_server_SystemServer_init1@com_android_server_SystemServer.cpp

}

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public static void main(String[] args) {

// The system server has to run all of the time, so it needs to be

// as efficient as possible with its memory usage.

VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);

System.loadLibrary("android_servers"); //Load JNI library here that is used by SystemServer

init1(args); //这里调用到android_server_SystemServer_init1@com_android_server_SystemServer.cpp

}

systemServer初始化函数1，用来启动进程内所有的native服务，因为其他java服务依赖这些服务。

frameworks/base/services/jni/com_android_server_SystemServer.cpp

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static void android_server_SystemServer_init1(JNIEnv*
env, jobject clazz)

{

system_init();

}

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static void android_server_SystemServer_init1(JNIEnv* env, jobject clazz)

{

system_init();

}

frameworks/base/cmds/system_server/library/system_init.cpp

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extern "C" status_t
system_init()

{

sp<ProcessState> proc(ProcessState::self());

sp<IServiceManager> sm = defaultServiceManager();

LOGI("ServiceManager: %p\n",
sm.get());

sp<GrimReaper> grim = new GrimReaper();

sm->asBinder()->linkToDeath(grim, grim.get(), 0);

char propBuf[PROPERTY_VALUE_MAX];

property_get("system_init.startsurfaceflinger",
propBuf,"1");

if (strcmp(propBuf, "1")
== 0) { //可以通过改变属性来设置SurfaceFlinger是否run在systemserver里

// Start the SurfaceFlinger

SurfaceFlinger::instantiate();

}

// Start the sensor service

SensorService::instantiate(); //启动SensorService

// On the simulator, audioflinger et al don't get
started the

// same way as on the device, and we need to start
them here

if (!proc->supportsProcesses())
{//在phone上，这些service在mediaserver中创建。模拟器上，以下service在此进程创建

// Start the AudioFlinger

AudioFlinger::instantiate();

// Start the media playback service

MediaPlayerService::instantiate();

// Start the camera service

CameraService::instantiate();

// Start the audio policy service

AudioPolicyService::instantiate();

}

AndroidRuntime* runtime = AndroidRuntime::getRuntime();

runtime->callStatic("com/android/server/SystemServer","init2");//调用init2@SystemServer.java，在这里创建工作线程以启动各java服务并进入循环处理各service请求

if (proc->supportsProcesses())
{

ProcessState::self()->startThreadPool(); //启动线程池，注意：由于前面已经调用过startThreadPool,故此次调用不做任何事情

IPCThreadState::self()->joinThreadPool(); //主线程加入到线程池里

}

return NO_ERROR;

}

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extern "C" status_t system_init()

{

sp<ProcessState> proc(ProcessState::self());

sp<IServiceManager> sm = defaultServiceManager();

LOGI("ServiceManager: %p\n", sm.get());

sp<GrimReaper> grim = new GrimReaper();

sm->asBinder()->linkToDeath(grim, grim.get(), 0);

char propBuf[PROPERTY_VALUE_MAX];

property_get("system_init.startsurfaceflinger", propBuf, "1");

if (strcmp(propBuf, "1") == 0) { //可以通过改变属性来设置SurfaceFlinger是否run在systemserver里

// Start the SurfaceFlinger

SurfaceFlinger::instantiate();

}

// Start the sensor service

SensorService::instantiate(); //启动SensorService

// On the simulator, audioflinger et al don't get started the

// same way as on the device, and we need to start them here

if (!proc->supportsProcesses()) { //在phone上，这些service在mediaserver中创建。模拟器上，以下service在此进程创建

// Start the AudioFlinger

AudioFlinger::instantiate();

// Start the media playback service

MediaPlayerService::instantiate();

// Start the camera service

CameraService::instantiate();

// Start the audio policy service

AudioPolicyService::instantiate();

}

AndroidRuntime* runtime = AndroidRuntime::getRuntime();

runtime->callStatic("com/android/server/SystemServer", "init2");//调用init2@SystemServer.java，在这里创建工作线程以启动各java服务并进入循环处理各service请求

if (proc->supportsProcesses()) {

ProcessState::self()->startThreadPool(); //启动线程池，注意：由于前面已经调用过startThreadPool,故此次调用不做任何事情

IPCThreadState::self()->joinThreadPool(); //主线程加入到线程池里

}

return NO_ERROR;

}

进程初始化函数init2，用来启动进程内所有的java服务。

frameworks/base/services/java/com/android/server/SystemServer.java

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public class SystemServer

{

public static finalvoid init2()
{

Slog.i(TAG, "Entered the Android system server!");

Thread thr = new ServerThread(); //创建新线程

thr.setName("android.server.ServerThread");

thr.start(); //启动工作线程，在此线程启动各种服务

}

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public class SystemServer

{

public static final void init2() {

Slog.i(TAG, "Entered the Android system server!");

Thread thr = new ServerThread(); //创建新线程

thr.setName("android.server.ServerThread");

thr.start(); //启动工作线程，在此线程启动各种服务

}

此工作线程(线程1)实现Java Service注册初始化及进入SystemServer事件处理循环。

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class ServerThread
extends Thread {

@Override

public void run()
{

Looper.prepare(); //在此线程内处理system server相关消息

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

BinderInternal.disableBackgroundScheduling(true);

android.os.Process.setCanSelfBackground(false);

// Critical services...

try {

ServiceManager.addService("entropy",new EntropyService());//注册Service到ServiceManager

power = new PowerManagerService();

ServiceManager.addService(Context.POWER_SERVICE, power);

context = ActivityManagerService.main(factoryTest); //注意：此处启动ActivityManagerService

...

pm = PackageManagerService.main(context,factoryTest != SystemServer.FACTORY_TEST_OFF);

ActivityManagerService.setSystemProcess();

...

ContentService.main(context,factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);

ActivityManagerService.installSystemProviders()

...

wm = WindowManagerService.main(context, power,factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL);//启动Windows
Manager

ServiceManager.addService(Context.WINDOW_SERVICE, wm);

((ActivityManagerService)ServiceManager.getService("activity")).setWindowManager(wm);

...

wm.systemReady(); //通知SystemReady

power.systemReady();

try {

pm.systemReady();

} catch (RemoteException
e) {

}

...

// We now tell the activity manager it is okay
to run third party

// code. It will call back into us once it has
gotten to the state

// where third party code can really run (but
before it has actually

// started launching the initial applications),
for us to complete our

// initialization.

((ActivityManagerService)ActivityManagerNative.getDefault())

.systemReady(new Runnable()
{

public void run()
{

if (statusBarF
!= null) statusBarF.systemReady2();

if (batteryF
!= null) batteryF.systemReady();

if (connectivityF
!= null) connectivityF.systemReady();

if (dockF
!= null) dockF.systemReady();

if (usbF
!= null) usbF.systemReady();

if (uiModeF
!= null) uiModeF.systemReady();

if (recognitionF
!= null) recognitionF.systemReady();

Watchdog.getInstance().start();

// It is now okay to let the various system
services start their

// third party code...

if (appWidgetF
!= null) appWidgetF.systemReady(safeMode);

if (wallpaperF
!= null) wallpaperF.systemReady();

if (immF
!= null) immF.systemReady();

if (locationF
!= null) locationF.systemReady();

if (throttleF
!= null) throttleF.systemReady();

}

...

Looper.loop(); //进入循环，处理请求

}

}

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class ServerThread extends Thread {

@Override

public void run() {

Looper.prepare(); //在此线程内处理system server相关消息

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

BinderInternal.disableBackgroundScheduling(true);

android.os.Process.setCanSelfBackground(false);

// Critical services...

try {

ServiceManager.addService("entropy", new EntropyService()); //注册Service到ServiceManager

power = new PowerManagerService();

ServiceManager.addService(Context.POWER_SERVICE, power);

context = ActivityManagerService.main(factoryTest); //注意：此处启动ActivityManagerService

...

pm = PackageManagerService.main(context,factoryTest != SystemServer.FACTORY_TEST_OFF);

ActivityManagerService.setSystemProcess();

...

ContentService.main(context,factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);

ActivityManagerService.installSystemProviders()

...

wm = WindowManagerService.main(context, power,factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL); //启动Windows Manager

ServiceManager.addService(Context.WINDOW_SERVICE, wm);

((ActivityManagerService)ServiceManager.getService("activity")).setWindowManager(wm);

...

wm.systemReady(); //通知SystemReady

power.systemReady();

try {

pm.systemReady();

} catch (RemoteException e) {

}

...

// We now tell the activity manager it is okay to run third party

// code. It will call back into us once it has gotten to the state

// where third party code can really run (but before it has actually

// started launching the initial applications), for us to complete our

// initialization.

((ActivityManagerService)ActivityManagerNative.getDefault())

.systemReady(new Runnable() {

public void run() {

if (statusBarF != null) statusBarF.systemReady2();

if (batteryF != null) batteryF.systemReady();

if (connectivityF != null) connectivityF.systemReady();

if (dockF != null) dockF.systemReady();

if (usbF != null) usbF.systemReady();

if (uiModeF != null) uiModeF.systemReady();

if (recognitionF != null) recognitionF.systemReady();

Watchdog.getInstance().start();

// It is now okay to let the various system services start their

// third party code...

if (appWidgetF != null) appWidgetF.systemReady(safeMode);

if (wallpaperF != null) wallpaperF.systemReady();

if (immF != null) immF.systemReady();

if (locationF != null) locationF.systemReady();

if (throttleF != null) throttleF.systemReady();

}

...

Looper.loop(); //进入循环，处理请求

}

}

ActivityManagerService主入口：

frameworks/base/services/java/com/android/server/am/ActivityManagerService.java

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<span style="font-size:18px;"> publicstaticfinal Context
main(int factoryTest) {

AThread thr = new AThread(); //创建工作线程2

thr.start(); //启动线程

synchronized (thr)
{//等待</span><span style="font-size:16px;"><span style="font-size:18px;">ActivityManagerService对象创建完成

while (thr.mService
== null) {

try {

thr.wait();

} catch (InterruptedException
e) {

}

}

}</span>

ActivityManagerService m = thr.mService;

mSelf = m;

ActivityThread at = ActivityThread.systemMain(); //加载system应用，并把此线程（工作线程1）作为SystemServer进程的system线程

mSystemThread = at;

Context context = at.getSystemContext();

m.mContext = context;

m.mFactoryTest = factoryTest;

m.mMainStack = new ActivityStack(m,
context,true);

m.mBatteryStatsService.publish(context);

m.mUsageStatsService.publish(context);

synchronized (thr)
{

thr.mReady = true;

thr.notifyAll();

}

m.startRunning(null,null,null,null);//初始化变量并设置system
ready为true

return context;

}</span>

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<span style="font-size:18px;"> public static final Context main(int factoryTest) {

AThread thr = new AThread(); //创建工作线程2

thr.start(); //启动线程

synchronized (thr) { //等待</span><span style="font-size:16px;"><span style="font-size:18px;">ActivityManagerService对象创建完成

while (thr.mService == null) {

try {

thr.wait();

} catch (InterruptedException e) {

}

}

}</span>

ActivityManagerService m = thr.mService;

mSelf = m;

ActivityThread at = ActivityThread.systemMain(); //加载system应用，并把此线程（工作线程1）作为SystemServer进程的system线程

mSystemThread = at;

Context context = at.getSystemContext();

m.mContext = context;

m.mFactoryTest = factoryTest;

m.mMainStack = new ActivityStack(m, context, true);

m.mBatteryStatsService.publish(context);

m.mUsageStatsService.publish(context);

synchronized (thr) {

thr.mReady = true;

thr.notifyAll();

}

m.startRunning(null, null, null, null); //初始化变量并设置system ready为true

return context;

}</span>

线程2中作为ActivityManager的工作线程，在其中处理ActivityManager相关的消息。

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static class AThreadextends Thread
{

ActivityManagerService mService;

boolean mReady
= false;

public AThread()
{

super("ActivityManager");

}

public void run()
{

Looper.prepare();

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

android.os.Process.setCanSelfBackground(false);

ActivityManagerService m = new ActivityManagerService();

synchronized (this)
{

mService = m;

notifyAll();

}

synchronized (this)
{

while (!mReady)
{

try {

wait();

} catch (InterruptedException
e) {

}

}

}

Looper.loop();

}

}

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static class AThread extends Thread {

ActivityManagerService mService;

boolean mReady = false;

public AThread() {

super("ActivityManager");

}

public void run() {

Looper.prepare();

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

android.os.Process.setCanSelfBackground(false);

ActivityManagerService m = new ActivityManagerService();

synchronized (this) {

mService = m;

notifyAll();

}

synchronized (this) {

while (!mReady) {

try {

wait();

} catch (InterruptedException e) {

}

}

}

Looper.loop();

}

}

ActivityThread.systemMain(）将加载系统应用apk：

ActivityThread.java

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public static final ActivityThread
systemMain() {

ActivityThread thread = new ActivityThread();

thread.attach(true); //加载system应用

return thread;

}

private finalvoid attach(boolean system)
{

sThreadLocal.set(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.

android.ddm.DdmHandleAppName.setAppName("system_process");

try {

mInstrumentation = new Instrumentation();

ContextImpl context = new ContextImpl();

context.init(getSystemContext().mPackageInfo, null, this);

Application app = Instrumentation.newApplication(Application.class,
context);//创建Application对象并实例化android.app.Application对象

mAllApplications.add(app);

mInitialApplication = app;

app.onCreate(); //调用onCreate

} catch (Exception
e) {

throw new RuntimeException(

"Unable to instantiate Application():" +
e.toString(), e);

}

}

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public static final ActivityThread systemMain() {

ActivityThread thread = new ActivityThread();

thread.attach(true); //加载system应用

return thread;

}

private final void attach(boolean system) {

sThreadLocal.set(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.

android.ddm.DdmHandleAppName.setAppName("system_process");

try {

mInstrumentation = new Instrumentation();

ContextImpl context = new ContextImpl();

context.init(getSystemContext().mPackageInfo, null, this);

Application app = Instrumentation.newApplication(Application.class, context); //创建Application对象并实例化android.app.Application对象

mAllApplications.add(app);

mInitialApplication = app;

app.onCreate(); //调用onCreate

} catch (Exception e) {

throw new RuntimeException(

"Unable to instantiate Application():" + e.toString(), e);

}

}

ActivityManagerService.java

[java] view
plaincopy

public finalvoid startRunning(String
pkg, String cls, String action,

String data) {

synchronized(this)
{

if (mStartRunning)
{

return;

}

mStartRunning = true;

mTopComponent = pkg != null &&
cls !=null

? new ComponentName(pkg,
cls) :null;

mTopAction = action != null ?
action : Intent.ACTION_MAIN;

mTopData = data;

if (!mSystemReady)
{

return;

}

}

systemReady(null); //设置system
ready为true,但此句似乎无用因为mSystemReady此时必然为true，故调用systemReady(null)什么事也不做

}

[java] view
plain copy

public final void startRunning(String pkg, String cls, String action,

String data) {

synchronized(this) {

if (mStartRunning) {

return;

}

mStartRunning = true;

mTopComponent = pkg != null && cls != null

? new ComponentName(pkg, cls) : null;

mTopAction = action != null ? action : Intent.ACTION_MAIN;

mTopData = data;

if (!mSystemReady) {

return;

}

}

systemReady(null); //设置system ready为true,但此句似乎无用因为mSystemReady此时必然为true，故调用systemReady(null)什么事也不做

}

[java] view
plaincopy

public void systemReady(final Runnable
goingCallback) {...

synchronized(this)
{

if (mSystemReady)
{

if (goingCallback
!=null) goingCallback.run(); //如果有Runnable要运行

return;

}

// Check to see if there are any update receivers
to run.

if (!mDidUpdate)
{

if (mWaitingUpdate)
{

return;

}

Intent intent = new Intent(Intent.ACTION_PRE_BOOT_COMPLETED);

List<ResolveInfo> ris = null;

try {

ris = AppGlobals.getPackageManager().queryIntentReceivers(

intent, null, 0);

} catch (RemoteException
e) {

}

if (ris
!= null) {

for (int i=ris.size()-1;
i>=0; i--) {

if ((ris.get(i).activityInfo.applicationInfo.flags

&ApplicationInfo.FLAG_SYSTEM) ==0)
{

ris.remove(i);

}

}

intent.addFlags(Intent.FLAG_RECEIVER_BOOT_UPGRADE);

ArrayList<ComponentName> lastDoneReceivers = readLastDonePreBootReceivers();

final ArrayList<ComponentName>
doneReceivers =new ArrayList<ComponentName>();

for (int i=0;
i<ris.size(); i++) {

ActivityInfo ai = ris.get(i).activityInfo;

ComponentName comp = new ComponentName(ai.packageName,
ai.name);

if (lastDoneReceivers.contains(comp))
{

ris.remove(i);

i--;

}

}

for (int i=0;
i<ris.size(); i++) {

ActivityInfo ai = ris.get(i).activityInfo;

ComponentName comp = new ComponentName(ai.packageName,
ai.name);

doneReceivers.add(comp);

intent.setComponent(comp);

IIntentReceiver finisher = null;

if (i
== ris.size()-1) {

finisher = new IIntentReceiver.Stub()
{

publicvoid performReceive(Intent
intent,int resultCode,

String data, Bundle extras, boolean ordered,

boolean sticky)
{

// The raw IIntentReceiver
interface is called

// with the AM lock
held, so redispatch to

// execute our code
without the lock.

mHandler.post(new Runnable()
{

publicvoid run()
{

synchronized (ActivityManagerService.this)
{

mDidUpdate = true;

}

writeLastDonePreBootReceivers(doneReceivers);

systemReady(goingCallback);

}

});

}

};

}

broadcastIntentLocked(null,null,
intent,null, finisher,

0, null, null,null,true,false,
MY_PID, Process.SYSTEM_UID);

if (finisher
!=null) {

mWaitingUpdate = true;

}

}

}

if (mWaitingUpdate)
{

return;

}

mDidUpdate = true;

}

mSystemReady = true; //置位

// silent reboot bit will be off on normal
power down

if (mContext.getResources().getBoolean(com.android.internal.R.bool.config_poweron_sound))
{

ConfigInfo.pwrSnd_setSilentreboot(1);

} else if (mContext.getResources()

.getBoolean(com.android.internal.R.bool.config_mute_poweron_sound)) {

// Request that the next BootAnimation
plays its sound.

ConfigInfo.pwrSnd_setSilentreboot(0);

}

if (!mStartRunning)
{ //如果ActivityManagerService.startRunning已运行过，则无需继续

return;

}

}

ArrayList<ProcessRecord> procsToKill = null;

synchronized(mPidsSelfLocked)
{

for (int i=mPidsSelfLocked.size()-1;
i>=0; i--) {

ProcessRecord proc = mPidsSelfLocked.valueAt(i);

if (!isAllowedWhileBooting(proc.info)){//检查FLAG_PERSISTENT是否为真

if (procsToKill
==null) {

procsToKill = new ArrayList<ProcessRecord>();

}

procsToKill.add(proc); //如果应用未指明为persistent，则不能在system
ready前运行

}

}

}

synchronized(this)
{

if (procsToKill
!=null) {

for (int i=procsToKill.size()-1;
i>=0; i--) {

ProcessRecord proc = procsToKill.get(i);

Slog.i(TAG, "Removing system update proc: " +
proc);

removeProcessLocked(proc, true); //杀掉所有已运行的非persistent应用

}

}

// Now that we have cleaned up any update
processes, we

// are ready to start launching real processes
and know that

// we won't trample on them any more.

mProcessesReady = true; //为真时，才允许launch正常的应用

}...

synchronized(this)
{

// Make sure we have no pre-ready processes
sitting around.

...

retrieveSettings();

if (goingCallback
!=null) goingCallback.run();

synchronized (this)
{

if (mFactoryTest
!= SystemServer.FACTORY_TEST_LOW_LEVEL) {

try {

List apps = AppGlobals.getPackageManager().

getPersistentApplications(STOCK_PM_FLAGS);

if (apps
!= null) {

int N
= apps.size();

int i;

for (i=0;
i<N; i++) {

ApplicationInfo info

= (ApplicationInfo)apps.get(i);

if (info
!=null &&

!info.packageName.equals("android"))
{

addAppLocked(info); //启动所有标为persistent的且package名字为android的应用

}

}

}

} catch (RemoteException
ex) {

// pm is in same process, this will
never happen.

}

}

// Start up initial activity.

mBooting = true;

try {

if (AppGlobals.getPackageManager().hasSystemUidErrors())
{//如果/data/system文件夹的uid和当前system UID不匹配

Message msg = Message.obtain();

msg.what = SHOW_UID_ERROR_MSG;

mHandler.sendMessage(msg);

}

} catch (RemoteException
e) {

}

mMainStack.resumeTopActivityLocked(null);//启动初始进程Home

}

}