Android之zygote源码剖析（三）

   static void preload(BootTimingsTraceLog bootTimingsTraceLog) {
        Log.d(TAG, "begin preload");
        bootTimingsTraceLog.traceBegin("BeginIcuCachePinning");
        beginIcuCachePinning();
        bootTimingsTraceLog.traceEnd(); // BeginIcuCachePinning
        bootTimingsTraceLog.traceBegin("PreloadClasses");
        preloadClasses();
        bootTimingsTraceLog.traceEnd(); // PreloadClasses
        bootTimingsTraceLog.traceBegin("PreloadResources");
        preloadResources();
        bootTimingsTraceLog.traceEnd(); // PreloadResources
        Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "PreloadOpenGL");
        preloadOpenGL();
        Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
        preloadSharedLibraries();
        preloadTextResources();
        // Ask the WebViewFactory to do any initialization that must run in the zygote process,
        // for memory sharing purposes.
        WebViewFactory.prepareWebViewInZygote();
        endIcuCachePinning();
        warmUpJcaProviders();
        Log.d(TAG, "end preload");

        sPreloadComplete = true;
    }

    void registerServerSocket(String socketName) {
        if (mServerSocket == null) {
            int fileDesc;
            // 构建名字为ANDROID_SOCKET_zygote
            final String fullSocketName = ANDROID_SOCKET_PREFIX + socketName;
            try {
                // 获取环境变量，并转换成数字
                String env = System.getenv(fullSocketName);
                fileDesc = Integer.parseInt(env);
            } catch (RuntimeException ex) {
                throw new RuntimeException(fullSocketName + " unset or invalid", ex);
            }

            try {
                // 创建文件描述符
                FileDescriptor fd = new FileDescriptor();
                fd.setInt$(fileDesc);
                // 根据文件描述符创建socket
                mServerSocket = new LocalServerSocket(fd);
            } catch (IOException ex) {
                throw new RuntimeException(
                        "Error binding to local socket '" + fileDesc + "'", ex);
            }
        }
    }

    private static boolean startSystemServer(String abiList, String socketName, ZygoteServer zygoteServer)
            throws Zygote.MethodAndArgsCaller, RuntimeException {
        ……
        /* Hardcoded command line to start the system server */
        String args[] = {
            "--setuid=1000",
            "--setgid=1000",
            "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1023,1032,3001,3002,3003,3006,3007,3009,3010",
            "--capabilities=" + capabilities + "," + capabilities,
            "--nice-name=system_server",
            "--runtime-args",
            "com.android.server.SystemServer",
        };
        ZygoteConnection.Arguments parsedArgs = null;

        int pid;

        try {
            parsedArgs = new ZygoteConnection.Arguments(args);
            ZygoteConnection.applyDebuggerSystemProperty(parsedArgs);
            ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs);

            // 创建子进程（SystemServer）
            pid = Zygote.forkSystemServer(
                    parsedArgs.uid, parsedArgs.gid,
                    parsedArgs.gids,
                    parsedArgs.debugFlags,
                    null,
                    parsedArgs.permittedCapabilities,
                    parsedArgs.effectiveCapabilities);
        } catch (IllegalArgumentException ex) {
            throw new RuntimeException(ex);
        }

        /* For child process */
        if (pid == 0) {
            if (hasSecondZygote(abiList)) {
                waitForSecondaryZygote(socketName);
            }

            // 关闭继承的zygoteServer的socket
            zygoteServer.closeServerSocket();
            // 处理systemServer逻辑
            handleSystemServerProcess(parsedArgs);
        }

        return true;
    }