Android 启动过程代码跟踪

准备工作：Android源码，SourceInsight

我们知道Android系统在启动时首先会启动Linux系统，引导加载Linux Kernel并启动init进程。Init进程是一个由内核启动的用户级进程，是Android系统的第一个进程。该进程的相关代码在android/system/core/init/init.c。在main函数中，有如下代码：

init_parse_config_file("/init.rc");

action_for_each_trigger("early-init", action_add_queue_tail);

......

/* execute all the boot actions to get us started */
action_for_each_trigger("init", action_add_queue_tail);

/* skip mounting filesystems in charger mode */
if (!is_charger) {
action_for_each_trigger("early-fs", action_add_queue_tail);
action_for_each_trigger("fs", action_add_queue_tail);
action_for_each_trigger("post-fs", action_add_queue_tail);
action_for_each_trigger("post-fs-data", action_add_queue_tail);
}

.......

if (is_charger) {
action_for_each_trigger("charger", action_add_queue_tail);
} else {
action_for_each_trigger("early-boot", action_add_queue_tail);
action_for_each_trigger("boot", action_add_queue_tail);
}

这里会加载init.rc并进行解析，init.rc文件定义了在init进程中需要启动哪些进程服务和执行哪些动作。其详细说明参见android/system/core/init/reademe.txt。init.rc见如下定义：

......
service servicemanager /system/bin/servicemanager
class core
user system
group system
critical
onrestart restart zygote
onrestart restart media
onrestart restart surfaceflinger
onrestart restart drm

service vold /system/bin/vold
class core
socket vold stream 0660 root mount
ioprio be 2

........

service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
class main
socket zygote stream 660 root system
onrestart write /sys/android_power/request_state wake
onrestart write /sys/power/state on
onrestart restart media
onrestart restart netd

service drm /system/bin/drmserver
class main
user drm
group drm system inet drmrpc sdcard_r

service media /system/bin/mediaserver
class main

..........

具体解析过程见android/system/core/init/Init_parser.c。解析所得服务添加到service_list中，动作添加到action_list中。主要代码流程如下：

for (;;) {
switch (next_token(&state)) {
case T_EOF:
state.parse_line(&state, 0, 0);
goto parser_done;
case T_NEWLINE:
state.line++;
if (nargs) {
int kw = lookup_keyword(args[0]);
if (kw_is(kw, SECTION)) {
state.parse_line(&state, 0, 0);
parse_new_section(&state, kw, nargs, args);
} else {
state.parse_line(&state, nargs, args);
}
nargs = 0;
}
break;
case T_TEXT:
if (nargs < INIT_PARSER_MAXARGS) {
args[nargs++] = state.text;
}
break;
}
}

parser_done:
list_for_each(node, &import_list) {
struct import *import = node_to_item(node, struct import, list);
int ret;

INFO("importing '%s'", import->filename);
ret = init_parse_config_file(import->filename);
if (ret)
ERROR("could not import file '%s' from '%s'\n",
import->filename, fn);
}

接下来在main函数中执行动作和启动进程服务：

for(; ;) {
......
execute_one_command();
restart_processes();
......
}

通常init过程需要创建一些系统文件夹并启动USB守护进程、Android
Debug Bridge守护进程、Debug守护进程、ServiceManager进程、Zygote进程等。

由init.rc对ServiceManager的描述service
servicemanager /system/bin/servicemanager可知servicemanager进程从platform\frameworks\base\cmd\servicemanager\Service_manager.cpp启动。在main函数中有如下代码：

int main(int argc, char **argv)
{
struct binder_state *bs;
void *svcmgr = BINDER_SERVICE_MANAGER;

bs = binder_open(128*1024);

if (binder_become_context_manager(bs)) {
ALOGE("cannot become context manager (%s)\n", strerror(errno));
return -1;
}

svcmgr_handle = svcmgr;
binder_loop(bs, svcmgr_handler);
return 0;
}

而在android/framework/base/cmd/servicemanager/Binder.c中

int binder_become_context_manager(struct binder_state *bs)
{
return ioctl(bs->fd, BINDER_SET_CONTEXT_MGR, 0);
}

以上首先调用binder_open()打开Binder设备(/dev/binder)，调用binder_become_context_manager()把当前进程设置为ServiceManager。ServiceManager本身就是一个服务。最后binder_loop()进入循环状态，并设置svcmgr_handler回调函数等待添加、查询、获取服务等请求。

在启动servicemanager的同时，再来启动Zygote，由init.rc对zygote的描述service
zygot /system/bin/app_process可知zygote进程从Android\frameworks\base\cmds\app_process\App_main.cpp启动。这个文件的main（）方法，会调用Android_Runtime.cpp的文件中的start（）方法，这个方法通过JNI机制，来调用ZygoteInit.java孵化器初始文件，这个文件的Main（）函数，将会去调用所有进程。其主要代码如下:

......
while (i < argc) {
const char* arg = argv[i++];
if (!parentDir) {
parentDir = arg;
} else if (strcmp(arg, "--zygote") == 0) {
zygote = true;
niceName = "zygote";
} else if (strcmp(arg, "--start-system-server") == 0) {
startSystemServer = true;
} else if (strcmp(arg, "--application") == 0) {
application = true;
} else if (strncmp(arg, "--nice-name=", 12) == 0) {
niceName = arg + 12;
} else {
className = arg;
break;
}
}
........
if (zygote) {
runtime.start("com.android.internal.os.ZygoteInit",
startSystemServer ? "start-system-server" : "");
} else if (className) {
// Remainder of args get passed to startup class main()
runtime.mClassName = className;
runtime.mArgC = argc - i;
runtime.mArgV = argv + i;
runtime.start("com.android.internal.os.RuntimeInit",
application ? "application" : "tool");
} else {
fprintf(stderr, "Error: no class name or --zygote supplied.\n");
app_usage();
LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
return 10;
}

其中runtime是AppRuntime类型，而AppRuntime继承至AndroidRuntime。我们继续跟踪 runtime.start函数：因在AppRuntime中没有对start的复写，我们到AppRuntime查看start的实现，路劲：android/framework/base/core/init

代码如下：注意runtime.start所传的参数

void AndroidRuntime::start(const char* className, const char* options)
{

if (strcmp(options, "start-system-server") == 0) {

/* start the virtual machine */
JNIEnv* env;
if (startVm(&mJavaVM, &env) != 0) {
return;
}
onVmCreated(env);

...
    /*
     * Start VM.  This thread becomes the main thread of the VM, and will
     * not return until the VM exits.
     */
    char* slashClassName = toSlashClassName(className);
    jclass startClass = env->FindClass(slashClassName);     //com.android.internal.os.ZygoteInit
    if (startClass == NULL) {
        ...
    } else {
        jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
            "([Ljava/lang/String;)V");
        if (startMeth == NULL) {
            ALOGE("JavaVM unable to find main() in '%s'\n", className);
            /* keep going */
        } else {
            env->CallStaticVoidMethod(startClass, startMeth, strArray);
...
        }
    }
    ...
}

即先启动了虚拟机，然后利用JNI调用了zygoteInit。路劲：android/framework/base/core/java/com/android/internal/os在ZygoteInit的main中

public static void main(String argv[]) {
        try {
            ...
            if (argv[1].equals("start-system-server")) {
                startSystemServer();
            } else if (!argv[1].equals("")) {
                throw new RuntimeException(argv[0] + USAGE_STRING);
            }
...
        } catch (MethodAndArgsCaller caller) {
            ...
        }
    }

我们继续跟踪startSystemServer() ， 在startSystemServer()中 ：

  private static boolean startSystemServer()
            throws MethodAndArgsCaller, RuntimeException {
        String args[] = {
            ...
            "--runtime-init",
            "--nice-name=system_server",
            "com.android.server.SystemServer",
        };
       
        try {
            parsedArgs = new ZygoteConnection.Arguments(args);
            ...
            pid = Zygote.forkSystemServer(
                    ...
                    parsedArgs.permittedCapabilities,
                    parsedArgs.effectiveCapabilities);
        } catch (IllegalArgumentException ex) {
            throw new RuntimeException(ex);
        }
...
        return true;
    }

 Zygote包装了Linux的fork。forkSystemServer()调用forkAndSpecialize()，最终穿过虚拟机调用android\dalvik\vm\native\dalvik_system_Zygote.c中Dalvik_dalvik_system_Zygote_forkAndSpecialize()。由dalvik完成fork新的进程。
 main()最后会调用runSelectLoopMode()，进入while循环，由peers创建新的进程。

我们跳转至com.android.server.SystemServer中,目录：android/framework/base/services/java/com/android/server

public static void main(String[] args) {
    	...
        init1(args);
}

在其main()函数中调用了init1(args)这个native函数，利用JNI机制，跟踪至frameworks/base/services/jni/com_android_server_systemService.cpp，然后到
frameworks/base/cmds/system_server/library/system_init.cpp在system_init()函数中有如下代码：

if (strcmp(propBuf, "1") == 0) {
        // Start the SurfaceFlinger
        SurfaceFlinger::instantiate();
    }
    AndroidRuntime* runtime = AndroidRuntime::getRuntime();
  ...
    LOGI("System server: starting Android services./n");
    runtime->callStatic("com/android/server/SystemServer", "init2");
即完成了SurfaceFlinger的实例化，然后利用运行时的callStatic()函数调用了SystemServer的init2()函数.代码如下:

public static final void init2() {
Slog.i(TAG, "Entered the Android system server!");
Thread thr = new ServerThread();
thr.setName("android.server.ServerThread");
thr.start();
}
在这个ServerThread线程中，就可以看到我们熟悉的Android服务了：

@Override
public void run() {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN,
SystemClock.uptimeMillis());

Looper.prepareMainLooper();

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);
final boolean headless = "1".equals(SystemProperties.get("ro.config.headless", "0"));

Installer installer = null;
AccountManagerService accountManager = null;
ContentService contentService = null;
LightsService lights = null;
PowerManagerService power = null;
DynamicPManagerService dpm = null;
DisplayManagerService display = null;
BatteryService battery = null;
VibratorService vibrator = null;
AlarmManagerService alarm = null;
MountService mountService = null;
NetworkManagementService networkManagement = null;
NetworkStatsService networkStats = null;
NetworkPolicyManagerService networkPolicy = null;
ConnectivityService connectivity = null;
WifiP2pService wifiP2p = null;
WifiService wifi = null;
EthernetService ethernet = null;	/*  EthernetService (add by shugeLinux@gmail.com)  */
NsdService serviceDiscovery= null;
IPackageManager pm = null;
Context context = null;
WindowManagerService wm = null;
BluetoothManagerService bluetooth = null;
DockObserver dock = null;
UsbService usb = null;
SerialService serial = null;
TwilightService twilight = null;
UiModeManagerService uiMode = null;
RecognitionManagerService recognition = null;
ThrottleService throttle = null;
NetworkTimeUpdateService networkTimeUpdater = null;
CommonTimeManagementService commonTimeMgmtService = null;
InputManagerService inputManager = null;
TelephonyRegistry telephonyRegistry = null;

// Create a shared handler thread for UI within the system server.
// This thread is used by at least the following components:
// - WindowManagerPolicy
// - KeyguardViewManager
// - DisplayManagerService
HandlerThread uiHandlerThread = new HandlerThread("UI");
uiHandlerThread.start();
Handler uiHandler = new Handler(uiHandlerThread.getLooper());
uiHandler.post(new Runnable() {
@Override
public void run() {
//Looper.myLooper().setMessageLogging(new LogPrinter(
//        Log.VERBOSE, "WindowManagerPolicy", Log.LOG_ID_SYSTEM));
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_FOREGROUND);
android.os.Process.setCanSelfBackground(false);

// For debug builds, log event loop stalls to dropbox for analysis.
if (StrictMode.conditionallyEnableDebugLogging()) {
Slog.i(TAG, "Enabled StrictMode logging for UI Looper");
}
}
});

// Create a handler thread just for the window manager to enjoy.
HandlerThread wmHandlerThread = new HandlerThread("WindowManager");
wmHandlerThread.start();
Handler wmHandler = new Handler(wmHandlerThread.getLooper());
wmHandler.post(new Runnable() {
@Override
public void run() {
//Looper.myLooper().setMessageLogging(new LogPrinter(
//        android.util.Log.DEBUG, TAG, android.util.Log.LOG_ID_SYSTEM));
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_DISPLAY);
android.os.Process.setCanSelfBackground(false);

// For debug builds, log event loop stalls to dropbox for analysis.
if (StrictMode.conditionallyEnableDebugLogging()) {
Slog.i(TAG, "Enabled StrictMode logging for WM Looper");
}
}
});

// Critical services...
boolean onlyCore = false;
try {
// Wait for installd to finished starting up so that it has a chance to
// create critical directories such as /data/user with the appropriate
// permissions.  We need this to complete before we initialize other services.
Slog.i(TAG, "Waiting for installd to be ready.");
installer = new Installer();
installer.ping();

Slog.i(TAG, "Entropy Mixer");
ServiceManager.addService("entropy", new EntropyMixer());

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, "Display Manager");
display = new DisplayManagerService(context, wmHandler, uiHandler);
ServiceManager.addService(Context.DISPLAY_SERVICE, display, true);

Slog.i(TAG, "Telephony Registry");
telephonyRegistry = new TelephonyRegistry(context);
ServiceManager.addService("telephony.registry", telephonyRegistry);

Slog.i(TAG, "Scheduling Policy");
ServiceManager.addService(Context.SCHEDULING_POLICY_SERVICE,
new SchedulingPolicyService());

AttributeCache.init(context);

if (!display.waitForDefaultDisplay()) {
reportWtf("Timeout waiting for default display to be initialized.",
new Throwable());
}

Slog.i(TAG, "Package Manager");
// Only run "core" apps if we're encrypting the device.
String cryptState = SystemProperties.get("vold.decrypt");
if (ENCRYPTING_STATE.equals(cryptState)) {
Slog.w(TAG, "Detected encryption in progress - only parsing core apps");
onlyCore = true;
} else if (ENCRYPTED_STATE.equals(cryptState)) {
Slog.w(TAG, "Device encrypted - only parsing core apps");
onlyCore = true;
}

pm = PackageManagerService.main(context, installer,
factoryTest != SystemServer.FACTORY_TEST_OFF,
onlyCore);
boolean firstBoot = false;
try {
firstBoot = pm.isFirstBoot();
} catch (RemoteException e) {
}

ActivityManagerService.setSystemProcess();

Slog.i(TAG, "User Service");
ServiceManager.addService(Context.USER_SERVICE,
UserManagerService.getInstance());

mContentResolver = context.getContentResolver();

// The AccountManager must come before the ContentService
try {
Slog.i(TAG, "Account Manager");
accountManager = new AccountManagerService(context);
ServiceManager.addService(Context.ACCOUNT_SERVICE, accountManager);
} catch (Throwable e) {
Slog.e(TAG, "Failure starting Account Manager", e);
}

Slog.i(TAG, "Content Manager");
contentService = ContentService.main(context,
factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);

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

Slog.i(TAG, "Lights Service");
lights = new LightsService(context);

Slog.i(TAG, "Battery Service");
battery = new BatteryService(context, lights);
ServiceManager.addService("battery", battery);

Slog.i(TAG, "DynamicPManager");
dpm = new DynamicPManagerService(context);
ServiceManager.addService(DynamicPManager.DPM_SERVICE, dpm);

Slog.i(TAG, "Vibrator Service");
vibrator = new VibratorService(context);
ServiceManager.addService("vibrator", vibrator);

// only initialize the power service after we have started the
// lights service, content providers and the battery service.
power.init(context, lights, ActivityManagerService.self(), battery,
BatteryStatsService.getService(), display);

Slog.i(TAG, "Alarm Manager");
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, "Input Manager");
inputManager = new InputManagerService(context, wmHandler);

Slog.i(TAG, "Window Manager");
wm = WindowManagerService.main(context, power, display, inputManager,
uiHandler, wmHandler,
factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL,
!firstBoot, onlyCore);
ServiceManager.addService(Context.WINDOW_SERVICE, wm);
ServiceManager.addService(Context.INPUT_SERVICE, inputManager);

if(SystemProperties.get("ro.display.switch").equals("1"))
{
Slog.i(TAG, "Display Manager");
DisplayManagerServiceAw display_aw = new DisplayManagerServiceAw(context,power);
ServiceManager.addService(Context.DISPLAY_SERVICE_AW, display_aw);
}

if(SystemProperties.get("ro.wifidisplay.switch").equals("1"))
{
Slog.i(TAG, "Display Manager");
WifiDisplayManagerService wifidisplay = new WifiDisplayManagerService(context,power);
ServiceManager.addService(Context.WIFIDISPLAY_SERVICE, wifidisplay);
}

ActivityManagerService.self().setWindowManager(wm);

inputManager.setWindowManagerCallbacks(wm.getInputMonitor());
inputManager.start();

display.setWindowManager(wm);
display.setInputManager(inputManager);

// 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, "No Bluetooh Service (emulator)");
} else if (factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL) {
Slog.i(TAG, "No Bluetooth Service (factory test)");
} else {
Slog.i(TAG, "Bluetooth Manager Service");
bluetooth = new BluetoothManagerService(context);
ServiceManager.addService(BluetoothAdapter.BLUETOOTH_MANAGER_SERVICE, bluetooth);
}

} catch (RuntimeException e) {
Slog.e("System", "******************************************");
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;
CountryDetectorService countryDetector = null;
TextServicesManagerService tsms = null;
LockSettingsService lockSettings = null;
DreamManagerService dreamy = null;

// Bring up services needed for UI.
if (factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {
try {
Slog.i(TAG, "Input Method Service");
imm = new InputMethodManagerService(context, wm);
ServiceManager.addService(Context.INPUT_METHOD_SERVICE, imm);
} catch (Throwable e) {
reportWtf("starting Input Manager Service", e);
}

try {
Slog.i(TAG, "Accessibility Manager");
ServiceManager.addService(Context.ACCESSIBILITY_SERVICE,
new AccessibilityManagerService(context));
} catch (Throwable e) {
reportWtf("starting Accessibility Manager", e);
}
}

try {
wm.displayReady();
} catch (Throwable e) {
reportWtf("making display ready", e);
}

try {
pm.performBootDexOpt();
} catch (Throwable e) {
reportWtf("performing boot dexopt", e);
}

try {
ActivityManagerNative.getDefault().showBootMessage(
context.getResources().getText(
com.android.internal.R.string.android_upgrading_starting_apps),
false);
} catch (RemoteException e) {
}

if (factoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {
if (!"0".equals(SystemProperties.get("system_init.startmountservice"))) {
try {
/*
* NotificationManagerService is dependant on MountService,
* (for media / usb notifications) so we must start MountService first.
*/
Slog.i(TAG, "Mount Service");
mountService = new MountService(context);
ServiceManager.addService("mount", mountService);
} catch (Throwable e) {
reportWtf("starting Mount Service", e);
}
}

try {
Slog.i(TAG,  "LockSettingsService");
lockSettings = new LockSettingsService(context);
ServiceManager.addService("lock_settings", lockSettings);
} catch (Throwable e) {
reportWtf("starting LockSettingsService service", e);
}

try {
Slog.i(TAG, "Device Policy");
devicePolicy = new DevicePolicyManagerService(context);
ServiceManager.addService(Context.DEVICE_POLICY_SERVICE, devicePolicy);
} catch (Throwable e) {
reportWtf("starting DevicePolicyService", e);
}

try {
Slog.i(TAG, "Status Bar");
statusBar = new StatusBarManagerService(context, wm);
ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar);
} catch (Throwable e) {
reportWtf("starting StatusBarManagerService", e);
}

try {
Slog.i(TAG, "Clipboard Service");
ServiceManager.addService(Context.CLIPBOARD_SERVICE,
new ClipboardService(context));
} catch (Throwable e) {
reportWtf("starting Clipboard Service", e);
}

try {
Slog.i(TAG, "NetworkManagement Service");
networkManagement = NetworkManagementService.create(context);
ServiceManager.addService(Context.NETWORKMANAGEMENT_SERVICE, networkManagement);
} catch (Throwable e) {
reportWtf("starting NetworkManagement Service", e);
}

try {
Slog.i(TAG, "Text Service Manager Service");
tsms = new TextServicesManagerService(context);
ServiceManager.addService(Context.TEXT_SERVICES_MANAGER_SERVICE, tsms);
} catch (Throwable e) {
reportWtf("starting Text Service Manager Service", e);
}

try {
Slog.i(TAG, "NetworkStats Service");
networkStats = new NetworkStatsService(context, networkManagement, alarm);
ServiceManager.addService(Context.NETWORK_STATS_SERVICE, networkStats);
} catch (Throwable e) {
reportWtf("starting NetworkStats Service", e);
}

try {
Slog.i(TAG, "NetworkPolicy Service");
networkPolicy = new NetworkPolicyManagerService(
context, ActivityManagerService.self(), power,
networkStats, networkManagement);
ServiceManager.addService(Context.NETWORK_POLICY_SERVICE, networkPolicy);
} catch (Throwable e) {
reportWtf("starting NetworkPolicy Service", e);
}

try {
Slog.i(TAG, "Wi-Fi P2pService");
wifiP2p = new WifiP2pService(context);
ServiceManager.addService(Context.WIFI_P2P_SERVICE, wifiP2p);
} catch (Throwable e) {
reportWtf("starting Wi-Fi P2pService", e);
}

/* Begin (add by shugeLinux@gmail.com) */
try {
Slog.i(TAG, "Ethernet Service");
ethernet = new EthernetService(context);
ServiceManager.addService(Context.ETHERNET_SERVICE, ethernet);
} catch (Throwable e) {
reportWtf("starting Ethernet Service", e);
}
/* End (add by shugeLinux@gmail.com) */

try {
Slog.i(TAG, "Wi-Fi Service");
wifi = new WifiService(context);
ServiceManager.addService(Context.WIFI_SERVICE, wifi);
} catch (Throwable e) {
reportWtf("starting Wi-Fi Service", e);
}

try {
Slog.i(TAG, "Connectivity Service");
connectivity = new ConnectivityService(
context, networkManagement, networkStats, networkPolicy);
ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);
networkStats.bindConnectivityManager(connectivity);
networkPolicy.bindConnectivityManager(connectivity);
wifi.checkAndStartWifi();
wifiP2p.connectivityServiceReady();
} catch (Throwable e) {
reportWtf("starting Connectivity Service", e);
}

try {
Slog.i(TAG, "Network Service Discovery Service");
serviceDiscovery = NsdService.create(context);
ServiceManager.addService(
Context.NSD_SERVICE, serviceDiscovery);
} catch (Throwable e) {
reportWtf("starting Service Discovery Service", e);
}

try {
Slog.i(TAG, "Throttle Service");
throttle = new ThrottleService(context);
ServiceManager.addService(
Context.THROTTLE_SERVICE, throttle);
} catch (Throwable e) {
reportWtf("starting ThrottleService", e);
}

try {
Slog.i(TAG, "UpdateLock Service");
ServiceManager.addService(Context.UPDATE_LOCK_SERVICE,
new UpdateLockService(context));
} catch (Throwable e) {
reportWtf("starting UpdateLockService", e);
}

/*
* MountService has a few dependencies: Notification Manager and
* AppWidget Provider. Make sure MountService is completely started
* first before continuing.
*/
if (mountService != null) {
mountService.waitForAsecScan();
}

try {
if (accountManager != null)
accountManager.systemReady();
} catch (Throwable e) {
reportWtf("making Account Manager Service ready", e);
}

try {
if (contentService != null)
contentService.systemReady();
} catch (Throwable e) {
reportWtf("making Content Service ready", e);
}

try {
Slog.i(TAG, "Notification Manager");
notification = new NotificationManagerService(context, statusBar, lights);
ServiceManager.addService(Context.NOTIFICATION_SERVICE, notification);
networkPolicy.bindNotificationManager(notification);
} catch (Throwable e) {
reportWtf("starting Notification Manager", e);
}

try {
Slog.i(TAG, "Device Storage Monitor");
ServiceManager.addService(DeviceStorageMonitorService.SERVICE,
new DeviceStorageMonitorService(context));
} catch (Throwable e) {
reportWtf("starting DeviceStorageMonitor service", e);
}

try {
Slog.i(TAG, "Location Manager");
location = new LocationManagerService(context);
ServiceManager.addService(Context.LOCATION_SERVICE, location);
} catch (Throwable e) {
reportWtf("starting Location Manager", e);
}

try {
Slog.i(TAG, "Country Detector");
countryDetector = new CountryDetectorService(context);
ServiceManager.addService(Context.COUNTRY_DETECTOR, countryDetector);
} catch (Throwable e) {
reportWtf("starting Country Detector", e);
}

try {
Slog.i(TAG, "Search Service");
ServiceManager.addService(Context.SEARCH_SERVICE,
new SearchManagerService(context));
} catch (Throwable e) {
reportWtf("starting Search Service", e);
}

try {
Slog.i(TAG, "DropBox Service");
ServiceManager.addService(Context.DROPBOX_SERVICE,
new DropBoxManagerService(context, new File("/data/system/dropbox")));
} catch (Throwable e) {
reportWtf("starting DropBoxManagerService", e);
}

if (context.getResources().getBoolean(
com.android.internal.R.bool.config_enableWallpaperService)) {
try {
Slog.i(TAG, "Wallpaper Service");
if (!headless) {
wallpaper = new WallpaperManagerService(context);
ServiceManager.addService(Context.WALLPAPER_SERVICE, wallpaper);
}
} catch (Throwable e) {
reportWtf("starting Wallpaper Service", e);
}
}

if (!"0".equals(SystemProperties.get("system_init.startaudioservice"))) {
try {
Slog.i(TAG, "Audio Service");
ServiceManager.addService(Context.AUDIO_SERVICE, new AudioService(context));
} catch (Throwable e) {
reportWtf("starting Audio Service", e);
}
}

try {
Slog.i(TAG, "Dock Observer");
// Listen for dock station changes
dock = new DockObserver(context);
} catch (Throwable e) {
reportWtf("starting DockObserver", e);
}

try {
Slog.i(TAG, "Wired Accessory Manager");
// Listen for wired headset changes
inputManager.setWiredAccessoryCallbacks(
new WiredAccessoryManager(context, inputManager));
} catch (Throwable e) {
reportWtf("starting WiredAccessoryManager", e);
}

try {
Slog.i(TAG, "USB Service");
// Manage USB host and device support
usb = new UsbService(context);
ServiceManager.addService(Context.USB_SERVICE, usb);
} catch (Throwable e) {
reportWtf("starting UsbService", e);
}

try {
Slog.i(TAG, "Serial Service");
// Serial port support
serial = new SerialService(context);
ServiceManager.addService(Context.SERIAL_SERVICE, serial);
} catch (Throwable e) {
Slog.e(TAG, "Failure starting SerialService", e);
}

try {
Slog.i(TAG, "Twilight Service");
twilight = new TwilightService(context);
} catch (Throwable e) {
reportWtf("starting TwilightService", e);
}

try {
Slog.i(TAG, "UI Mode Manager Service");
// Listen for UI mode changes
uiMode = new UiModeManagerService(context, twilight);
} catch (Throwable e) {
reportWtf("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) {
reportWtf("starting AppWidget Service", e);
}

try {
Slog.i(TAG, "Recognition Service");
recognition = new RecognitionManagerService(context);
} catch (Throwable e) {
reportWtf("starting Recognition Service", e);
}

try {
Slog.i(TAG, "DiskStats Service");
ServiceManager.addService("diskstats", new DiskStatsService(context));
} catch (Throwable e) {
reportWtf("starting DiskStats Service", e);
}

try {
// need to add this service even if SamplingProfilerIntegration.isEnabled()
// is false, because it is this service that detects system property change and
// turns on SamplingProfilerIntegration. Plus, when sampling profiler doesn't work,
// there is little overhead for running this service.
Slog.i(TAG, "SamplingProfiler Service");
ServiceManager.addService("samplingprofiler",
new SamplingProfilerService(context));
} catch (Throwable e) {
reportWtf("starting SamplingProfiler Service", e);
}

try {
Slog.i(TAG, "NetworkTimeUpdateService");
networkTimeUpdater = new NetworkTimeUpdateService(context);
} catch (Throwable e) {
reportWtf("starting NetworkTimeUpdate service", e);
}

try {
Slog.i(TAG, "CommonTimeManagementService");
commonTimeMgmtService = new CommonTimeManagementService(context);
ServiceManager.addService("commontime_management", commonTimeMgmtService);
} catch (Throwable e) {
reportWtf("starting CommonTimeManagementService service", e);
}

try {
Slog.i(TAG, "CertBlacklister");
CertBlacklister blacklister = new CertBlacklister(context);
} catch (Throwable e) {
reportWtf("starting CertBlacklister", e);
}

if (context.getResources().getBoolean(
com.android.internal.R.bool.config_dreamsSupported)) {
try {
Slog.i(TAG, "Dreams Service");
// Dreams (interactive idle-time views, a/k/a screen savers)
dreamy = new DreamManagerService(context, wmHandler);
ServiceManager.addService(DreamService.DREAM_SERVICE, dreamy);
} catch (Throwable e) {
reportWtf("starting DreamManagerService", e);
}
}
}

// Before things start rolling, be sure we have decided whether
// we are in safe mode.
final boolean safeMode = wm.detectSafeMode();
if (safeMode) {
ActivityManagerService.self().enterSafeMode();
// Post the safe mode state in the Zygote class
Zygote.systemInSafeMode = true;
// Disable the JIT for the system_server process
VMRuntime.getRuntime().disableJitCompilation();
} else {
// Enable the JIT for the system_server process
VMRuntime.getRuntime().startJitCompilation();
}

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

try {
vibrator.systemReady();
} catch (Throwable e) {
reportWtf("making Vibrator Service ready", e);
}

try {
lockSettings.systemReady();
} catch (Throwable e) {
reportWtf("making Lock Settings Service ready", e);
}

if (devicePolicy != null) {
try {
devicePolicy.systemReady();
} catch (Throwable e) {
reportWtf("making Device Policy Service ready", e);
}
}

if (notification != null) {
try {
notification.systemReady();
} catch (Throwable e) {
reportWtf("making Notification Service ready", e);
}
}

try {
wm.systemReady();
} catch (Throwable e) {
reportWtf("making Window Manager Service ready", e);
}

if (safeMode) {
ActivityManagerService.self().showSafeModeOverlay();
}

// Update the configuration for this context by hand, because we're going
// to start using it before the config change done in wm.systemReady() will
// propagate to it.
Configuration config = wm.computeNewConfiguration();
DisplayMetrics metrics = new DisplayMetrics();
WindowManager w = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
w.getDefaultDisplay().getMetrics(metrics);
context.getResources().updateConfiguration(config, metrics);

try {
power.systemReady(twilight, dreamy);
} catch (Throwable e) {
reportWtf("making Power Manager Service ready", e);
}

try {
pm.systemReady();
} catch (Throwable e) {
reportWtf("making Package Manager Service ready", e);
}

try {
display.systemReady(safeMode, onlyCore);
} catch (Throwable e) {
reportWtf("making Display Manager Service ready", e);
}

// These are needed to propagate to the runnable below.
final Context contextF = context;
final MountService mountServiceF = mountService;
final BatteryService batteryF = battery;
final NetworkManagementService networkManagementF = networkManagement;
final NetworkStatsService networkStatsF = networkStats;
final NetworkPolicyManagerService networkPolicyF = networkPolicy;
final ConnectivityService connectivityF = connectivity;
final DockObserver dockF = dock;
final UsbService usbF = usb;
final ThrottleService throttleF = throttle;
final TwilightService twilightF = twilight;
final UiModeManagerService uiModeF = uiMode;
final AppWidgetService appWidgetF = appWidget;
final WallpaperManagerService wallpaperF = wallpaper;
final InputMethodManagerService immF = imm;
final RecognitionManagerService recognitionF = recognition;
final LocationManagerService locationF = location;
final CountryDetectorService countryDetectorF = countryDetector;
final NetworkTimeUpdateService networkTimeUpdaterF = networkTimeUpdater;
final CommonTimeManagementService commonTimeMgmtServiceF = commonTimeMgmtService;
final TextServicesManagerService textServiceManagerServiceF = tsms;
final StatusBarManagerService statusBarF = statusBar;
final DreamManagerService dreamyF = dreamy;
final InputManagerService inputManagerF = inputManager;
final TelephonyRegistry telephonyRegistryF = telephonyRegistry;

// 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.self().systemReady(new Runnable() {
public void run() {
Slog.i(TAG, "Making services ready");

if (!headless) startSystemUi(contextF);
try {
if (mountServiceF != null) mountServiceF.systemReady();
} catch (Throwable e) {
reportWtf("making Mount Service ready", e);
}
try {
if (batteryF != null) batteryF.systemReady();
} catch (Throwable e) {
reportWtf("making Battery Service ready", e);
}
try {
if (networkManagementF != null) networkManagementF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Managment Service ready", e);
}
try {
if (networkStatsF != null) networkStatsF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Stats Service ready", e);
}
try {
if (networkPolicyF != null) networkPolicyF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Policy Service ready", e);
}
try {
if (connectivityF != null) connectivityF.systemReady();
} catch (Throwable e) {
reportWtf("making Connectivity Service ready", e);
}
try {
if (dockF != null) dockF.systemReady();
} catch (Throwable e) {
reportWtf("making Dock Service ready", e);
}
try {
if (usbF != null) usbF.systemReady();
} catch (Throwable e) {
reportWtf("making USB Service ready", e);
}
try {
if (twilightF != null) twilightF.systemReady();
} catch (Throwable e) {
reportWtf("makin Twilight Service ready", e);
}
try {
if (uiModeF != null) uiModeF.systemReady();
} catch (Throwable e) {
reportWtf("making UI Mode Service ready", e);
}
try {
if (recognitionF != null) recognitionF.systemReady();
} catch (Throwable e) {
reportWtf("making Recognition Service ready", e);
}
Watchdog.getInstance().start();

// It is now okay to let the various system services start their
// third party code...

try {
if (appWidgetF != null) appWidgetF.systemReady(safeMode);
} catch (Throwable e) {
reportWtf("making App Widget Service ready", e);
}
try {
if (wallpaperF != null) wallpaperF.systemReady();
} catch (Throwable e) {
reportWtf("making Wallpaper Service ready", e);
}
try {
if (immF != null) immF.systemReady(statusBarF);
} catch (Throwable e) {
reportWtf("making Input Method Service ready", e);
}
try {
if (locationF != null) locationF.systemReady();
} catch (Throwable e) {
reportWtf("making Location Service ready", e);
}
try {
if (countryDetectorF != null) countryDetectorF.systemReady();
} catch (Throwable e) {
reportWtf("making Country Detector Service ready", e);
}
try {
if (throttleF != null) throttleF.systemReady();
} catch (Throwable e) {
reportWtf("making Throttle Service ready", e);
}
try {
if (networkTimeUpdaterF != null) networkTimeUpdaterF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Time Service ready", e);
}
try {
if (commonTimeMgmtServiceF != null) commonTimeMgmtServiceF.systemReady();
} catch (Throwable e) {
reportWtf("making Common time management service ready", e);
}
try {
if (textServiceManagerServiceF != null) textServiceManagerServiceF.systemReady();
} catch (Throwable e) {
reportWtf("making Text Services Manager Service ready", e);
}
try {
if (dreamyF != null) dreamyF.systemReady();
} catch (Throwable e) {
reportWtf("making DreamManagerService ready", e);
}
try {
// TODO(BT) Pass parameter to input manager
if (inputManagerF != null) inputManagerF.systemReady();
} catch (Throwable e) {
reportWtf("making InputManagerService ready", e);
}
try {
if (telephonyRegistryF != null) telephonyRegistryF.systemReady();
} catch (Throwable e) {
reportWtf("making TelephonyRegistry ready", e);
}
}
});

// 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!");
}

最后，调用各服务的systemReady()函数通知系统就绪,至此，系统的启动过程结束.