Android systemserver分析ThrottleService 介绍

System Server是Android系统的核心，他在Dalvik虚拟机启动后立即开始初始化和运行。其它的系统服务在System Server进程的环境中运行。/base/services/java/com/android/server/SystemServer.java

Java代码


/**

* This method is called from Zygote to initialize the system. This will cause the native

* services (SurfaceFlinger, AudioFlinger, etc..) to be started. After that it will call back

* up into init2() to start the Android services.

*/

native public static void init1(String[] args);

public static void main(String[] args) {

if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {

// If a device's clock is before 1970 (before 0), a lot of

// APIs crash dealing with negative numbers, notably

// java.io.File#setLastModified, so instead we fake it and

// hope that time from cell towers or NTP fixes it

// shortly.

Slog.w(TAG, "System clock is before 1970; setting to 1970." );

SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);

}

if (SamplingProfilerIntegration.isEnabled()) {

SamplingProfilerIntegration.start();

timer = new Timer();

timer.schedule(new TimerTask() {

@Override

public void run() {

SamplingProfilerIntegration.writeSnapshot("system_server" );

}

}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);

}

// 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" );

init1(args);

}

public static final void init2() {

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

Thread thr = new ServerThread();

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

thr.start();

}

在main函数中，首先检查系统时间设置和SamplingProfiler。然后加载一个叫android_servers的本地库，他提供本 地方法的接口（源程序在framework/base/services/jni/目录中）。然后调用本地方法设置服务。具体执行设置的代码在 frameworks/base/cmds/system_server/library/system_init.cpp中。

C代码


extern "C" status_t system_init()

{

LOGI("Entered 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) {

// Start the SurfaceFlinger

SurfaceFlinger::instantiate();

}

// Start the sensor service

SensorService::instantiate();

// 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()) {

// 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();

}

// And now start the Android runtime. We have to do this bit

// of nastiness because the Android runtime initialization requires

// some of the core system services to already be started.

// All other servers should just start the Android runtime at

// the beginning of their processes's main(), before calling

// the init function.

LOGI("System server: starting Android runtime.\n" );

AndroidRuntime* runtime = AndroidRuntime::getRuntime();

LOGI("System server: starting Android services.\n" );

runtime->callStatic("com/android/server/SystemServer" , "init2" );

// If running in our own process, just go into the thread

// pool. Otherwise, call the initialization finished

// func to let this process continue its initilization.

if (proc->supportsProcesses()) {

LOGI("System server: entering thread pool.\n" );

ProcessState::self()->startThreadPool();

IPCThreadState::self()->joinThreadPool();

LOGI("System server: exiting thread pool.\n" );

}

return NO_ERROR;

}

等初始化传感器，视频，音频等服务后，调用一个回调方法init2 (在SystemServer.java中)。在上面的代码可以看到，这个方法开启了ServerThread来初始化其它的服务。

Java代码


public void run() {

EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN,

SystemClock.uptimeMillis());

Looper.prepare();

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

BinderInternal.disableBackgroundScheduling(true );

android.os.Process.setCanSelfBackground(false );

// Check whether we failed to shut down last time we tried.

{

final String shutdownAction = SystemProperties.get(

ShutdownThread.SHUTDOWN_ACTION_PROPERTY, "" );

if (shutdownAction != null && shutdownAction.length() > 0 ) {

boolean reboot = (shutdownAction.charAt( 0 ) == '1' );

final String reason;

if (shutdownAction.length() > 1 ) {

reason = shutdownAction.substring(1 , shutdownAction.length());

} else {

reason = null ;

}

ShutdownThread.rebootOrShutdown(reboot, reason);

}

}

String factoryTestStr = SystemProperties.get("ro.factorytest" );

int factoryTest = "" .equals(factoryTestStr) ? SystemServer.FACTORY_TEST_OFF

: Integer.parseInt(factoryTestStr);

LightsService lights = null ;

PowerManagerService power = null ;

BatteryService battery = null ;

ConnectivityService connectivity = null ;

IPackageManager pm = null ;

Context context = null ;

WindowManagerService wm = null ;

BluetoothService bluetooth = null ;

BluetoothA2dpService bluetoothA2dp = null ;

HeadsetObserver headset = null ;

DockObserver dock = null ;

UsbService usb = null ;

UiModeManagerService uiMode = null ;

RecognitionManagerService recognition = null ;

ThrottleService throttle = null ;

// Critical services...

try {

Slog.i(TAG, "Entropy Service" );

ServiceManager.addService("entropy" , new EntropyService());

Slog.i(TAG, "Power Manager" );

power = new PowerManagerService();

ServiceManager.addService(Context.POWER_SERVICE, power);

Slog.i(TAG, "Activity Manager" );

context = ActivityManagerService.main(factoryTest);

Slog.i(TAG, "Telephony Registry" );

ServiceManager.addService("telephony.registry" , new TelephonyRegistry(context));

AttributeCache.init(context);

Slog.i(TAG, "Package Manager" );

pm = PackageManagerService.main(context,

factoryTest != SystemServer.FACTORY_TEST_OFF);

ActivityManagerService.setSystemProcess();

mContentResolver = context.getContentResolver();

// The AccountManager must come before the ContentService

try {

Slog.i(TAG, "Account Manager" );

ServiceManager.addService(Context.ACCOUNT_SERVICE,

new AccountManagerService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Account Manager" , e);

}

Slog.i(TAG, "Content Manager" );

ContentService.main(context,

factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);

Slog.i(TAG, "System Content Providers" );

ActivityManagerService.installSystemProviders();

Slog.i(TAG, "Battery Service" );

battery = new BatteryService(context);

ServiceManager.addService("battery" , battery);

Slog.i(TAG, "Lights Service" );

lights = new LightsService(context);

Slog.i(TAG, "Vibrator Service" );

ServiceManager.addService("vibrator" , new VibratorService(context));

// only initialize the power service after we have started the

// lights service, content providers and the battery service.

power.init(context, lights, ActivityManagerService.getDefault(), battery);

Slog.i(TAG, "Alarm Manager" );

AlarmManagerService alarm = new AlarmManagerService(context);

ServiceManager.addService(Context.ALARM_SERVICE, alarm);

Slog.i(TAG, "Init Watchdog" );

Watchdog.getInstance().init(context, battery, power, alarm,

ActivityManagerService.self());

Slog.i(TAG, "Window Manager" );

wm = WindowManagerService.main(context, power,

factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL);

ServiceManager.addService(Context.WINDOW_SERVICE, wm);

((ActivityManagerService)ServiceManager.getService("activity" ))

.setWindowManager(wm);

// Skip Bluetooth if we have an emulator kernel

// TODO: Use a more reliable check to see if this product should

// support Bluetooth - see bug 988521

if (SystemProperties.get( "ro.kernel.qemu" ).equals( "1" )) {

Slog.i(TAG, "Registering null Bluetooth Service (emulator)" );

ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE, null );

} else if (factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL) {

Slog.i(TAG, "Registering null Bluetooth Service (factory test)" );

ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE, null );

} else {

Slog.i(TAG, "Bluetooth Service" );

bluetooth = new BluetoothService(context);

ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE, bluetooth);

bluetooth.initAfterRegistration();

bluetoothA2dp = new BluetoothA2dpService(context, bluetooth);

ServiceManager.addService(BluetoothA2dpService.BLUETOOTH_A2DP_SERVICE,

bluetoothA2dp);

int bluetoothOn = Settings.Secure.getInt(mContentResolver,

Settings.Secure.BLUETOOTH_ON, 0 );

if (bluetoothOn > 0 ) {

bluetooth.enable();

}

}

} catch (RuntimeException e) {

Slog.e("System" , "Failure starting core service" , e);

}

DevicePolicyManagerService devicePolicy = null ;

StatusBarManagerService statusBar = null ;

InputMethodManagerService imm = null ;

AppWidgetService appWidget = null ;

NotificationManagerService notification = null ;

WallpaperManagerService wallpaper = null ;

LocationManagerService location = null ;

if (factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {

try {

Slog.i(TAG, "Device Policy" );

devicePolicy = new DevicePolicyManagerService(context);

ServiceManager.addService(Context.DEVICE_POLICY_SERVICE, devicePolicy);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting DevicePolicyService" , e);

}

try {

Slog.i(TAG, "Status Bar" );

statusBar = new StatusBarManagerService(context);

ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting StatusBarManagerService" , e);

}

try {

Slog.i(TAG, "Clipboard Service" );

ServiceManager.addService(Context.CLIPBOARD_SERVICE,

new ClipboardService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Clipboard Service" , e);

}

try {

Slog.i(TAG, "Input Method Service" );

imm = new InputMethodManagerService(context, statusBar);

ServiceManager.addService(Context.INPUT_METHOD_SERVICE, imm);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Input Manager Service" , e);

}

try {

Slog.i(TAG, "NetStat Service" );

ServiceManager.addService("netstat" , new NetStatService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting NetStat Service" , e);

}

try {

Slog.i(TAG, "NetworkManagement Service" );

ServiceManager.addService(

Context.NETWORKMANAGEMENT_SERVICE,

NetworkManagementService.create(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting NetworkManagement Service" , e);

}

try {

Slog.i(TAG, "Connectivity Service" );

connectivity = ConnectivityService.getInstance(context);

ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Connectivity Service" , e);

}

try {

Slog.i(TAG, "Throttle Service" );

throttle = new ThrottleService(context);

ServiceManager.addService(

Context.THROTTLE_SERVICE, throttle);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting ThrottleService" , e);

}

try {

Slog.i(TAG, "Accessibility Manager" );

ServiceManager.addService(Context.ACCESSIBILITY_SERVICE,

new AccessibilityManagerService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Accessibility Manager" , e);

}

try {

/*

* NotificationManagerService is dependant on MountService,

* (for media / usb notifications) so we must start MountService first.

*/

Slog.i(TAG, "Mount Service" );

ServiceManager.addService("mount" , new MountService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Mount Service" , e);

}

try {

Slog.i(TAG, "Notification Manager" );

notification = new NotificationManagerService(context, statusBar, lights);

ServiceManager.addService(Context.NOTIFICATION_SERVICE, notification);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Notification Manager" , e);

}

try {

Slog.i(TAG, "Device Storage Monitor" );

ServiceManager.addService(DeviceStorageMonitorService.SERVICE,

new DeviceStorageMonitorService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting DeviceStorageMonitor service" , e);

}

try {

Slog.i(TAG, "Location Manager" );

location = new LocationManagerService(context);

ServiceManager.addService(Context.LOCATION_SERVICE, location);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Location Manager" , e);

}

try {

Slog.i(TAG, "Search Service" );

ServiceManager.addService(Context.SEARCH_SERVICE,

new SearchManagerService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Search Service" , e);

}

if (INCLUDE_DEMO) {

Slog.i(TAG, "Installing demo data..." );

(new DemoThread(context)).start();

}

try {

Slog.i(TAG, "DropBox Service" );

ServiceManager.addService(Context.DROPBOX_SERVICE,

new DropBoxManagerService(context, new File( "/data/system/dropbox" )));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting DropBoxManagerService" , e);

}

try {

Slog.i(TAG, "Wallpaper Service" );

wallpaper = new WallpaperManagerService(context);

ServiceManager.addService(Context.WALLPAPER_SERVICE, wallpaper);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Wallpaper Service" , e);

}

try {

Slog.i(TAG, "Audio Service" );

ServiceManager.addService(Context.AUDIO_SERVICE, new AudioService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Audio Service" , e);

}

try {

Slog.i(TAG, "Headset Observer" );

// Listen for wired headset changes

headset = new HeadsetObserver(context);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting HeadsetObserver" , e);

}

try {

Slog.i(TAG, "Dock Observer" );

// Listen for dock station changes

dock = new DockObserver(context, power);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting DockObserver" , e);

}

try {

Slog.i(TAG, "USB Service" );

// Listen for USB changes

usb = new UsbService(context);

ServiceManager.addService(Context.USB_SERVICE, usb);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting UsbService" , e);

}

try {

Slog.i(TAG, "UI Mode Manager Service" );

// Listen for UI mode changes

uiMode = new UiModeManagerService(context);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting UiModeManagerService" , e);

}

try {

Slog.i(TAG, "Backup Service" );

ServiceManager.addService(Context.BACKUP_SERVICE,

new BackupManagerService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Backup Service" , e);

}

try {

Slog.i(TAG, "AppWidget Service" );

appWidget = new AppWidgetService(context);

ServiceManager.addService(Context.APPWIDGET_SERVICE, appWidget);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting AppWidget Service" , e);

}

try {

Slog.i(TAG, "Recognition Service" );

recognition = new RecognitionManagerService(context);

} catch (Throwable e) {

Slog.e(TAG, "Failure starting Recognition Service" , e);

}

try {

Slog.i(TAG, "DiskStats Service" );

ServiceManager.addService("diskstats" , new DiskStatsService(context));

} catch (Throwable e) {

Slog.e(TAG, "Failure starting DiskStats Service" , e);

}

}

// make sure the ADB_ENABLED setting value matches the secure property value

Settings.Secure.putInt(mContentResolver, Settings.Secure.ADB_ENABLED,

"1" .equals(SystemProperties.get( "persist.service.adb.enable" )) ? 1 : 0);

// register observer to listen for settings changes

mContentResolver.registerContentObserver(Settings.Secure.getUriFor(Settings.Secure.ADB_ENABLED),

false , new AdbSettingsObserver());

// Before things start rolling, be sure we have decided whether

// we are in safe mode.

final boolean safeMode = wm.detectSafeMode();

if (safeMode) {

try {

ActivityManagerNative.getDefault().enterSafeMode();

// Post the safe mode state in the Zygote class

Zygote.systemInSafeMode = true ;

// Disable the JIT for the system_server process

VMRuntime.getRuntime().disableJitCompilation();

} catch (RemoteException e) {

}

} else {

// Enable the JIT for the system_server process

VMRuntime.getRuntime().startJitCompilation();

}

// It is now time to start up the app processes...

if (devicePolicy != null ) {

devicePolicy.systemReady();

}

if (notification != null ) {

notification.systemReady();

}

if (statusBar != null ) {

statusBar.systemReady();

}

wm.systemReady();

power.systemReady();

try {

pm.systemReady();

} catch (RemoteException e) {

}

// These are needed to propagate to the runnable below.

final StatusBarManagerService statusBarF = statusBar;

final BatteryService batteryF = battery;

final ConnectivityService connectivityF = connectivity;

final DockObserver dockF = dock;

final UsbService usbF = usb;

final ThrottleService throttleF = throttle;

final UiModeManagerService uiModeF = uiMode;

final AppWidgetService appWidgetF = appWidget;

final WallpaperManagerService wallpaperF = wallpaper;

final InputMethodManagerService immF = imm;

final RecognitionManagerService recognitionF = recognition;

final LocationManagerService locationF = location;

// 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() {

Slog.i(TAG, "Making services ready" );

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();

}

});

// For debug builds, log event loop stalls to dropbox for analysis.

if (StrictMode.conditionallyEnableDebugLogging()) {

Slog.i(TAG, "Enabled StrictMode for system server main thread." );

}

Looper.loop();

Slog.d(TAG, "System ServerThread is exiting!" );

}

这里启动的每一个进程都作为一个Dalvik线程而存在于SystemServer进程里面。