linux-kernel - Re: [PATCH 2/4] mm/tlb: Remove tlb_remove

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Date:   Wed, 22 Aug 2018 20:35:16 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Nick Piggin <npiggin@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andrew Lutomirski <luto@...nel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Will Deacon <will.deacon@....com>,
        Rik van Riel <riel@...riel.com>,
        Jann Horn <jannh@...gle.com>,
        Adin Scannell <ascannell@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        David Miller <davem@...emloft.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 2/4] mm/tlb: Remove tlb_remove_table() non-concurrent condition

On Wed, Aug 22, 2018 at 8:31 PM Nicholas Piggin <npiggin@...il.com> wrote:
>
>
> So that leaves speculative operations. I don't see where the problem is
> with those either -- this shortcut needs to ensure there are no other
> *non speculative* operations. mm_users is correct for that.

No. Because mm_users doesn't contain any lazy tlb users.

And yes, those lazy tlbs are all kernel threads, but they can still
speculatively load user addresses.

           Linus