Re: [PATCH v3] do_wait: make PIDTYPE_PID case O(1) instead of O(n)

[Oleg Nesterov]

On 03/10, Jim Newsome wrote:
>
> On 3/10/21 16:40, Eric W. Biederman wrote:
>
> >> +static int do_wait_pid(struct wait_opts *wo)
> >> +{
> >> +	struct task_struct *target = pid_task(wo->wo_pid, PIDTYPE_PID);
> >                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > This is subtle change in behavior.
> >
> > Today on the task->children list we only place thread group leaders.
>
> Shouldn't we allow waiting on clone children if __WALL or __WCLONE is set?

Don't confuse clone child with child's sub-thread.

Oleg.