linux-kernel - Re: [PATCH] arch, mm: introduce arch_tlb_gather_mmu

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Message-ID: <CA+55aFw3NKzVO3xivjV1MzFH_wC1-eVAvgkHjpp7T7__CF6+eg@mail.gmail.com>
Date:   Tue, 5 Dec 2017 10:31:12 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Minchan Kim <minchan@...nel.org>,
        Andrea Argangeli <andrea@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] arch, mm: introduce arch_tlb_gather_mmu_exit

On Tue, Dec 5, 2017 at 6:58 AM, Michal Hocko <mhocko@...nel.org> wrote:
>
> This all is nice but tlb_gather users are not aware of that and this can
> actually cause some real problems. E.g. the oom_reaper tries to reap the
> whole address space but it might race with threads accessing the memory [1].
> It is possible that soft-dirty handling might suffer from the same
> problem [2] as soon as it starts supporting the feature.

So we fixed the oom reaper to just do proper TLB invalidates in commit
687cb0884a71 ("mm, oom_reaper: gather each vma to prevent leaking TLB
entry").

So now "fullmm" should be the expected "exit" case, and it all should
be unambiguous.

Do we really have any reason to apply this patch any more?

                Linus