android 启动新 app 的activity 新进程的创建

上面是说到 activity的启动，看到进程启动的地方就结束了。
现在看看process的启动过程

  final ProcessRecord startProcessLocked(String processName, ApplicationInfo info,
            boolean knownToBeDead, int intentFlags, String hostingType, ComponentName hostingName,
            boolean allowWhileBooting, boolean isolated, int isolatedUid, boolean keepIfLarge,
            String abiOverride, String entryPoint, String[] entryPointArgs, Runnable crashHandler) {
        long startTime = SystemClock.elapsedRealtime();
        ProcessRecord app;

   //app ==null的时候，是全新启动一个应用，上面的代码略过

        if (app == null) {
            checkTime(startTime, "startProcess: creating new process record");

 //根据上面 启动activity 读到的 ApplicationInfo 创建相应的processinfo
 //在系统的pkglist中 注册应用的packagename 等等，填写相应的uid 之类的信息。

            app = newProcessRecordLocked(info, processName, isolated, isolatedUid);
            if (app == null) {
                Slog.w(TAG, "Failed making new process record for "
                        + processName + "/" + info.uid + " isolated=" + isolated);
                return null;
            }

            //此时的crashHandler 还是null

            app.crashHandler = crashHandler;
            mProcessNames.put(processName, app.uid, app);
            if (isolated) {
                mIsolatedProcesses.put(app.uid, app);
            }
            checkTime(startTime, "startProcess: done creating new process record");
        } else {
            // If this is a new package in the process, add the package to the list
            app.addPackage(info.packageName, info.versionCode, mProcessStats);
            checkTime(startTime, "startProcess: added package to existing proc");
        }

        // If the system is not ready yet, then hold off on starting this
        // process until it is.
        if (!mProcessesReady
                && !isAllowedWhileBooting(info)
                && !allowWhileBooting) {
            if (!mProcessesOnHold.contains(app)) {
                mProcessesOnHold.add(app);
            }
            if (DEBUG_PROCESSES) Slog.v(TAG, "System not ready, putting on hold: " + app);
            checkTime(startTime, "startProcess: returning with proc on hold");
            return app;
        }

        checkTime(startTime, "startProcess: stepping in to startProcess");
        startProcessLocked(
                app, hostingType, hostingNameStr, abiOverride, entryPoint, entryPointArgs);
        checkTime(startTime, "startProcess: done starting proc!");
        return (app.pid != 0) ? app : null;
    }



真正的启动 startProcessLocked（）

private final void startProcessLocked(ProcessRecord app, String hostingType,
String hostingNameStr, String abiOverride, String entryPoint, String[] entryPointArgs) {
long startTime = SystemClock.elapsedRealtime();
if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG,
“startProcessLocked removing on hold: ” + app);
mProcessesOnHold.remove(app);

    //唤醒cpu
    updateCpuStats();


    try {
        int uid = app.uid;

//略过 给process 标记debug 标志

//cpu 类型
String requiredAbi = (abiOverride != null) ? abiOverride : app.info.primaryCpuAbi;
if (requiredAbi == null) {
requiredAbi = Build.SUPPORTED_ABIS[0];
}

        String instructionSet = null;
        if (app.info.primaryCpuAbi != null) {
            instructionSet = VMRuntime.getInstructionSet(app.info.primaryCpuAbi);
        }

//填写配置文件

        boolean isActivityProcess = (entryPoint == null);
        if (entryPoint == null) entryPoint = "android.app.ActivityThread";
        checkTime(startTime, "startProcess: asking zygote to start proc");

//这个就是大名鼎鼎的 孵化器了
//zygote process 大概描述一下，向zygote process发送请求，申请一个新
//的进程，并把这个进程的pid返回回来，这样一个新的进程就被创建出来了。
//连同这activitythread 直接被创建出来process 直接运行main函数，主线程也被创建出来

        Process.ProcessStartResult startResult = Process.start(entryPoint,
                app.processName, uid, uid, gids, debugFlags, mountExternal,
                app.info.targetSdkVersion, app.info.seinfo, requiredAbi, instructionSet,
                app.info.dataDir, entryPointArgs);
        checkTime(startTime, "startProcess: returned from zygote!");

        if (app.isolated) {
            mBatteryStatsService.addIsolatedUid(app.uid, app.info.uid);
        }
        mBatteryStatsService.noteProcessStart(app.processName, app.info.uid);
        checkTime(startTime, "startProcess: done updating battery stats");

        EventLog.writeEvent(EventLogTags.AM_PROC_START,
                UserHandle.getUserId(uid), startResult.pid, uid,
                app.processName, hostingType,
                hostingNameStr != null ? hostingNameStr : "");

        if (app.persistent) {
            Watchdog.getInstance().processStarted(app.processName, startResult.pid);
        }

        checkTime(startTime, "startProcess: building log message");
        StringBuilder buf = mStringBuilder;
        buf.setLength(0);
        buf.append("Start proc ");
        buf.append(startResult.pid);
        buf.append(':');
        buf.append(app.processName);
        buf.append('/');
        UserHandle.formatUid(buf, uid);
        if (!isActivityProcess) {
            buf.append(" [");
            buf.append(entryPoint);
            buf.append("]");
        }
        buf.append(" for ");
        buf.append(hostingType);
        if (hostingNameStr != null) {
            buf.append(" ");
            buf.append(hostingNameStr);
        }
        Slog.i(TAG, buf.toString());
        app.setPid(startResult.pid);
        app.usingWrapper = startResult.usingWrapper;
        app.removed = false;
        app.killed = false;
        app.killedByAm = false;
        checkTime(startTime, "startProcess: starting to update pids map");
        synchronized (mPidsSelfLocked) {
            this.mPidsSelfLocked.put(startResult.pid, app);
            if (isActivityProcess) {
                Message msg = mHandler.obtainMessage(PROC_START_TIMEOUT_MSG);
                msg.obj = app;
                mHandler.sendMessageDelayed(msg, startResult.usingWrapper
                        ? PROC_START_TIMEOUT_WITH_WRAPPER : PROC_START_TIMEOUT);
            }
        }
        checkTime(startTime, "startProcess: done updating pids map");
    } catch (RuntimeException e) {
        // XXX do better error recovery.
        app.setPid(0);
        mBatteryStatsService.noteProcessFinish(app.processName, app.info.uid);
        if (app.isolated) {
            mBatteryStatsService.removeIsolatedUid(app.uid, app.info.uid);
        }
        Slog.e(TAG, "Failure starting process " + app.processName, e);
    }
}

“`