linux-kernel - Re: [RFC PATCH 0/8] Move task_struct::cpu back into thread

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Message-ID: <CAMj1kXGPcHwdSjy-doB09LBLvrXtqYT4dyxE5hU=D=2m8Fg8zg@mail.gmail.com>
Date:   Tue, 21 Sep 2021 14:06:24 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Mark Rutland <mark.rutland@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Keith Packard <keithpac@...zon.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@...ts.ozlabs.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "open list:S390" <linux-s390@...r.kernel.org>
Subject: Re: [RFC PATCH 0/8] Move task_struct::cpu back into thread_info

On Tue, 14 Sept 2021 at 15:55, Mark Rutland <mark.rutland@....com> wrote:
>
> On Tue, Sep 14, 2021 at 02:10:28PM +0200, Ard Biesheuvel wrote:
> > Commit c65eacbe290b ("sched/core: Allow putting thread_info into
> > task_struct") mentions that, along with moving thread_info into
> > task_struct, the cpu field is moved out of the former into the latter,
> > but does not explain why.
>
> From what I recall of talking to Andy around that time, when converting
> arm64 over, the theory was that over time we'd move more and more out of
> thread_info and into task_struct or thread_struct, until task_struct
> supplanted thread_info entirely, and that all became generic.
>
> I think the key gain there was making things more *generic*, and there
> are other ways we could do that in future without moving more into
> task_struct (e.g. with a geenric thread_info and arch_thread_info inside
> that).
>
> With that in mind, and given the diffstat, I think this is worthwhile.
>
> FWIW, for the series:
>
> Acked-by: Mark Rutland <mark.rutland@....com>
>

Thanks.

Any comments on this from the various arch maintainers? Especially
power, as Christophe seems happy with this but there are 3 different
patches affecting power that need a maintainer ack.