Make MultipleReader thread-safe
Make MultipleReader thread-safe

pkuyym/Paddle,Canpio/Paddle,chengduoZH/Paddle,reyoung/Paddle,QiJune/Paddle,Canpio/Paddle,jacquesqiao/Paddle,PaddlePaddle/Paddle,chengduoZH/Paddle,lcy-seso/Paddle,luotao1/Paddle,lcy-seso/Paddle,pkuyym/Paddle,QiJune/Paddle,baidu/Paddle,Canpio/Paddle,chengduoZH/Paddle,reyoung/Paddle,putcn/Paddle,putcn/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,QiJune/Paddle,PaddlePaddle/Paddle,baidu/Paddle,putcn/Paddle,baidu/Paddle,tensor-tang/Paddle,putcn/Paddle,pkuyym/Paddle,Canpio/Paddle,luotao1/Paddle,luotao1/Paddle,QiJune/Paddle,Canpio/Paddle,jacquesqiao/Paddle,pkuyym/Paddle,pkuyym/Paddle,PaddlePaddle/Paddle,Canpio/Paddle,reyoung/Paddle,jacquesqiao/Paddle,PaddlePaddle/Paddle,reyoung/Paddle,Canpio/Paddle,QiJune/Paddle,putcn/Paddle,jacquesqiao/Paddle,luotao1/Paddle,baidu/Paddle,luotao1/Paddle,lcy-seso/Paddle,Canpio/Paddle,QiJune/Paddle,pkuyym/Paddle,lcy-seso/Paddle,jacquesqiao/Paddle,baidu/Paddle,luotao1/Paddle,chengduoZH/Paddle,lcy-seso/Paddle,tensor-tang/Paddle,tensor-tang/Paddle,chengduoZH/Paddle,putcn/Paddle,PaddlePaddle/Paddle,lcy-seso/Paddle,jacquesqiao/Paddle,reyoung/Paddle,tensor-tang/Paddle,tensor-tang/Paddle,PaddlePaddle/Paddle,reyoung/Paddle