linux-kernel - Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

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Date:   Tue, 29 Nov 2016 12:14:48 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Babu Moger <babu.moger@...cle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Tejun Heo <tj@...nel.org>, Sam Ravnborg <sam@...nborg.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

CC linux-renesas-soc

On Tue, Sep 27, 2016 at 9:33 PM, Babu Moger <babu.moger@...cle.com> wrote:
> These patches limit the static allocations for lockdep data structures
> used for debugging locking correctness. For sparc, all the kernel's code,
> data, and bss, must have locked translations in the TLB so that we don't
> get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> entries available that may be locked down, and with a 4mb page size,
> this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> limit and cause system boot-up problems. These patches limit the static
> allocations so that everything fits in current required size limit.
>
> patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> Patch 2 : Adjusts the sizes based on the new config parameter

Cool, this is also useful on other platforms!
E.g. on r8a7791/koelsch, I cannot boot an shmobile_defconfig plus
CONFIG_PROVE_LOCKING kernel.
Forcing CONFIG_PROVE_LOCKING_SMALL=y in Kconfig fixes that.

Should it become a user-selectable symbol?

> v2-> v3:
>    Some more comments from Sam Ravnborg and Peter Zijlstra.
>    Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
>    arch/sparc/Kconfig.
>
> v1-> v2:
>    As suggested by Peter Zijlstra, keeping the default as is.
>    Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
>    to handle sparc specific case.
>
> v0:
>    Initial revision.
>
> Babu Moger (2):
>   config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL
>     for sparc
>   lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined
>
>  arch/sparc/Kconfig                 |    1 +
>  kernel/locking/lockdep_internals.h |   20 +++++++++++++++++---
>  lib/Kconfig.debug                  |    3 +++
>  3 files changed, 21 insertions(+), 3 deletions(-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds