本文转载自Gityuan的博客,原文地址为:http://gityuan.com/2016/02/21/activity-manager-service/
转载请注明作者及原文链接。
基于Android 6.0的源码剖析, 分析Android系统服务ActivityManagerService,简称AMS
frameworks/base/core/java/android/app/
- ActivityThread.java
- LoadedApk.java
- ContextImpl.java
frameworks/base/services/java/com/android/server/
- SystemServer.java
frameworks/base/services/core/java/com/android/server/
- SystemServiceManager.java
- ServiceThread.java
- pm/Installer.java
- am/ActivityManagerService.java
一、概述
Android系统启动-SystemServer篇(二)中有讲到AMS,本文以AMS为主线,讲述system_server进程中AMS服务的启动过程,以startBootstrapServices()方法为起点,紧跟着startCoreServices(), startOtherServices()共3个方法。
二. AMS启动过程
2.1 startBootstrapServices
[-> SystemServer.java]
private void startBootstrapServices() {
...
//启动AMS服务【见小节2.2】
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
//设置AMS的系统服务管理器
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
//设置AMS的APP安装器
mActivityManagerService.setInstaller(installer);
//初始化AMS相关的PMS
mActivityManagerService.initPowerManagement();
...
//设置SystemServer【见小节2.3】
mActivityManagerService.setSystemProcess();
}
2.2 启动AMS服务
SystemServiceManager.startService(ActivityManagerService.Lifecycle.class) 功能主要:
- 创建ActivityManagerService.Lifecycle对象;
- 调用Lifecycle.onStart()方法。
2.1.1 AMS.Lifecycle
[-> ActivityManagerService.java]
public static final class Lifecycle extends SystemService {
private final ActivityManagerService mService;
public Lifecycle(Context context) {
super(context);
//创建ActivityManagerService【见小节2.1.2】
mService = new ActivityManagerService(context);
}
@Override
public void onStart() {
mService.start(); //【见小节2.1.3】
}
public ActivityManagerService getService() {
return mService;
}
}
该过程:创建AMS内部类的Lifecycle,已经创建AMS对象,并调用AMS.start();
2.1.2 AMS创建
public ActivityManagerService(Context systemContext) {
mContext = systemContext;
mFactoryTest = FactoryTest.getMode();//默认为FACTORY_TEST_OFF
mSystemThread = ActivityThread.currentActivityThread();
//创建名为"ActivityManager"的前台线程,并获取mHandler
mHandlerThread = new ServiceThread(TAG, android.os.Process.THREAD_PRIORITY_FOREGROUND, false);
mHandlerThread.start();
mHandler = new MainHandler(mHandlerThread.getLooper());
//通过UiThread类,创建名为"android.ui"的线程
mUiHandler = new UiHandler();
//前台广播接收器,在运行超过10s将放弃执行
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", BROADCAST_FG_TIMEOUT, false);
//后台广播接收器,在运行超过60s将放弃执行
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", BROADCAST_BG_TIMEOUT, true);
mBroadcastQueues[0] = mFgBroadcastQueue;
mBroadcastQueues[1] = mBgBroadcastQueue;
//创建ActiveServices,其中非低内存手机mMaxStartingBackground为8
mServices = new ActiveServices(this);
mProviderMap = new ProviderMap(this);
//创建目录/data/system
File dataDir = Environment.getDataDirectory();
File systemDir = new File(dataDir, "system");
systemDir.mkdirs();
//创建服务BatteryStatsService
mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);
mBatteryStatsService.getActiveStatistics().readLocked();
...
//创建进程统计服务,信息保存在目录/data/system/procstats,
mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"), mHandler);
mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml"));
// User 0是第一个,也是唯一的一个开机过程中运行的用户
mStartedUsers.put(UserHandle.USER_OWNER, new UserState(UserHandle.OWNER, true));
mUserLru.add(UserHandle.USER_OWNER);
updateStartedUserArrayLocked();
...
//CPU使用情况的追踪器执行初始化
mProcessCpuTracker.init();
...
mRecentTasks = new RecentTasks(this);
// 创建ActivityStackSupervisor对象
mStackSupervisor = new ActivityStackSupervisor(this, mRecentTasks);
mTaskPersister = new TaskPersister(systemDir, mStackSupervisor, mRecentTasks);
//创建名为"CpuTracker"的线程
mProcessCpuThread = new Thread("CpuTracker") {
public void run() {
while (true) {
synchronized(this) {
final long now = SystemClock.uptimeMillis();
long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now;
long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now;
if (nextWriteDelay < nextCpuDelay) {
nextCpuDelay = nextWriteDelay;
}
if (nextCpuDelay > 0) {
mProcessCpuMutexFree.set(true);
this.wait(nextCpuDelay);
}
}
updateCpuStatsNow(); //更新CPU状态
}
}
};
...
}
该过程共创建了3个线程,分别为”ActivityManager”,”android.ui”,”CpuTracker”。
2.1.3 AMS.start
private void start() {
Process.removeAllProcessGroups(); //移除所有的进程组
mProcessCpuThread.start(); //启动CpuTracker线程
mBatteryStatsService.publish(mContext); //启动电池统计服务
mAppOpsService.publish(mContext);
//创建LocalService,并添加到LocalServices
LocalServices.addService(ActivityManagerInternal.class, new LocalService());
}
2.3 AMS.setSystemProcess
public void setSystemProcess() {
try {
ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
ServiceManager.addService("meminfo", new MemBinder(this));
ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
ServiceManager.addService("dbinfo", new DbBinder(this));
if (MONITOR_CPU_USAGE) {
ServiceManager.addService("cpuinfo", new CpuBinder(this));
}
ServiceManager.addService("permission", new PermissionController(this));
ServiceManager.addService("processinfo", new ProcessInfoService(this));
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS);
//【见小节2.3.1】
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
synchronized (this) {
//创建ProcessRecord对象
ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);
app.persistent = true; //设置为persistent进程
app.pid = MY_PID;
app.maxAdj = ProcessList.SYSTEM_ADJ;
app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.put(app.pid, app);
}
updateLruProcessLocked(app, false, null);//维护进程lru
updateOomAdjLocked(); //更新adj
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException("", e);
}
}
该方法主要工作是注册各种服务。
2.3.1 AT.installSystemApplicationInfo
[-> ActivityThread.java]
public void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
synchronized (this) {
getSystemContext().installSystemApplicationInfo(info, classLoader);
mProfiler = new Profiler(); //创建用于性能统计的Profiler对象
}
}
该方法调用ContextImpl的nstallSystemApplicationInfo()方法,最终调用LoadedApk的installSystemApplicationInfo,加载名为“android”的package
2.3.2 installSystemApplicationInfo
[-> LoadedApk.java]
void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
assert info.packageName.equals("android");
mApplicationInfo = info; //将包名为"android"的应用信息保存到mApplicationInfo
mClassLoader = classLoader;
}
2.4 startOtherServices
private void startOtherServices() {
...
//安装系统Provider 【见小节2.4.1】
mActivityManagerService.installSystemProviders();
...
//phase480 && 500
mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);
mSystemServiceManager.startBootPhase(SystemService.PHASE_SYSTEM_SERVICES_READY);
...
//【见小节3.1】
mActivityManagerService.systemReady(new Runnable() {
public void run() {
//phase550
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
...
//phase600
mSystemServiceManager.startBootPhase(
SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
...
}
}
}
2.4.1 AMS.installSystemProviders
public final void installSystemProviders() {
List<ProviderInfo> providers;
synchronized (this) {
ProcessRecord app = mProcessNames.get("system", Process.SYSTEM_UID);
providers = generateApplicationProvidersLocked(app);
if (providers != null) {
for (int i=providers.size()-1; i>=0; i--) {
ProviderInfo pi = (ProviderInfo)providers.get(i);
//移除非系统的provider
if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0) {
providers.remove(i);
}
}
}
}
if (providers != null) {
//安装所有的系统provider
mSystemThread.installSystemProviders(providers);
}
// 创建核心Settings Observer,用于监控Settings的改变。
mCoreSettingsObserver = new CoreSettingsObserver(this);
}
三. AMS.systemReady
AMS.systemReady()方法的参数为Runable类型的goingCallback, 该方法执行简单划分以下几部分:
public void systemReady(final Runnable goingCallback) {
before goingCallback; // 见小节[3.1]
goingCallback.run(); // 见小节[3.2]
after goingCallback; // 见小节[3.3]
}
3.1 before goingCallback
synchronized(this) {
if (mSystemReady) { //首次为flase,则不进入该分支
if (goingCallback != null) {
goingCallback.run();
}
return;
}
mRecentTasks.clear();
//恢复最近任务栏的task
mRecentTasks.addAll(mTaskPersister.restoreTasksLocked());
mRecentTasks.cleanupLocked(UserHandle.USER_ALL);
mTaskPersister.startPersisting();
if (!mDidUpdate) {
if (mWaitingUpdate) {
return;
}
final ArrayList<ComponentName> doneReceivers = new ArrayList<ComponentName>();
//处于升级过程【见小节3.1.1】
mWaitingUpdate = deliverPreBootCompleted(new Runnable() {
public void run() {
synchronized (ActivityManagerService.this) {
mDidUpdate = true;
}
showBootMessage(mContext.getText(
R.string.android_upgrading_complete),
false);
writeLastDonePreBootReceivers(doneReceivers);
systemReady(goingCallback);
}
}, doneReceivers, UserHandle.USER_OWNER);
if (mWaitingUpdate) {
return;
}
mDidUpdate = true;
}
mAppOpsService.systemReady();
mSystemReady = true;
}
ArrayList<ProcessRecord> procsToKill = null;
synchronized(mPidsSelfLocked) {
for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {
ProcessRecord proc = mPidsSelfLocked.valueAt(i);
//非persistent进程,加入procsToKill
if (!isAllowedWhileBooting(proc.info)){
if (procsToKill == null) {
procsToKill = new ArrayList<ProcessRecord>();
}
procsToKill.add(proc);
}
}
}
synchronized(this) {
if (procsToKill != null) {
//杀掉procsToKill中的进程, 杀掉进程且不允许重启
for (int i=procsToKill.size()-1; i>=0; i--) {
ProcessRecord proc = procsToKill.get(i);
removeProcessLocked(proc, true, false, "system update done");
}
}
mProcessesReady = true; //process处于ready状态
}
Slog.i(TAG, "System now ready");
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_AMS_READY,
SystemClock.uptimeMillis());
该阶段的主要功能:
- 向PRE_BOOT_COMPLETED的接收者发送广播;
- 杀掉procsToKill中的进程, 杀掉进程且不允许重启;
- 此时,系统和进程都处于ready状态;
3.1.1 deliverPreBootCompleted
private boolean deliverPreBootCompleted(final Runnable onFinishCallback, ArrayList<ComponentName> doneReceivers, int userId) {
Intent intent = new Intent(Intent.ACTION_PRE_BOOT_COMPLETED);
List<ResolveInfo> ris = AppGlobals.getPackageManager().queryIntentReceivers(
intent, null, 0, userId);
//对于FLAG_SYSTEM=false的app直接过滤掉
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);
if (userId == UserHandle.USER_OWNER) {
ArrayList<ComponentName> lastDoneReceivers = readLastDonePreBootReceivers();
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--;
doneReceivers.add(comp);
}
}
}
...
PreBootContinuation cont = new PreBootContinuation(intent, onFinishCallback,
doneReceivers, ris, users); //【见小节3.1.2】
cont.go(); //【见小节3.1.3】
return true;
}
3.1.2 PreBootContinuation
[-> ActivityManagerService.java ::PreBootContinuation]
final class PreBootContinuation extends IIntentReceiver.Stub {
PreBootContinuation(Intent _intent, Runnable _onFinishCallback,
ArrayList<ComponentName> _doneReceivers, List<ResolveInfo> _ris, int[] _users) {
intent = _intent;
onFinishCallback = _onFinishCallback;
doneReceivers = _doneReceivers;
ris = _ris;
users = _users;
}
}
3.1.3 PreBootContinuation.go
void go() {
if (lastRi != curRi) {
ActivityInfo ai = ris.get(curRi).activityInfo;
ComponentName comp = new ComponentName(ai.packageName, ai.name);
intent.setComponent(comp);
doneReceivers.add(comp);
lastRi = curRi;
CharSequence label = ai.loadLabel(mContext.getPackageManager());
showBootMessage(mContext.getString(R.string.android_preparing_apk, label), false);
}
//发送广播
broadcastIntentLocked(null, null, intent, null, this,
0, null, null, null, AppOpsManager.OP_NONE,
null, true, false, MY_PID, Process.SYSTEM_UID, users[curUser]);
}
3.2 goingCallback.run()
此处的goingCallback,便是在startOtherServices()过程中传递进来的参数
private void startOtherServices() {
...
mActivityManagerService.systemReady(new Runnable() {
public void run() {
//phase550
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
mActivityManagerService.startObservingNativeCrashes();
//启动WebView
WebViewFactory.prepareWebViewInSystemServer();
//启动系统UI【见小节3.2.1】
startSystemUi(context);
// 执行一系列服务的systemReady方法
networkScoreF.systemReady();
networkManagementF.systemReady();
networkStatsF.systemReady();
networkPolicyF.systemReady();
connectivityF.systemReady();
audioServiceF.systemReady();
Watchdog.getInstance().start(); //Watchdog开始工作
//phase600
mSystemServiceManager.startBootPhase(
SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
//执行一系列服务的systemRunning方法
wallpaper.systemRunning();
inputMethodManager.systemRunning(statusBarF);
location.systemRunning();
countryDetector.systemRunning();
networkTimeUpdater.systemRunning();
commonTimeMgmtService.systemRunning();
textServiceManagerService.systemRunning();
assetAtlasService.systemRunning();
inputManager.systemRunning();
telephonyRegistry.systemRunning();
mediaRouter.systemRunning();
mmsService.systemRunning();
}
});
}
该过程启动各种进程:
- 启动阶段550,回调相应onBootPhase()方法;
- 启动WebView,并且会创建进程,这是zygote正式创建的第一个进程;
- 启动systemui服务;
- …
3.2.1 startSystemUi
static final void startSystemUi(Context context) {
Intent intent = new Intent();
intent.setComponent(new ComponentName("com.android.systemui",
"com.android.systemui.SystemUIService"));
context.startServiceAsUser(intent, UserHandle.OWNER);
}
启动服务”com.android.systemui/.SystemUIService”
3.3 after goingCallback
//启动【见小节3.3.1】
mSystemServiceManager.startUser(mCurrentUserId);
synchronized (this) {
if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
//通过pms获取所有的persistent进程
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")) {
//启动persistent进程
addAppLocked(info, false, null);
}
}
}
}
mBooting = true;
// 启动桌面Activity 【见小节3.3.2】
startHomeActivityLocked(mCurrentUserId, "systemReady");
...
long ident = Binder.clearCallingIdentity();
try {
//system发送广播USER_STARTED
Intent intent = new Intent(Intent.ACTION_USER_STARTED);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY
| Intent.FLAG_RECEIVER_FOREGROUND);
intent.putExtra(Intent.EXTRA_USER_HANDLE, mCurrentUserId);
broadcastIntentLocked(...);
//system发送广播USER_STARTING
intent = new Intent(Intent.ACTION_USER_STARTING);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
intent.putExtra(Intent.EXTRA_USER_HANDLE, mCurrentUserId);
broadcastIntentLocked(...);
} finally {
Binder.restoreCallingIdentity(ident);
}
mStackSupervisor.resumeTopActivitiesLocked();
sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);
}
该阶段主要功能:
- 回调所有SystemService的onStartUser()方法;
- 启动persistent进程;
- 启动home Activity;
- 发送广播USER_STARTED和USER_STARTING;
- 恢复栈顶Activity;
- 发送广播USER_SWITCHED;
3.3.1 SSM.startUser
[-> SystemServiceManager.java]
public void startUser(final int userHandle) {
final int serviceLen = mServices.size();
for (int i = 0; i < serviceLen; i++) {
final SystemService service = mServices.get(i);
try {
//回调所有SystemService的onStartUser()方法
service.onStartUser(userHandle);
} catch (Exception ex) {
...
}
}
}
3.3.2 AMS.startHomeActivityLocked
boolean startHomeActivityLocked(int userId, String reason) {
//home intent有CATEGORY_HOME
Intent intent = getHomeIntent();
ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
if (aInfo != null) {
intent.setComponent(new ComponentName(
aInfo.applicationInfo.packageName, aInfo.name));
aInfo = new ActivityInfo(aInfo);
aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
ProcessRecord app = getProcessRecordLocked(aInfo.processName,
aInfo.applicationInfo.uid, true);
if (app == null || app.instrumentationClass == null) {
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
//启动桌面Activity
mStackSupervisor.startHomeActivity(intent, aInfo, reason);
}
}
return true;
}
四. 总结
- 创建AMS实例对象,创建Andoid Runtime,ActivityThread和Context对象;
- setSystemProcess:注册AMS、meminfo、cpuinfo等服务到ServiceManager;
- installSystemProviderss,加载SettingsProvider;
- 启动SystemUIService,再调用一系列服务的systemReady()方法;
4.1 发布Binder服务
[小节2.3]的AMS.setSystemProcess()过程向servicemanager注册了如下这个binder服务
服务名 | 类名 | 功能 |
---|---|---|
activity | ActivityManagerService | AMS |
procstats | ProcessStatsService | 进程统计 |
meminfo | MemBinder | 内存 |
gfxinfo | GraphicsBinder | 图像信息 |
dbinfo | DbBinder | 数据库 |
cpuinfo | CpuBinder | CPU |
permission | PermissionController | 权限 |
processinfo | ProcessInfoService | 进程服务 |
usagestats | UsageStatsService | 应用的使用情况 |
想要查看这些服务的信息,可通过dumpsys <服务名>
命令。比如查看CPU信息命令dumpsys cpuinfo
。
4.2 AMS.systemReady
另外,AMS.systemReady()的大致过程如下:
public final class ActivityManagerService{
public void systemReady(final Runnable goingCallback) {
...//更新操作
mSystemReady = true; //系统处于ready状态
removeProcessLocked(proc, true, false, "system update done");//杀掉所有非persistent进程
mProcessesReady = true; //进程处于ready状态
goingCallback.run(); //这里有可能启动进程
addAppLocked(info, false, null); //启动所有的persistent进程
mBooting = true; //正在启动中
startHomeActivityLocked(mCurrentUserId, "systemReady"); //启动桌面
mStackSupervisor.resumeTopActivitiesLocked(); //恢复栈顶的Activity
}
}
再说一说mProcessesReady
:
startProcessLocked()过程对于非persistent进程必须等待mProcessesReady = true才会真正创建进程,否则进程放入mProcessesOnHold队列。 当然以下情况不会判断mProcessesReady:
- addAppLocked()启动persistent进程; //但此时已经mProcessesReady;
- finishBooting()启动on-hold进程; //但此时已经mProcessesReady;
- cleanUpApplicationRecordLock() //启动需要restart进程,前提是进程已创建;
- attachApplicationLocked() //绑定Bind死亡通告失败,前台同样是进程要已创建。
还有一个特殊情况,可以创建进程:processNextBroadcast()过程对于flag为FLAG_RECEIVER_BOOT_UPGRADE的广播拉进程 ,只在小节3.1.1的升级过程会出现。
由此可见,mProcessesReady在没有ready前,则基本没有应用进程。