Re: [PATCH v2 2/2] prctl: propagate has_child_subreaper flag to every descendant

[Oleg Nesterov <oleg@redhat.com>]

On 01/27, Pavel Tikhomirov wrote:
>
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1725,6 +1725,8 @@ struct task_struct {
>  	struct signal_struct *signal;
>  	struct sighand_struct *sighand;
>  
> +	struct list_head csr_descendant;
> +

You forgot to remove this part ;)

> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1367,9 +1367,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
>  	sig->oom_score_adj = current->signal->oom_score_adj;
>  	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
>  
> -	sig->has_child_subreaper = current->signal->has_child_subreaper ||
> -				   current->signal->is_child_subreaper;
> -
>  	mutex_init(&sig->cred_guard_mutex);
>  
>  	return 0;
> @@ -1800,6 +1797,13 @@ static __latent_entropy struct task_struct *copy_process(
>  
>  			p->signal->leader_pid = pid;
>  			p->signal->tty = tty_kref_get(current->signal->tty);
> +			/*
> +			 * Inherit has_child_subreaper flag under the same
> +			 * tasklist_lock with adding child to the process tree
> +			 * for propagate_has_child_subreaper optimization.
> +			 */
> +			p->signal->has_child_subreaper = current->signal->has_child_subreaper ||
> +							 current->signal->is_child_subreaper;

Ah yes, we need this change too...

And perhaps it would be more correct to do

			p->signal->has_child_subreaper =
				p->real_parent->signal->has_child_subreaper ||
				p->real_parent->signal->is_child_subreaper;

the current code is not exactly right if CLONE_PARENT...

Oleg.