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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 6 Oct 2023 15:01:37 +0200
Message-ID: <CAMuHMdXRsYNhui=Xh6Hmw5OZpG57uLf4y66L9r_wfAHOqn7prw@mail.gmail.com>
Subject: Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ankur Arora <ankur.a.arora@oracle.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
        akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com,
        juri.lelli@redhat.com, vincent.guittot@linaro.org,
        willy@infradead.org, mgorman@suse.de, rostedt@goodmis.org,
        jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com,
        boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
        jgross@suse.com, andrew.cooper3@citrix.com,
        Linux OpenRISC <linux-openrisc@vger.kernel.org>
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Hi Thomas,

On Tue, Sep 19, 2023 at 9:57 PM Thomas Gleixner <tglx@linutronix.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@linux-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