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Date:   Tue, 19 Sep 2023 15:42:18 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.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, 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,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        linux-m68k@lists.linux-m68k.org,
        Richard Weinberger <richard@nod.at>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
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        linux-hexagon@vger.kernel.org,
        Richard Henderson <richard.henderson@linaro.org>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>, linux-alpha@vger.kernel.org
Subject: Re: Arches that don't support PREEMPT
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On Tue, Sep 19, 2023 at 03:37:24PM +0200, John Paul Adrian Glaubitz wrote:
> On Tue, 2023-09-19 at 14:00 +0100, Matthew Wilcox wrote:
> > On Tue, Sep 19, 2023 at 02:30:59PM +0200, Thomas Gleixner 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
> > 
> > Sounds like three-and-a-half architectures which could be queued up for
> > removal right behind ia64 ...
> 
> The agreement to kill off ia64 wasn't an invitation to kill off other stuff
> that people are still working on! Can we please not do this?

If you're working on one of them, then surely it's a simple matter of
working on adding CONFIG_PREEMPT support :-)