[Please keep the bug address on the CC list.]

> From: 仇之东 <0x4ec7@gmail.com>
> Date: Thu, 29 Jun 2017 19:49:01 +0800
>
> I reproduced this issue, the errno is 10.

Thanks.  errno 10 is ECHILD, right?  Can you verify in your system's
errno.h header file?

Paul, isn't it strange that waitpid exits with errno = ECHILD when it
waits for a specific PID?  What can we do against such calamities?
accept it like we do with EINTR?