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Message-ID: <bd664a61-4506-bab0-19c3-0011f57005b5@cambridgegreys.com>
Date:   Tue, 19 Sep 2023 15:21:39 +0100
From:   Anton Ivanov <anton.ivanov@...bridgegreys.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.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, 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,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org,
        Richard Weinberger <richard@....at>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Brian Cain <bcain@...cinc.com>,
        linux-hexagon@...r.kernel.org,
        Richard Henderson <richard.henderson@...aro.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>, linux-alpha@...r.kernel.org
Subject: Re: Arches that don't support PREEMPT

On 19/09/2023 14:42, Peter Zijlstra wrote:
> 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 :-)

In the case of UML adding preempt will be quite difficult. I looked at this a few years back.

At the same time it is used for kernel test and other stuff. It is not exactly abandonware on a CPU found in archaeological artifacts of past civilizations like ia64.

> 
> _______________________________________________
> linux-um mailing list
> linux-um@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
> 

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

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