Re: + remove-the-likelypid-check-in-copy_process.patch added to -mm tree

[Oleg Nesterov <oleg@tv-sign.ru>]

Sukadev Bhattiprolu wrote:

> @@ -1237,26 +1237,24 @@ static struct task_struct *copy_process(
>  		}
>  	}
>
> -	if (likely(p->pid)) {
> -		add_parent(p);
> -		tracehook_init_task(p);
> -
> -		if (thread_group_leader(p)) {
> -			pid_t pgid = process_group(current);
> -			pid_t sid = process_session(current);
> -
> -			p->signal->tty = current->signal->tty;
> -			p->signal->pgrp = pgid;
> -			set_signal_session(p->signal, process_session(current));
> -			attach_pid(p, PIDTYPE_PGID, find_pid(pgid));
> -			attach_pid(p, PIDTYPE_SID, find_pid(sid));
> +	add_parent(p);

This means that idle threads (except "swapper") are visible to for_each_process()
and do_each_thread(). Looks dangerous and somewhat strange to me.

Could you explain this change?

Oleg.