linux-kernel - Re: Arches that don't support PREEMPT

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Message-ID: <a428516ebeae71e33635edc83052c972ce40c85d.camel@physik.fu-berlin.de>
Date:   Tue, 19 Sep 2023 16:24:48 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Peter Zijlstra <peterz@...radead.org>
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>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        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 Tue, 2023-09-19 at 16:16 +0200, Peter Zijlstra wrote:
> > I find it a bit unfair that maintainers of architectures that have huge companies
> > behind them use their manpower to urge less popular architectures for removal just
> > because they don't have 150 people working on the port so they can keep up with
> > design changes quickly.
> 
> PREEMPT isn't something new. Also, I don't think the arch part for
> actually supporting it is particularly hard, mostly it is sticking the
> preempt_schedule_irq() call in return from interrupt code path.
> 
> If you convert the arch to generic-entry (a much larger undertaking)
> then you get this for free.

If the conversion isn't hard, why is the first reflex the urge to remove an architecture
instead of offering advise how to get the conversion done?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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