linux-kernel - Re: [PATCH v3] do_wait: make PIDTYPE

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Message-ID: <dd410f8c-4ab6-107e-8ae9-4b35be0d8885@torproject.org>
Date:   Thu, 11 Mar 2021 10:26:02 -0600
From:   Jim Newsome <jnewsome@...project.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christian Brauner <christian@...uner.io>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] do_wait: make PIDTYPE_PID case O(1) instead of O(n)


On 3/11/21 09:15, Oleg Nesterov wrote:
> 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.

Oops! Thanks; got it. v4 coming shortly