问来自ProcessBuilder的Android ProcessBuilder: readLine()返回null

EN

private void startOpenVPNThreadArgs(String[] argv, Map<String, String> env) {
        LinkedList<String> argvlist = new LinkedList<String>();

        Collections.addAll(argvlist, argv);

        ProcessBuilder pb = new ProcessBuilder(argvlist);
        // Hack O rama

        String lbpath = genLibraryPath(argv, pb);

        pb.environment().put("LD_LIBRARY_PATH", lbpath);

        // Add extra variables
        for(Entry<String,String> e:env.entrySet()){
            pb.environment().put(e.getKey(), e.getValue());
        }
        pb.redirectErrorStream(true);
        try {
            mProcess = pb.start();
            // Close the output, since we don't need it
            mProcess.getOutputStream().close();
            InputStream in = mProcess.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(in));

            while(true) {
                String logline = br.readLine();
                if(logline==null) {
                    System.out.println("logline == null");
                    return;
                }