linux-kernel - Re: [PATCH v2 7/9] sched: define TIF_ALLOW

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Message-ID: <CAMuHMdXRsYNhui=Xh6Hmw5OZpG57uLf4y66L9r_wfAHOqn7prw@mail.gmail.com>
Date:   Fri, 6 Oct 2023 15:01:37 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ankur Arora <ankur.a.arora@...cle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        akpm@...ux-foundation.org, luto@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        willy@...radead.org, mgorman@...e.de, rostedt@...dmis.org,
        jon.grimm@....com, bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        jgross@...e.com, andrew.cooper3@...rix.com,
        Linux OpenRISC <linux-openrisc@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED

Hi Thomas,

On Tue, Sep 19, 2023 at 9:57 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> Though it just occured to me that there are dragons lurking:
>
> arch/alpha/Kconfig:     select ARCH_NO_PREEMPT
> arch/hexagon/Kconfig:   select ARCH_NO_PREEMPT
> arch/m68k/Kconfig:      select ARCH_NO_PREEMPT if !COLDFIRE
> arch/um/Kconfig:        select ARCH_NO_PREEMPT
>
> So we have four architectures which refuse to enable preemption points,
> i.e. the only model they allow is NONE and they rely on cond_resched()
> for breaking large computations.

Looks like there is a fifth one hidden: although openrisc does not
select ARCH_NO_PREEMPT, it does not call preempt_schedule_irq() or
select GENERIC_ENTRY?

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