Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v3] do_wait: make PIDTYPE_PID case O(1) instead of O(n)
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christian Brauner <christian@brauner.io>,
        linux-kernel@vger.kernel.org
References: <20210309203919.15920-1-jnewsome@torproject.org>
 <m1blbqmy2u.fsf@fess.ebiederm.org>
 <4d9006b4-b65a-6ce0-b367-971f29de1f21@torproject.org>
 <20210311151542.GB15552@redhat.com>
From:   Jim Newsome <jnewsome@torproject.org>
Organization: The Tor Project
Message-ID: <dd410f8c-4ab6-107e-8ae9-4b35be0d8885@torproject.org>
Date:   Thu, 11 Mar 2021 10:26:02 -0600
MIME-Version: 1.0
In-Reply-To: <20210311151542.GB15552@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Precedence: bulk


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