linux-kernel - Re: [PATCH v2] mm,oom: exclude oom_task_origin processes if they are OOM-unkillable.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160218120849.GC18149@dhcp22.suse.cz>
Date:	Thu, 18 Feb 2016 13:08:49 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	rientjes@...gle.com, akpm@...ux-foundation.org, mgorman@...e.de,
	oleg@...hat.com, torvalds@...ux-foundation.org, hughd@...gle.com,
	andrea@...nel.org, riel@...hat.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm,oom: exclude oom_task_origin processes if they are
 OOM-unkillable.

On Thu 18-02-16 19:30:12, Tetsuo Handa wrote:
[...]
> Commit 9cbb78bb314360a8 changed oom_scan_process_thread() to
> always pass memcg == NULL by removing memcg argument from
> oom_scan_process_thread(). As a result, after that commit,
> we are doing test_tsk_thread_flag(p, TIF_MEMDIE) check and
> oom_task_origin(p) check between two oom_unkillable_task()
> calls of memcg OOM case. Why don't we skip these checks by
> passing memcg != NULL to first oom_unkillable_task() call?
> Was this change by error?

I am not really sure I understand your question.  The point is
that mem_cgroup_out_of_memory does for_each_mem_cgroup_tree which
means that only tasks from the given memcg hierarchy is checked and
oom_unkillable_task cares about memcg only for

        /* When mem_cgroup_out_of_memory() and p is not member of the group */
        if (memcg && !task_in_mem_cgroup(p, memcg))
                return true;

which is never true by definition. I guess we can safely remove the memcg
argument from oom_badness and oom_unkillable_task. At least from a quick
glance...
-- 
Michal Hocko
SUSE Labs