linux-kernel - Re: general protection fault in oom_unkillable

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Message-ID: <20190617063118.GA30420@dhcp22.suse.cz>
Date:   Mon, 17 Jun 2019 08:31:18 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        syzbot <syzbot+d0fc9d3c166bc5e4a94b@...kaller.appspotmail.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        yuzhoujian@...ichuxing.com
Subject: Re: general protection fault in oom_unkillable_task

On Mon 17-06-19 00:13:47, Tetsuo Handa wrote:
[...]
> >From 415e52cf55bc4ad931e4f005421b827f0b02693d Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Date: Mon, 17 Jun 2019 00:09:38 +0900
> Subject: [PATCH] mm: memcontrol: Use CSS_TASK_ITER_PROCS at mem_cgroup_scan_tasks().
> 
> Since commit c03cd7738a83b137 ("cgroup: Include dying leaders with live
> threads in PROCS iterations") corrected how CSS_TASK_ITER_PROCS works,
> mem_cgroup_scan_tasks() can use CSS_TASK_ITER_PROCS in order to check
> only one thread from each thread group.

O(Threads#) is definitely much worse than O(proc#)

> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!

> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ba9138a..b09ff45 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1163,7 +1163,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
>  		struct css_task_iter it;
>  		struct task_struct *task;
>  
> -		css_task_iter_start(&iter->css, 0, &it);
> +		css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it);
>  		while (!ret && (task = css_task_iter_next(&it)))
>  			ret = fn(task, arg);
>  		css_task_iter_end(&it);
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs