framework——应用进程启动流程
1 前言
2 源码分析
2.1 ActivityManagerInternal 初始化流程
（1）请求启动应用进程的入口
/frameworks/base/services/core/java/com/android/server/wm/ActivityStackSupervisor.java
void startSpecificActivityLocked(ActivityRecord r, boolean andResume, boolean checkConfig) {
final WindowProcessController wpc = mService.getProcessController(r.processName, r.info.applicationInfo.uid);
...
//判断应用进程是否已创建，即 IApplicationThread 是否为空
if (wpc != null && wpc.hasThread()) {
try {
//启动 Activity
realStartActivityLocked(r, wpc, andResume, checkConfig);
return;
}
}
try {
...
//应用进程不存在，通知创建应用进程，mService 为 ATMS；mService.mAmInternal 为 ActivityManagerInternal
final Message msg = PooledLambda.obtainMessage(
ActivityManagerInternal::startProcess, mService.mAmInternal, r.processName,
r.info.applicationInfo, knownToBeDead, "activity", r.intent.getComponent());
mService.mH.sendMessage(msg);
}
...
}ActivityStackSupervisor 对象在 ATMS 的 initialize() 方法中创建，并将 ATMS 对象注入到 ActivityStackSupervisor 中。
PooledLambda.obtainMessage() 获取一个 Message，并为其指定 Callback，即执行 mService.mAmInternal 对象的 ActivityManagerInternal::startProcess 函数，函数入参为 r.processName、r.info.applicationInfo 等5个参数。由此可知，ActivityManagerInternal 的 startProcess() 方法是请求启动应用进程的起点。
ActivityManagerInternal 是抽象类，其实现类是 AMS 的内部类 LocalService。接下来将分析 ActivityManagerInternal 的创建流程和 ATMS 获取起对象的流程。
（2）ActivityManagerInternal 的创建
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
private void start() {
...
LocalServices.addService(ActivityManagerInternal.class, new LocalService());
//调用 ATMS 的 onActivityManagerInternalAdded 方法进一步初始化
mActivityTaskManager.onActivityManagerInternalAdded();
...
}start() 方法被 AMS.Lifecycle 的 onStart() 方法调用，onStart() 方法又被 SystemServiceManager 的 startService() 方法调用。
（3）ATMS 获取 ActivityManagerInternal
/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public void onActivityManagerInternalAdded() {
synchronized (mGlobalLock) {
mAmInternal = LocalServices.getService(ActivityManagerInternal.class);
...
}
}（4）LocalServices
public final class LocalServices {
...
private static final ArrayMap, Object> sLocalServiceObjects = new ArrayMap, Object>();
public static T getService(Class type) {
synchronized (sLocalServiceObjects) {
return (T) sLocalServiceObjects.get(type);
}
}
public static void addService(Class type, T service) {
synchronized (sLocalServiceObjects) {
...
sLocalServiceObjects.put(type, service);
}
}
...
} 2.2 AMS 到 ZygoteState
（1）startProcess
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.LocalService.java
public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead, String hostingType, ComponentName hostingName) {
try {
...
synchronized (ActivityManagerService.this) {
startProcessLocked(processName, info, knownToBeDead, 0 , new HostingRecord(hostingType, hostingName), false, false, true);
}
}
...
}（2）startProcessLocked
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
final ProcessRecord startProcessLocked(String processName, ApplicationInfo info, boolean knownToBeDead, int intentFlags,
HostingRecord hostingRecord, boolean allowWhileBooting, boolean isolated, boolean keepIfLarge) {
//mProcessList 在定义时就被初始化，即：final ProcessList mProcessList = new ProcessList()
return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags, hostingRecord,
allowWhileBooting, isolated, 0, keepIfLarge, null, null, null, null);
}（3）startProcessLocked
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
final ProcessRecord startProcessLocked(String processName, ApplicationInfo info, boolean knownToBeDead, int intentFlags,
HostingRecord hostingRecord, boolean allowWhileBooting, boolean isolated, int isolatedUid,
boolean keepIfLarge, String abiOverride, String entryPoint, String[] entryPointArgs, Runnable crashHandler) {
...
ProcessRecord app;
if (!isolated) {
app = getProcessRecordLocked(processName, info.uid, keepIfLarge);
...
}
...
if (app == null) {
...
} else {
app.addPackage(info.packageName, info.longVersionCode, mService.mProcessStats);
...
}
...
final boolean success = startProcessLocked(app, hostingRecord, abiOverride);
...
return success ? app : null;
}（4）startProcessLocked
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
final boolean startProcessLocked(ProcessRecord app, HostingRecord hostingRecord, String abiOverride) {
return startProcessLocked(app, hostingRecord, false, false, false, abiOverride);
}（5）startProcessLocked
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
boolean startProcessLocked(ProcessRecord app, HostingRecord hostingRecord, boolean disableHiddenApiChecks,
boolean disableTestApiChecks, boolean mountExtStorageFull, String abiOverride) {
...
try {
...
final String entryPoint = "android.app.ActivityThread";
return startProcessLocked(hostingRecord, entryPoint, app, uid, gids, runtimeFlags,
mountExternal, seInfo, requiredAbi, instructionSet, invokeWith, startTime);
}
...
}（6）startProcessLocked
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
boolean startProcessLocked(HostingRecord hostingRecord, String entryPoint, ProcessRecord app,
int uid, int[] gids, int runtimeFlags, int mountExternal, String seInfo,
String requiredAbi, String instructionSet, String invokeWith, long startTime) {
...
final long startSeq = app.startSeq = ++mProcStartSeqCounter;
...
mPendingStarts.put(startSeq, app);
if (mService.mConstants.FLAG_PROCESS_START_ASYNC) {
...
mService.mProcStartHandler.post(() -> {
try {
final Process.ProcessStartResult startResult = startProcess(app.hostingRecord,
entryPoint, app, app.startUid, gids, runtimeFlags, mountExternal,
app.seInfo, requiredAbi, instructionSet, invokeWith, app.startTime);
synchronized (mService) {
handleProcessStartedLocked(app, startResult, startSeq);
}
}
...
});
return true;
} else {
try {
final Process.ProcessStartResult startResult = startProcess(hostingRecord, entryPoint, app, uid, gids,
runtimeFlags, mountExternal, seInfo, requiredAbi, instructionSet, invokeWith, startTime);
handleProcessStartedLocked(app, startResult.pid, startResult.usingWrapper, startSeq, false);
}
...
return app.pid > 0;
}
}（7）startProcess
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
private Process.ProcessStartResult startProcess(HostingRecord hostingRecord, String entryPoint,
ProcessRecord app, int uid, int[] gids, int runtimeFlags, int mountExternal,
String seInfo, String requiredAbi, String instructionSet, String invokeWith, long startTime) {
try {
...
else {
startResult = Process.start(entryPoint, app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet, app.info.dataDir, invokeWith,
app.info.packageName, app.mDisabledCompatChanges, new String[]{PROC_START_SEQ_IDENT + app.startSeq});
}
...
return startResult;
}
...
}
（8）ProcessStartResult
/frameworks/base/core/java/android/os/Process.java
public static ProcessStartResult start(final String processClass, final String niceName, int uid, int gid, @Nullable int[] gids,
int runtimeFlags, int mountExternal, int targetSdkVersion, String seInfo, String abi, String instructionSet,
String appDataDir, String invokeWith, String packageName, long[] disabledCompatChanges, String[] zygoteArgs) {
return ZYGOTE_PROCESS.start(processClass, niceName, uid, gid, gids, runtimeFlags, mountExternal, targetSdkVersion,
seInfo, abi, instructionSet, appDataDir, invokeWith, packageName, true, disabledCompatChanges, zygoteArgs);
}（9）ProcessStartResult
/frameworks/base/core/java/android/os/Process.java
z（10）ProcessStartResult
/frameworks/base/core/java/android/os/Process.java
z（11）ProcessStartResult
/frameworks/base/core/java/android/os/Process.java
z2.3 ZygoteInit 到 ActivityThread