startProcessLocked函数分析

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所属分类：AMS 安卓

四个函数

final ProcessRecord startProcessLocked(String processName,
            ApplicationInfo info, boolean knownToBeDead, int intentFlags,
            String hostingType, ComponentName hostingName, boolean allowWhileBooting,
            boolean isolated, boolean keepIfLarge) {
        return startProcessLocked(processName, info, knownToBeDead, intentFlags, hostingType,
                hostingName, allowWhileBooting, isolated, 0 /* isolatedUid */, keepIfLarge,
                null /* ABI override */, null /* entryPoint */, null /* entryPointArgs */,
                null /* crashHandler */);
    }

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) {

private final void startProcessLocked(ProcessRecord app,
            String hostingType, String hostingNameStr) {
        startProcessLocked(app, hostingType, hostingNameStr, null /* abiOverride */,
                null /* entryPoint */, null /* entryPointArgs */);
    }

private final void startProcessLocked(ProcessRecord app, String hostingType,
            String hostingNameStr, String abiOverride, String entryPoint, String[] entryPointArgs) {

我们把四个startProcessLocked函数放在一块，前面两种调用的参数比较多，最后通过转换呢，都会转换到最后一个函数的形式。

我们来看下参数的意思：

ProcessRecord app ： 要启动的app的统一信息，一些uid啊等等都在里面

String hostingType ： 启动的一些标签比如后台启动什么的...

String hostingNameStr : 启动的标记比如会标记 brocast启动等待

String entryPoint ： 进程启动的进入点，一般是ActivityThread的main函数

String[] entryPointArgs ： 启动参数。

最后我们来具体分析下这个函数。

private final void startProcessLocked(ProcessRecord app, String hostingType,
            String hostingNameStr, String abiOverride, String entryPoint, String[] entryPointArgs) {


        if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG_PROCESSES,
                "startProcessLocked removing on hold: " + app);
        mProcessesOnHold.remove(app);

        updateCpuStats();
...

        try {
            try {
                final int userId = UserHandle.getUserId(app.uid);
                AppGlobals.getPackageManager().checkPackageStartable(app.info.packageName, userId);
            } catch (RemoteException e) {
                throw e.rethrowAsRuntimeException();
            }

...

            int uid = app.uid;
            int[] gids = null;
            int mountExternal = Zygote.MOUNT_EXTERNAL_NONE;
            if (!app.isolated) {

            }

            if (mFactoryTest != FactoryTest.FACTORY_TEST_OFF) {
                if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
                        && mTopComponent != null
                        && app.processName.equals(mTopComponent.getPackageName())) {
                    uid = 0;
                }
                if (mFactoryTest == FactoryTest.FACTORY_TEST_HIGH_LEVEL
                        && (app.info.flags&ApplicationInfo.FLAG_FACTORY_TEST) != 0) {
                    uid = 0;
                }
            }


            app.gids = gids;
            app.requiredAbi = requiredAbi;
            app.instructionSet = instructionSet;


            if (entryPoint == null) entryPoint = "android.app.ActivityThread";

            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);
            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");
            ProcessRecord oldApp;
            synchronized (mPidsSelfLocked) {
                oldApp = mPidsSelfLocked.get(startResult.pid);
            }
            if (oldApp != null && !app.isolated) {
                cleanUpApplicationRecordLocked(oldApp, false, false, -1,
                        true /*replacingPid*/);
            }
            synchronized (mPidsSelfLocked) {
                this.mPidsSelfLocked.put(startResult.pid, app);
            }
            checkTime(startTime, "startProcess: done updating pids map");
        } catch (RuntimeException e) {
            forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid), false,
                    false, true, false, false, UserHandle.getUserId(app.userId), "start failure");
        }
    }

其实一整段函数最重要的是这个Process.start

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);

在这个Process.start

之前它指定了，entryPoint = "android.app.ActivityThread"

之后是进程已经起来了对 app的一些信息的设置，比如pid

再之后是进行一些错误的检查。

OK，下文进行Process.start分析......

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