From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: linux-mm@kvack.org, Roman Gushchin <guro@fb.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 0/3] rework mmap-exit vs. oom_reaper handover
Date: Thu, 13 Sep 2018 15:40:32 +0200 [thread overview]
Message-ID: <20180913134032.GF20287@dhcp22.suse.cz> (raw)
In-Reply-To: <0897639b-a1d9-2da1-0a1e-a3eeed799a0f@i-love.sakura.ne.jp>
On Thu 13-09-18 20:53:24, Tetsuo Handa wrote:
> On 2018/09/13 20:35, Michal Hocko wrote:
> >> Next question.
> >>
> >> /* Use -1 here to ensure all VMAs in the mm are unmapped */
> >> unmap_vmas(&tlb, vma, 0, -1);
> >>
> >> in exit_mmap() will now race with the OOM reaper. And unmap_vmas() will handle
> >> VM_HUGETLB or VM_PFNMAP or VM_SHARED or !vma_is_anonymous() vmas, won't it?
> >> Then, is it guaranteed to be safe if the OOM reaper raced with unmap_vmas() ?
> >
> > I do not understand the question. unmap_vmas is basically MADV_DONTNEED
> > and that doesn't require the exclusive mmap_sem lock so yes it should be
> > safe those two to race (modulo bugs of course but I am not aware of any
> > there).
> >
>
> You need to verify that races we observed with VM_LOCKED can't happen
> for VM_HUGETLB / VM_PFNMAP / VM_SHARED / !vma_is_anonymous() cases.
Well, VM_LOCKED is kind of special because that is not a permanent state
which might change. VM_HUGETLB, VM_PFNMAP resp VM_SHARED are not changed
throughout the vma lifetime.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-09-13 13:40 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-08 4:54 [PATCH v2] mm, oom: Fix unnecessary killing of additional processes Tetsuo Handa
2018-09-10 9:54 ` Michal Hocko
2018-09-10 11:27 ` Tetsuo Handa
2018-09-10 11:40 ` Michal Hocko
2018-09-10 12:52 ` Tetsuo Handa
2018-09-10 12:55 ` [RFC PATCH 0/3] rework mmap-exit vs. oom_reaper handover Michal Hocko
2018-09-10 12:55 ` [RFC PATCH 1/3] mm, oom: rework mmap_exit vs. oom_reaper synchronization Michal Hocko
2018-09-10 12:55 ` [RFC PATCH 2/3] mm, oom: keep retrying the oom_reap operation as long as there is substantial memory left Michal Hocko
2018-09-10 12:55 ` [RFC PATCH 3/3] mm, oom: hand over MMF_OOM_SKIP to exit path if it is guranteed to finish Michal Hocko
2018-09-10 14:59 ` [RFC PATCH 0/3] rework mmap-exit vs. oom_reaper handover Tetsuo Handa
2018-09-10 15:11 ` Michal Hocko
2018-09-10 15:40 ` Tetsuo Handa
2018-09-10 16:44 ` Michal Hocko
2018-09-12 3:06 ` Tetsuo Handa
2018-09-12 7:18 ` Michal Hocko
2018-09-12 7:58 ` Tetsuo Handa
2018-09-12 8:17 ` Michal Hocko
2018-09-12 10:59 ` Tetsuo Handa
2018-09-12 11:22 ` Michal Hocko
2018-09-11 14:01 ` Tetsuo Handa
2018-09-12 7:50 ` Michal Hocko
2018-09-12 13:42 ` Michal Hocko
2018-09-13 2:44 ` Tetsuo Handa
2018-09-13 9:09 ` Michal Hocko
2018-09-13 11:20 ` Tetsuo Handa
2018-09-13 11:35 ` Michal Hocko
2018-09-13 11:53 ` Tetsuo Handa
2018-09-13 13:40 ` Michal Hocko [this message]
2018-09-14 13:54 ` Tetsuo Handa
2018-09-14 14:14 ` Michal Hocko
2018-09-14 17:07 ` Tetsuo Handa
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