linux-kernel - Re: [PATCH v2 1/2] proc: Use PIDTYPE_TGID in next

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Message-ID: <20200424172914.GA26802@redhat.com>
Date:   Fri, 24 Apr 2020 19:29:15 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Alexey Gladkov <legion@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Gladkov <gladkov.alexey@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 1/2] proc: Use PIDTYPE_TGID in next_tgid

On 04/23, Eric W. Biederman wrote:
>
> @@ -3360,20 +3360,8 @@ static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter ite
>  	pid = find_ge_pid(iter.tgid, ns);
>  	if (pid) {
>  		iter.tgid = pid_nr_ns(pid, ns);
> -		iter.task = pid_task(pid, PIDTYPE_PID);
> -		/* What we to know is if the pid we have find is the
> -		 * pid of a thread_group_leader.  Testing for task
> -		 * being a thread_group_leader is the obvious thing
> -		 * todo but there is a window when it fails, due to
> -		 * the pid transfer logic in de_thread.
> -		 *
> -		 * So we perform the straight forward test of seeing
> -		 * if the pid we have found is the pid of a thread
> -		 * group leader, and don't worry if the task we have
> -		 * found doesn't happen to be a thread group leader.
> -		 * As we don't care in the case of readdir.
> -		 */
> -		if (!iter.task || !has_group_leader_pid(iter.task)) {
> +		iter.task = pid_task(pid, PIDTYPE_TGID);
> +		if (!iter.task) {
>  			iter.tgid += 1;
>  			goto retry;
>  		}

Acked-by: Oleg Nesterov <oleg@...hat.com>