Messages in this thread | | | Date | Thu, 14 Dec 2017 15:05:04 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] arch, mm: introduce arch_tlb_gather_mmu_exit |
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On Tue 05-12-17 20:14:37, Michal Hocko wrote: > On Tue 05-12-17 10:31:12, Linus Torvalds wrote: > > On Tue, Dec 5, 2017 at 6:58 AM, Michal Hocko <mhocko@kernel.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? > > Well, the point was the clarity. The bad behavior came as a surprise for > the oom reaper and as Minchan mentioned we would see a similar problem > with soft-dirty bits as soon as they are supported on arm64 or > potentially other architectures which might do special handling for exit > case.
I am not going to push this patch if it is considered pointless but I haven't heard back anything to the above argument. -- Michal Hocko SUSE Labs
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