SystemServer 進(jìn)程
- 1.1 SystemServer進(jìn)程是由Zygote進(jìn)程fork 出來的精盅。上篇介紹了fork過程
- 1.2 SystemServer進(jìn)程 是用來啟動(dòng)各種系統(tǒng)服務(wù)的進(jìn)程淀散，例如ActivityManagerService,WindowManagerService,PowerManagerService钥勋，PackageManagerService等等初橘，當(dāng)應(yīng)用需要系統(tǒng)服務(wù)也是通過SystemServer進(jìn)程通訊獲取服務(wù)對(duì)象進(jìn)行交互勾习。
SystemServer 調(diào)用
- 初始化
/**
* The main entry point from zygote.
*/
public static void main(String[] args) {
new SystemServer().run();
}
private void run() {
// 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.
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
// If the system has "persist.sys.language" and friends set, replace them with
// "persist.sys.locale". Note that the default locale at this point is calculated
// using the "-Duser.locale" command line flag. That flag is usually populated by
// AndroidRuntime using the same set of system properties, but only the system_server
// and system apps are allowed to set them.
//
// NOTE: Most changes made here will need an equivalent change to
// core/jni/AndroidRuntime.cpp
if (!SystemProperties.get("persist.sys.language").isEmpty()) {
final String languageTag = Locale.getDefault().toLanguageTag();
SystemProperties.set("persist.sys.locale", languageTag);
SystemProperties.set("persist.sys.language", "");
SystemProperties.set("persist.sys.country", "");
SystemProperties.set("persist.sys.localevar", "");
}
// Here we go!
Slog.i(TAG, "Entered the Android system server!");
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, SystemClock.uptimeMillis());
// In case the runtime switched since last boot (such as when
// the old runtime was removed in an OTA), set the system
// property so that it is in sync. We can't do this in
// libnativehelper's JniInvocation::Init code where we already
// had to fallback to a different runtime because it is
// running as root and we need to be the system user to set
// the property. http://b/11463182
SystemProperties.set("persist.sys.dalvik.vm.lib.2", VMRuntime.getRuntime().vmLibrary());
// Enable the sampling profiler.
if (SamplingProfilerIntegration.isEnabled()) {
SamplingProfilerIntegration.start();
mProfilerSnapshotTimer = new Timer();
mProfilerSnapshotTimer.schedule(new TimerTask() {
@Override
public void run() {
SamplingProfilerIntegration.writeSnapshot("system_server", null);
}
}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);
}
// Mmmmmm... more memory!
VMRuntime.getRuntime().clearGrowthLimit();
// 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);
// Some devices rely on runtime fingerprint generation, so make sure
// we've defined it before booting further.
Build.ensureFingerprintProperty();
// Within the system server, it is an error to access Environment paths without
// explicitly specifying a user.
Environment.setUserRequired(true);
// Ensure binder calls into the system always run at foreground priority.
BinderInternal.disableBackgroundScheduling(true);
// Prepare the main looper thread (this thread).
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_FOREGROUND);
android.os.Process.setCanSelfBackground(false);
Looper.prepareMainLooper();
// Initialize native services.
System.loadLibrary("android_servers");
// Check whether we failed to shut down last time we tried.
// This call may not return.
performPendingShutdown();
// Initialize the system context.
createSystemContext();
// Create the system service manager.
mSystemServiceManager = new SystemServiceManager(mSystemContext);
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
// Start services.
try {
startBootstrapServices();
startCoreServices();
startOtherServices();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
}
// For debug builds, log event loop stalls to dropbox for analysis.
if (StrictMode.conditionallyEnableDebugLogging()) {
Slog.i(TAG, "Enabled StrictMode for system server main thread.");
}
// Loop forever.
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
- 1.1 初始化系統(tǒng)時(shí)間
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
- 1.2 設(shè)置語言轧坎，位置股耽，國家,地區(qū)（只有系統(tǒng)app和系統(tǒng)服務(wù)可修改）
if (!SystemProperties.get("persist.sys.language").isEmpty()) {
final String languageTag = Locale.getDefault().toLanguageTag();
SystemProperties.set("persist.sys.locale", languageTag);
SystemProperties.set("persist.sys.language", "");
SystemProperties.set("persist.sys.country", "");
SystemProperties.set("persist.sys.localevar", "");
}
- 1.3 接下來無關(guān)緊要蹄咖，設(shè)置虛擬機(jī)運(yùn)行內(nèi)存褐健，加載運(yùn)行庫，初始化SystemServer進(jìn)程異步消息Looper
Looper.prepareMainLooper();
Looper.loop();
- 2 創(chuàng)建SystemServer系統(tǒng)Context
private void createSystemContext() {
ActivityThread activityThread = ActivityThread.systemMain();
mSystemContext = activityThread.getSystemContext();
mSystemContext.setTheme(android.R.style.Theme_DeviceDefault_Light_DarkActionBar);
}
- 3 創(chuàng)建SystemServiceManager，SystemServiceManager是用來初始化各種系統(tǒng)服務(wù)的蚜迅。創(chuàng)建之后舵匾，并存儲(chǔ)起來。
mSystemServiceManager = new SystemServiceManager(mSystemContext);
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
- 4 啟動(dòng)服務(wù)
startBootstrapServices 啟動(dòng)系統(tǒng)Boot級(jí)服務(wù)
startCoreServices 啟動(dòng)系統(tǒng)核心服務(wù)
startOtherServices 啟動(dòng)系統(tǒng)其他服務(wù)
// Start services.
try {
startBootstrapServices();
startCoreServices();
startOtherServices();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
}
- 4.1 startBootstrapServices
先上源碼
private void startBootstrapServices() {
// Wait for installd to finish 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.
Installer installer = mSystemServiceManager.startService(Installer.class);
// Activity manager runs the show.
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
mActivityManagerService.setInstaller(installer);
// Power manager needs to be started early because other services need it.
// Native daemons may be watching for it to be registered so it must be ready
// to handle incoming binder calls immediately (including being able to verify
// the permissions for those calls).
mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);
// Now that the power manager has been started, let the activity manager
// initialize power management features.
mActivityManagerService.initPowerManagement();
// Manages LEDs and display backlight so we need it to bring up the display.
mSystemServiceManager.startService(LightsService.class);
// Display manager is needed to provide display metrics before package manager
// starts up.
mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);
// We need the default display before we can initialize the package manager.
mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);
// 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");
mOnlyCore = true;
} else if (ENCRYPTED_STATE.equals(cryptState)) {
Slog.w(TAG, "Device encrypted - only parsing core apps");
mOnlyCore = true;
}
// Start the package manager.
Slog.i(TAG, "Package Manager");
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
mFirstBoot = mPackageManagerService.isFirstBoot();
mPackageManager = mSystemContext.getPackageManager();
Slog.i(TAG, "User Service");
ServiceManager.addService(Context.USER_SERVICE, UserManagerService.getInstance());
// Initialize attribute cache used to cache resources from packages.
AttributeCache.init(mSystemContext);
// Set up the Application instance for the system process and get started.
mActivityManagerService.setSystemProcess();
// The sensor service needs access to package manager service, app ops
// service, and permissions service, therefore we start it after them.
startSensorService();
}
- 4.1.1 首先startService
Installer installer = mSystemServiceManager.startService(Installer.class);
查看SystemServiceManager
public <T extends SystemService> T startService(Class<T> serviceClass) {
final String name = serviceClass.getName();
Slog.i(TAG, "Starting " + name);
// Create the service.
if (!SystemService.class.isAssignableFrom(serviceClass)) {
throw new RuntimeException("Failed to create " + name
+ ": service must extend " + SystemService.class.getName());
}
final T service;
try {
Constructor<T> constructor = serviceClass.getConstructor(Context.class);
service = constructor.newInstance(mContext);
} catch (InstantiationException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service could not be instantiated", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (NoSuchMethodException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (InvocationTargetException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service constructor threw an exception", ex);
}
// Register it.
mServices.add(service);
// Start it.
try {
service.onStart();
} catch (RuntimeException ex) {
throw new RuntimeException("Failed to start service " + name
+ ": onStart threw an exception", ex);
}
return service;
}
- 4.1.2 這里我們看到Register & Start谁不，service是傳進(jìn)來的Installer類
- 4.1.3 Installer類是系統(tǒng)安裝apk的服務(wù)類坐梯，需要啟動(dòng)Installer服務(wù)之后才可以啟動(dòng)其他系統(tǒng)服務(wù)。 所以作為第一個(gè)啟動(dòng)的服務(wù)刹帕。
看一下onStart() 如何調(diào)用吵血？
@Override
public void onStart() {
Slog.i(TAG, "Waiting for installd to be ready.");
mInstaller.waitForConnection();
}
public void waitForConnection() {
for (;;) {
if (execute("ping") >= 0) {
return;
}
Slog.w(TAG, "installd not ready");
SystemClock.sleep(1000);
}
}
4.1.4 在 waitForConnection中 創(chuàng)建輪詢，不斷通過ping命令連接 Zygote進(jìn)程偷溺，因?yàn)锳ndroid中只有SystemServer和Zygote進(jìn)程通過socket方式通訊蹋辅，其他進(jìn)程通過Binder方式通訊。 只有在 SystemServer和Zygote 成功連接后亡蓉，才會(huì)啟動(dòng)其他的服務(wù)晕翠。
-
4.1.5 啟動(dòng)其他服務(wù)
- ActivityManagerService （SystemServiceManager.startService）
- PowerManagerService （SystemServiceManager.startService）
- LightsService（SystemServiceManager.startService）
- DisplayManagerService（SystemServiceManager.startService）
- PackageManagerService（PackageManagerService.main）通過ServiceManager.addService方法啟動(dòng)，再通過Binder機(jī)制與JNI交互
- UserManagerService（ServiceManager.addService）
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
ServiceManager.addService("package", m);
return m;
}
4.1.6 最后 startSensorService() 完成砍濒，以上這些服務(wù)有復(fù)雜的相互依賴關(guān)系淋肾，所以放在一起進(jìn)行初始化
-
4.2 startCoreServices() 啟動(dòng)無相互依賴的核心服務(wù)
- BatteryService
- UsageStatsManagerInternal
- WebViewUpdateService
private void startCoreServices() {
// Tracks the battery level. Requires LightService.
mSystemServiceManager.startService(BatteryService.class);
// Tracks application usage stats.
mSystemServiceManager.startService(UsageStatsService.class);
mActivityManagerService.setUsageStatsManager(
LocalServices.getService(UsageStatsManagerInternal.class));
// Update after UsageStatsService is available, needed before performBootDexOpt.
mPackageManagerService.getUsageStatsIfNoPackageUsageInfo();
// Tracks whether the updatable WebView is in a ready state and watches for update installs.
mSystemServiceManager.startService(WebViewUpdateService.class);
}
- 4.3 啟動(dòng)其他服務(wù) startOtherServices(),代碼太長就不貼了0.0（800行）
- 5.梳理一下
流程圖
