linux-kernel - Re: [PATCH 3/4] mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE

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Message-ID: <CA+55aFykjambbbvwap2C=B7yKzpy5-W6OiYG16E1RE7QLzODtg@mail.gmail.com>
Date:   Wed, 22 Aug 2018 14:34:27 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     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>, Nick Piggin <npiggin@...il.com>,
        David Miller <davem@...emloft.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 3/4] mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE

On Wed, Aug 22, 2018 at 8:46 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -180,6 +180,7 @@ config X86
>         select HAVE_PERF_REGS
>         select HAVE_PERF_USER_STACK_DUMP
>         select HAVE_RCU_TABLE_FREE
> +       select HAVE_RCU_TABLE_INVALIDATE        if HAVE_RCU_TABLE_FREE

This is confusing. First you select HAVE_RCU_TABLE_FREE
unconditionally, and then you select HAVE_RCU_TABLE_INVALIDATE based
on that unconditional variable.

I can see why you do it, but that's because I see the next patch. On
its own it just looks like you have a drinking problem.

That said, I was waiting to see if this patch-set would get any
comments before applying it, but it's been mostly crickets... So I
think I'll just apply it and get this issue over and done with.

              Linus