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
  1. /**
  2. *ThismethodiscalledfromZygotetoinitializethesystem.Thiswillcausethenative
  3. *services(SurfaceFlinger,AudioFlinger,etc..)tobestarted.Afterthatitwillcallback
  4. *upintoinit2()tostarttheAndroidservices.
  5. */
  6. native public static void init1(String[]args);
  8. public static void main(String[]args){
  9. if (System.currentTimeMillis()<EARLIEST_SUPPORTED_TIME){
  10. //Ifadevice'sclockisbefore1970(before0),alotof
  11. //APIscrashdealingwithnegativenumbers,notably
  12. //java.io.File#setLastModified,soinsteadwefakeitand
  13. //hopethattimefromcelltowersorNTPfixesit
  14. //shortly.
  15. Slog.w(TAG,"Systemclockisbefore1970;settingto1970." );
  16. SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
  17. }
  19. if (SamplingProfilerIntegration.isEnabled()){
  20. SamplingProfilerIntegration.start();
  21. timer=new Timer();
  22. timer.schedule(new TimerTask(){
  23. @Override
  24. public void run(){
  25. SamplingProfilerIntegration.writeSnapshot("system_server" );
  26. }
  27. },SNAPSHOT_INTERVAL,SNAPSHOT_INTERVAL);
  28. }
  30. //Thesystemserverhastorunallofthetime,soitneedstobe
  31. //asefficientaspossiblewithitsmemoryusage.
  32. VMRuntime.getRuntime().setTargetHeapUtilization(0 .8f);
  34. System.loadLibrary("android_servers" );
  35. init1(args);
  36. }
  38. public static final void init2(){
  39. Slog.i(TAG,"EnteredtheAndroidsystemserver!" );
  40. Threadthr=new ServerThread();
  41. thr.setName("android.server.ServerThread" );
  42. thr.start();
  43. }

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
  1. extern "C" status_tsystem_init()
  2. {
  3. LOGI("Enteredsystem_init()" );
  5. sp<ProcessState>proc(ProcessState::self());
  7. sp<IServiceManager>sm=defaultServiceManager();
  8. LOGI("ServiceManager:%p\n" ,sm.get());
  10. sp<GrimReaper>grim=new GrimReaper();
  11. sm->asBinder()->linkToDeath(grim,grim.get(),0);
  13. char propBuf[PROPERTY_VALUE_MAX];
  14. property_get("system_init.startsurfaceflinger" ,propBuf, "1" );
  15. if (strcmp(propBuf, "1" )==0){
  16. //StarttheSurfaceFlinger
  17. SurfaceFlinger::instantiate();
  18. }
  20. //Startthesensorservice
  21. SensorService::instantiate();
  23. //Onthesimulator,audioflingeretaldon'tgetstartedthe
  24. //samewayasonthedevice,andweneedtostartthemhere
  25. if (!proc->supportsProcesses()){
  27. //StarttheAudioFlinger
  28. AudioFlinger::instantiate();
  30. //Startthemediaplaybackservice
  31. MediaPlayerService::instantiate();
  33. //Startthecameraservice
  34. CameraService::instantiate();
  36. //Starttheaudiopolicyservice
  37. AudioPolicyService::instantiate();
  38. }
  40. //AndnowstarttheAndroidruntime.Wehavetodothisbit
  41. //ofnastinessbecausetheAndroidruntimeinitializationrequires
  42. //someofthecoresystemservicestoalreadybestarted.
  43. //AllotherserversshouldjuststarttheAndroidruntimeat
  44. //thebeginningoftheirprocesses'smain(),beforecalling
  45. //theinitfunction.
  46. LOGI("Systemserver:startingAndroidruntime.\n" );
  48. AndroidRuntime*runtime=AndroidRuntime::getRuntime();
  50. LOGI("Systemserver:startingAndroidservices.\n" );
  51. runtime->callStatic("com/android/server/SystemServer" , "init2" );
  53. //Ifrunninginourownprocess,justgointothethread
  54. //pool.Otherwise,calltheinitializationfinished
  55. //functoletthisprocesscontinueitsinitilization.
  56. if (proc->supportsProcesses()){
  57. LOGI("Systemserver:enteringthreadpool.\n" );
  58. ProcessState::self()->startThreadPool();
  59. IPCThreadState::self()->joinThreadPool();
  60. LOGI("Systemserver:exitingthreadpool.\n" );
  61. }
  62. return NO_ERROR;
  63. }

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
  1. public void run(){
  2. EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN,
  3. SystemClock.uptimeMillis());
  5. Looper.prepare();
  7. android.os.Process.setThreadPriority(
  8. android.os.Process.THREAD_PRIORITY_FOREGROUND);
  10. BinderInternal.disableBackgroundScheduling(true );
  11. android.os.Process.setCanSelfBackground(false );
  13. //Checkwhetherwefailedtoshutdownlasttimewetried.
  14. {
  15. final StringshutdownAction=SystemProperties.get(
  16. ShutdownThread.SHUTDOWN_ACTION_PROPERTY,"" );
  17. if (shutdownAction!= null &&shutdownAction.length()> 0 ){
  18. boolean reboot=(shutdownAction.charAt( 0 )== '1' );
  20. final Stringreason;
  21. if (shutdownAction.length()> 1 ){
  22. reason=shutdownAction.substring(1 ,shutdownAction.length());
  23. }else {
  24. reason=null ;
  25. }
  27. ShutdownThread.rebootOrShutdown(reboot,reason);
  28. }
  29. }
  31. StringfactoryTestStr=SystemProperties.get("ro.factorytest" );
  32. int factoryTest= "" .equals(factoryTestStr)?SystemServer.FACTORY_TEST_OFF
  33. :Integer.parseInt(factoryTestStr);
  35. LightsServicelights=null ;
  36. PowerManagerServicepower=null ;
  37. BatteryServicebattery=null ;
  38. ConnectivityServiceconnectivity=null ;
  39. IPackageManagerpm=null ;
  40. Contextcontext=null ;
  41. WindowManagerServicewm=null ;
  42. BluetoothServicebluetooth=null ;
  43. BluetoothA2dpServicebluetoothA2dp=null ;
  44. HeadsetObserverheadset=null ;
  45. DockObserverdock=null ;
  46. UsbServiceusb=null ;
  47. UiModeManagerServiceuiMode=null ;
  48. RecognitionManagerServicerecognition=null ;
  49. ThrottleServicethrottle=null ;
  51. //Criticalservices...
  52. try {
  53. Slog.i(TAG,"EntropyService" );
  54. ServiceManager.addService("entropy" , new EntropyService());
  56. Slog.i(TAG,"PowerManager" );
  57. power=new PowerManagerService();
  58. ServiceManager.addService(Context.POWER_SERVICE,power);
  60. Slog.i(TAG,"ActivityManager" );
  61. context=ActivityManagerService.main(factoryTest);
  63. Slog.i(TAG,"TelephonyRegistry" );
  64. ServiceManager.addService("telephony.registry" , new TelephonyRegistry(context));
  66. AttributeCache.init(context);
  68. Slog.i(TAG,"PackageManager" );
  69. pm=PackageManagerService.main(context,
  70. factoryTest!=SystemServer.FACTORY_TEST_OFF);
  72. ActivityManagerService.setSystemProcess();
  74. mContentResolver=context.getContentResolver();
  76. //TheAccountManagermustcomebeforetheContentService
  77. try {
  78. Slog.i(TAG,"AccountManager" );
  79. ServiceManager.addService(Context.ACCOUNT_SERVICE,
  80. new AccountManagerService(context));
  81. }catch (Throwablee){
  82. Slog.e(TAG,"FailurestartingAccountManager" ,e);
  83. }
  85. Slog.i(TAG,"ContentManager" );
  86. ContentService.main(context,
  87. factoryTest==SystemServer.FACTORY_TEST_LOW_LEVEL);
  89. Slog.i(TAG,"SystemContentProviders" );
  90. ActivityManagerService.installSystemProviders();
  92. Slog.i(TAG,"BatteryService" );
  93. battery=new BatteryService(context);
  94. ServiceManager.addService("battery" ,battery);
  96. Slog.i(TAG,"LightsService" );
  97. lights=new LightsService(context);
  99. Slog.i(TAG,"VibratorService" );
  100. ServiceManager.addService("vibrator" , new VibratorService(context));
  102. //onlyinitializethepowerserviceafterwehavestartedthe
  103. //lightsservice,contentprovidersandthebatteryservice.
  104. power.init(context,lights,ActivityManagerService.getDefault(),battery);
  106. Slog.i(TAG,"AlarmManager" );
  107. AlarmManagerServicealarm=new AlarmManagerService(context);
  108. ServiceManager.addService(Context.ALARM_SERVICE,alarm);
  110. Slog.i(TAG,"InitWatchdog" );
  111. Watchdog.getInstance().init(context,battery,power,alarm,
  112. ActivityManagerService.self());
  114. Slog.i(TAG,"WindowManager" );
  115. wm=WindowManagerService.main(context,power,
  116. factoryTest!=SystemServer.FACTORY_TEST_LOW_LEVEL);
  117. ServiceManager.addService(Context.WINDOW_SERVICE,wm);
  119. ((ActivityManagerService)ServiceManager.getService("activity" ))
  120. .setWindowManager(wm);
  122. //SkipBluetoothifwehaveanemulatorkernel
  123. //TODO:Useamorereliablechecktoseeifthisproductshould
  124. //supportBluetooth-seebug988521
  125. if (SystemProperties.get( "ro.kernel.qemu" ).equals( "1" )){
  126. Slog.i(TAG,"RegisteringnullBluetoothService(emulator)" );
  127. ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE,null );
  128. }else if (factoryTest==SystemServer.FACTORY_TEST_LOW_LEVEL){
  129. Slog.i(TAG,"RegisteringnullBluetoothService(factorytest)" );
  130. ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE,null );
  131. }else {
  132. Slog.i(TAG,"BluetoothService" );
  133. bluetooth=new BluetoothService(context);
  134. ServiceManager.addService(BluetoothAdapter.BLUETOOTH_SERVICE,bluetooth);
  135. bluetooth.initAfterRegistration();
  136. bluetoothA2dp=new BluetoothA2dpService(context,bluetooth);
  137. ServiceManager.addService(BluetoothA2dpService.BLUETOOTH_A2DP_SERVICE,
  138. bluetoothA2dp);
  140. int bluetoothOn=Settings.Secure.getInt(mContentResolver,
  141. Settings.Secure.BLUETOOTH_ON,0 );
  142. if (bluetoothOn> 0 ){
  143. bluetooth.enable();
  144. }
  145. }
  147. }catch (RuntimeExceptione){
  148. Slog.e("System" , "Failurestartingcoreservice" ,e);
  149. }
  151. DevicePolicyManagerServicedevicePolicy=null ;
  152. StatusBarManagerServicestatusBar=null ;
  153. InputMethodManagerServiceimm=null ;
  154. AppWidgetServiceappWidget=null ;
  155. NotificationManagerServicenotification=null ;
  156. WallpaperManagerServicewallpaper=null ;
  157. LocationManagerServicelocation=null ;
  159. if (factoryTest!=SystemServer.FACTORY_TEST_LOW_LEVEL){
  160. try {
  161. Slog.i(TAG,"DevicePolicy" );
  162. devicePolicy=new DevicePolicyManagerService(context);
  163. ServiceManager.addService(Context.DEVICE_POLICY_SERVICE,devicePolicy);
  164. }catch (Throwablee){
  165. Slog.e(TAG,"FailurestartingDevicePolicyService" ,e);
  166. }
  168. try {
  169. Slog.i(TAG,"StatusBar" );
  170. statusBar=new StatusBarManagerService(context);
  171. ServiceManager.addService(Context.STATUS_BAR_SERVICE,statusBar);
  172. }catch (Throwablee){
  173. Slog.e(TAG,"FailurestartingStatusBarManagerService" ,e);
  174. }
  176. try {
  177. Slog.i(TAG,"ClipboardService" );
  178. ServiceManager.addService(Context.CLIPBOARD_SERVICE,
  179. new ClipboardService(context));
  180. }catch (Throwablee){
  181. Slog.e(TAG,"FailurestartingClipboardService" ,e);
  182. }
  184. try {
  185. Slog.i(TAG,"InputMethodService" );
  186. imm=new InputMethodManagerService(context,statusBar);
  187. ServiceManager.addService(Context.INPUT_METHOD_SERVICE,imm);
  188. }catch (Throwablee){
  189. Slog.e(TAG,"FailurestartingInputManagerService" ,e);
  190. }
  192. try {
  193. Slog.i(TAG,"NetStatService" );
  194. ServiceManager.addService("netstat" , new NetStatService(context));
  195. }catch (Throwablee){
  196. Slog.e(TAG,"FailurestartingNetStatService" ,e);
  197. }
  199. try {
  200. Slog.i(TAG,"NetworkManagementService" );
  201. ServiceManager.addService(
  202. Context.NETWORKMANAGEMENT_SERVICE,
  203. NetworkManagementService.create(context));
  204. }catch (Throwablee){
  205. Slog.e(TAG,"FailurestartingNetworkManagementService" ,e);
  206. }
  208. try {
  209. Slog.i(TAG,"ConnectivityService" );
  210. connectivity=ConnectivityService.getInstance(context);
  211. ServiceManager.addService(Context.CONNECTIVITY_SERVICE,connectivity);
  212. }catch (Throwablee){
  213. Slog.e(TAG,"FailurestartingConnectivityService" ,e);
  214. }
  216. try {
  217. Slog.i(TAG,"ThrottleService" );
  218. throttle=new ThrottleService(context);
  219. ServiceManager.addService(
  220. Context.THROTTLE_SERVICE,throttle);
  221. }catch (Throwablee){
  222. Slog.e(TAG,"FailurestartingThrottleService" ,e);
  223. }
  225. try {
  226. Slog.i(TAG,"AccessibilityManager" );
  227. ServiceManager.addService(Context.ACCESSIBILITY_SERVICE,
  228. new AccessibilityManagerService(context));
  229. }catch (Throwablee){
  230. Slog.e(TAG,"FailurestartingAccessibilityManager" ,e);
  231. }
  233. try {
  234. /*
  235. *NotificationManagerServiceisdependantonMountService,
  236. *(formedia/usbnotifications)sowemuststartMountServicefirst.
  237. */
  238. Slog.i(TAG,"MountService" );
  239. ServiceManager.addService("mount" , new MountService(context));
  240. }catch (Throwablee){
  241. Slog.e(TAG,"FailurestartingMountService" ,e);
  242. }
  244. try {
  245. Slog.i(TAG,"NotificationManager" );
  246. notification=new NotificationManagerService(context,statusBar,lights);
  247. ServiceManager.addService(Context.NOTIFICATION_SERVICE,notification);
  248. }catch (Throwablee){
  249. Slog.e(TAG,"FailurestartingNotificationManager" ,e);
  250. }
  252. try {
  253. Slog.i(TAG,"DeviceStorageMonitor" );
  254. ServiceManager.addService(DeviceStorageMonitorService.SERVICE,
  255. new DeviceStorageMonitorService(context));
  256. }catch (Throwablee){
  257. Slog.e(TAG,"FailurestartingDeviceStorageMonitorservice" ,e);
  258. }
  260. try {
  261. Slog.i(TAG,"LocationManager" );
  262. location=new LocationManagerService(context);
  263. ServiceManager.addService(Context.LOCATION_SERVICE,location);
  264. }catch (Throwablee){
  265. Slog.e(TAG,"FailurestartingLocationManager" ,e);
  266. }
  268. try {
  269. Slog.i(TAG,"SearchService" );
  270. ServiceManager.addService(Context.SEARCH_SERVICE,
  271. new SearchManagerService(context));
  272. }catch (Throwablee){
  273. Slog.e(TAG,"FailurestartingSearchService" ,e);
  274. }
  276. if (INCLUDE_DEMO){
  277. Slog.i(TAG,"Installingdemodata..." );
  278. (new DemoThread(context)).start();
  279. }
  281. try {
  282. Slog.i(TAG,"DropBoxService" );
  283. ServiceManager.addService(Context.DROPBOX_SERVICE,
  284. new DropBoxManagerService(context, new File( "/data/system/dropbox" )));
  285. }catch (Throwablee){
  286. Slog.e(TAG,"FailurestartingDropBoxManagerService" ,e);
  287. }
  289. try {
  290. Slog.i(TAG,"WallpaperService" );
  291. wallpaper=new WallpaperManagerService(context);
  292. ServiceManager.addService(Context.WALLPAPER_SERVICE,wallpaper);
  293. }catch (Throwablee){
  294. Slog.e(TAG,"FailurestartingWallpaperService" ,e);
  295. }
  297. try {
  298. Slog.i(TAG,"AudioService" );
  299. ServiceManager.addService(Context.AUDIO_SERVICE,new AudioService(context));
  300. }catch (Throwablee){
  301. Slog.e(TAG,"FailurestartingAudioService" ,e);
  302. }
  304. try {
  305. Slog.i(TAG,"HeadsetObserver" );
  306. //Listenforwiredheadsetchanges
  307. headset=new HeadsetObserver(context);
  308. }catch (Throwablee){
  309. Slog.e(TAG,"FailurestartingHeadsetObserver" ,e);
  310. }
  312. try {
  313. Slog.i(TAG,"DockObserver" );
  314. //Listenfordockstationchanges
  315. dock=new DockObserver(context,power);
  316. }catch (Throwablee){
  317. Slog.e(TAG,"FailurestartingDockObserver" ,e);
  318. }
  320. try {
  321. Slog.i(TAG,"USBService" );
  322. //ListenforUSBchanges
  323. usb=new UsbService(context);
  324. ServiceManager.addService(Context.USB_SERVICE,usb);
  325. }catch (Throwablee){
  326. Slog.e(TAG,"FailurestartingUsbService" ,e);
  327. }
  329. try {
  330. Slog.i(TAG,"UIModeManagerService" );
  331. //ListenforUImodechanges
  332. uiMode=new UiModeManagerService(context);
  333. }catch (Throwablee){
  334. Slog.e(TAG,"FailurestartingUiModeManagerService" ,e);
  335. }
  337. try {
  338. Slog.i(TAG,"BackupService" );
  339. ServiceManager.addService(Context.BACKUP_SERVICE,
  340. new BackupManagerService(context));
  341. }catch (Throwablee){
  342. Slog.e(TAG,"FailurestartingBackupService" ,e);
  343. }
  345. try {
  346. Slog.i(TAG,"AppWidgetService" );
  347. appWidget=new AppWidgetService(context);
  348. ServiceManager.addService(Context.APPWIDGET_SERVICE,appWidget);
  349. }catch (Throwablee){
  350. Slog.e(TAG,"FailurestartingAppWidgetService" ,e);
  351. }
  353. try {
  354. Slog.i(TAG,"RecognitionService" );
  355. recognition=new RecognitionManagerService(context);
  356. }catch (Throwablee){
  357. Slog.e(TAG,"FailurestartingRecognitionService" ,e);
  358. }
  360. try {
  361. Slog.i(TAG,"DiskStatsService" );
  362. ServiceManager.addService("diskstats" , new DiskStatsService(context));
  363. }catch (Throwablee){
  364. Slog.e(TAG,"FailurestartingDiskStatsService" ,e);
  365. }
  366. }
  368. //makesuretheADB_ENABLEDsettingvaluematchesthesecurepropertyvalue
  369. Settings.Secure.putInt(mContentResolver,Settings.Secure.ADB_ENABLED,
  370. "1" .equals(SystemProperties.get( "persist.service.adb.enable" ))? 1 : 0 );
  372. //registerobservertolistenforsettingschanges
  373. mContentResolver.registerContentObserver(Settings.Secure.getUriFor(Settings.Secure.ADB_ENABLED),
  374. false , new AdbSettingsObserver());
  376. //Beforethingsstartrolling,besurewehavedecidedwhether
  377. //weareinsafemode.
  378. final boolean safeMode=wm.detectSafeMode();
  379. if (safeMode){
  380. try {
  381. ActivityManagerNative.getDefault().enterSafeMode();
  382. //PostthesafemodestateintheZygoteclass
  383. Zygote.systemInSafeMode=true ;
  384. //DisabletheJITforthesystem_serverprocess
  385. VMRuntime.getRuntime().disableJitCompilation();
  386. }catch (RemoteExceptione){
  387. }
  388. }else {
  389. //EnabletheJITforthesystem_serverprocess
  390. VMRuntime.getRuntime().startJitCompilation();
  391. }
  393. //Itisnowtimetostartuptheappprocesses...
  395. if (devicePolicy!= null ){
  396. devicePolicy.systemReady();
  397. }
  399. if (notification!= null ){
  400. notification.systemReady();
  401. }
  403. if (statusBar!= null ){
  404. statusBar.systemReady();
  405. }
  406. wm.systemReady();
  407. power.systemReady();
  408. try {
  409. pm.systemReady();
  410. }catch (RemoteExceptione){
  411. }
  413. //Theseareneededtopropagatetotherunnablebelow.
  414. final StatusBarManagerServicestatusBarF=statusBar;
  415. final BatteryServicebatteryF=battery;
  416. final ConnectivityServiceconnectivityF=connectivity;
  417. final DockObserverdockF=dock;
  418. final UsbServiceusbF=usb;
  419. final ThrottleServicethrottleF=throttle;
  420. final UiModeManagerServiceuiModeF=uiMode;
  421. final AppWidgetServiceappWidgetF=appWidget;
  422. final WallpaperManagerServicewallpaperF=wallpaper;
  423. final InputMethodManagerServiceimmF=imm;
  424. final RecognitionManagerServicerecognitionF=recognition;
  425. final LocationManagerServicelocationF=location;
  427. //Wenowtelltheactivitymanageritisokaytorunthirdparty
  428. //code.Itwillcallbackintousonceithasgottentothestate
  429. //wherethirdpartycodecanreallyrun(butbeforeithasactually
  430. //startedlaunchingtheinitialapplications),forustocompleteour
  431. //initialization.
  432. ((ActivityManagerService)ActivityManagerNative.getDefault())
  433. .systemReady(new Runnable(){
  434. public void run(){
  435. Slog.i(TAG,"Makingservicesready" );
  437. if (statusBarF!= null )statusBarF.systemReady2();
  438. if (batteryF!= null )batteryF.systemReady();
  439. if (connectivityF!= null )connectivityF.systemReady();
  440. if (dockF!= null )dockF.systemReady();
  441. if (usbF!= null )usbF.systemReady();
  442. if (uiModeF!= null )uiModeF.systemReady();
  443. if (recognitionF!= null )recognitionF.systemReady();
  444. Watchdog.getInstance().start();
  446. //Itisnowokaytoletthevarioussystemservicesstarttheir
  447. //thirdpartycode...
  449. if (appWidgetF!= null )appWidgetF.systemReady(safeMode);
  450. if (wallpaperF!= null )wallpaperF.systemReady();
  451. if (immF!= null )immF.systemReady();
  452. if (locationF!= null )locationF.systemReady();
  453. if (throttleF!= null )throttleF.systemReady();
  454. }
  455. });
  457. //Fordebugbuilds,logeventloopstallstodropboxforanalysis.
  458. if (StrictMode.conditionallyEnableDebugLogging()){
  459. Slog.i(TAG,"EnabledStrictModeforsystemservermainthread." );
  460. }
  462. Looper.loop();
  463. Slog.d(TAG,"SystemServerThreadisexiting!" );
  464. }

这里启动的没一个进程都作为一个Dalvik线程而存在于SystemServer进程里面。





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