From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] mm, oom: marks all killed tasks as oom victims
Date: Mon, 22 Oct 2018 19:56:49 +0900 [thread overview]
Message-ID: <93f99371-cff8-fc31-a594-eecdff299f16@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20181022104341.GY18839@dhcp22.suse.cz>
On 2018/10/22 19:43, Michal Hocko wrote:
> On Mon 22-10-18 18:42:30, Tetsuo Handa wrote:
>> On 2018/10/22 17:48, Michal Hocko wrote:
>>> On Mon 22-10-18 16:58:50, Tetsuo Handa wrote:
>>>> Michal Hocko wrote:
>>>>> --- a/mm/oom_kill.c
>>>>> +++ b/mm/oom_kill.c
>>>>> @@ -898,6 +898,7 @@ static void __oom_kill_process(struct task_struct *victim)
>>>>> if (unlikely(p->flags & PF_KTHREAD))
>>>>> continue;
>>>>> do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID);
>>>>> + mark_oom_victim(p);
>>>>> }
>>>>> rcu_read_unlock();
>>>>>
>>>>> --
>>>>
>>>> Wrong. Either
>>>
>>> You are right. The mm might go away between process_shares_mm and here.
>>> While your find_lock_task_mm would be correct I believe we can do better
>>> by using the existing mm that we already have. I will make it a separate
>>> patch to clarity.
>>
>> Still wrong. p->mm == NULL means that we are too late to set TIF_MEMDIE
>> on that thread. Passing non-NULL mm to mark_oom_victim() won't help.
>
> Why would it be too late? Or in other words why would this be harmful?
>
Setting TIF_MEMDIE after exit_mm() completed is too late.
static void exit_mm(void)
{
(...snipped...)
task_lock(current);
current->mm = NULL;
up_read(&mm->mmap_sem);
enter_lazy_tlb(mm, current);
task_unlock(current);
mm_update_next_owner(mm);
mmput(mm);
if (test_thread_flag(TIF_MEMDIE))
exit_oom_victim();
}
next prev parent reply other threads:[~2018-10-22 10:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-22 7:13 [RFC PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2018-10-22 7:13 ` [RFC PATCH 1/2] mm, oom: marks all killed tasks as oom victims Michal Hocko
2018-10-22 7:58 ` Tetsuo Handa
2018-10-22 8:48 ` Michal Hocko
2018-10-22 9:42 ` Tetsuo Handa
2018-10-22 10:43 ` Michal Hocko
2018-10-22 10:56 ` Tetsuo Handa [this message]
2018-10-22 11:12 ` Michal Hocko
2018-10-22 11:16 ` [RFC PATCH v2 " Michal Hocko
2018-10-22 7:13 ` [RFC PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Michal Hocko
2018-10-22 11:45 ` Tetsuo Handa
2018-10-22 12:03 ` Michal Hocko
2018-10-22 13:20 ` Tetsuo Handa
2018-10-22 13:43 ` Michal Hocko
2018-10-22 15:12 ` Tetsuo Handa
2018-10-23 1:01 ` Tetsuo Handa
2018-10-23 11:42 ` Michal Hocko
2018-10-23 12:10 ` Michal Hocko
2018-10-23 12:33 ` Tetsuo Handa
2018-10-23 12:48 ` Michal Hocko
2018-10-26 14:25 ` Johannes Weiner
2018-10-26 19:25 ` Michal Hocko
2018-10-26 19:33 ` Michal Hocko
2018-10-27 1:10 ` Tetsuo Handa
2018-11-06 9:44 ` Tetsuo Handa
2018-11-06 12:42 ` Michal Hocko
2018-11-07 9:45 ` Tetsuo Handa
2018-11-07 10:08 ` Michal Hocko
2018-12-07 12:43 ` Tetsuo Handa
2018-12-12 10:23 ` Tetsuo Handa
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