From: Yong-Taek Lee <ytk.lee@samsung.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Yong-Taek Lee <ytk.lee@samsung.com>,
"mhocko@kernel.org" <mhocko@kernel.org>,
"mhocko@suse.com" <mhocko@suse.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: Re: [PATCH] mm, oom_adj: avoid meaningless loop to find processes sharing mm
Date: Mon, 08 Oct 2018 15:14:07 +0900 [thread overview]
Message-ID: <20181008061407epcms1p519703ae6373a770160c8f912c7aa9521@epcms1p5> (raw)
In-Reply-To: <af7ae9c4-d7f1-69af-58fa-ec6949161f5b@I-love.SAKURA.ne.jp>
>On 2018/10/08 10:19, Yong-Taek Lee wrote:
>> @@ -1056,6 +1056,7 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
>> struct mm_struct *mm = NULL;
>> struct task_struct *task;
>> int err = 0;
>> + int mm_users = 0;
>>
>> task = get_proc_task(file_inode(file));
>> if (!task)
>> @@ -1092,7 +1093,8 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
>> struct task_struct *p = find_lock_task_mm(task);
>>
>> if (p) {
>> - if (atomic_read(&p->mm->mm_users) > 1) {
>> + mm_users = atomic_read(&p->mm->mm_users);
>> + if ((mm_users > 1) && (mm_users != get_nr_threads(p))) {
>
> How can this work (even before this patch)? When clone(CLONE_VM without CLONE_THREAD/CLONE_SIGHAND)
> is requested, copy_process() calls copy_signal() in order to copy sig->oom_score_adj and
> sig->oom_score_adj_min before calling copy_mm() in order to increment mm->mm_users, doesn't it?
> Then, we will get two different "struct signal_struct" with different oom_score_adj/oom_score_adj_min
> but one "struct mm_struct" shared by two thread groups.
>
Are you talking about race between __set_oom_adj and copy_process?
If so, i agree with your opinion. It can not set oom_score_adj properly for copied process if __set_oom_adj
check mm_users before copy_process calls copy_mm after copy_signal. Please correct me if i misunderstood anything.
>> mm = p->mm;
>> atomic_inc(&mm->mm_count);
>> }
next prev parent reply other threads:[~2018-10-08 6:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20181008011931epcms1p82dd01b7e5c067ea99946418bc97de46a@epcms1p8>
2018-10-08 1:19 ` [PATCH] mm, oom_adj: avoid meaningless loop to find processes sharing mm Yong-Taek Lee
2018-10-08 2:52 ` Tetsuo Handa
[not found] ` <CGME20181008011931epcms1p82dd01b7e5c067ea99946418bc97de46a@epcms1p5>
2018-10-08 6:14 ` Yong-Taek Lee [this message]
2018-10-08 6:22 ` Tetsuo Handa
[not found] ` <CGME20181008011931epcms1p82dd01b7e5c067ea99946418bc97de46a@epcms1p2>
2018-10-08 8:38 ` Yong-Taek Lee
2018-10-08 9:27 ` Tetsuo Handa
2018-10-09 6:35 ` Michal Hocko
2018-10-09 7:50 ` Michal Hocko
2018-10-09 10:00 ` Tetsuo Handa
2018-10-09 11:10 ` Michal Hocko
2018-10-09 12:52 ` Tetsuo Handa
2018-10-09 12:58 ` Michal Hocko
2018-10-09 13:14 ` Tetsuo Handa
2018-10-09 13:26 ` Michal Hocko
2018-10-09 13:51 ` Tetsuo Handa
2018-10-09 14:09 ` Michal Hocko
2018-10-09 8:02 ` Michal Hocko
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