Re: [PATCH v3 0/1] pidfd: implement PIDFD_THREAD flag for pidfd_open()

[Oleg Nesterov <oleg@redhat.com>]

Before I forget this...

After this patch we can easily add another feature, pidfd_poll()
can add, say, POLLHUP to poll_flags if the pid is "dead".

So the user can do

	poll(pidfd, { .revents = POLLHUP });

and it will block until release_task() is called and this pid is
no longer in use (pid_task() == NULL).

Do you think this can be useful?

Oleg.