Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD

[Oleg Nesterov]

On 02/10, Christian Brauner wrote:
>
> The question is what is more useful for userspace when they do:
> pidfd_send_signal(1234, PIDFD_SEND_PROCESS_GROUP)?
>
> (1) They either mean to signal a process group that is headed by 1234.

Yes, this is what I had in mind, see also another email from me.
Simple, clear, and matches kill(-1234).

> (2) Or they want to signal a process group of which 1234 is a member or
>     the leader.

Somehow I didn't even consider this option when I thought about
PIDFD_SIGNAL_PGRP...

> From a usability perspective (1) is a lot more restrictive because it
> requires @pidfd to refer to a process group leader.

Yes, but to be honest (2) doesn't fit my head. Probably simply because
I always had (1) in mind...

But I won't argue if you think that (2) has useful usecases.

Oleg.