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

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Message-ID: <CAHk-=wizB-G40OxALNnz3-uNxuEAPf95H9hubAPeG2r2mrhwHA@mail.gmail.com>
Date:   Tue, 19 Sep 2023 11:52:22 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...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, mgorman@...e.de,
        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, 19 Sept 2023 at 11:37, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> We could simply leave the cond_resched() around but defined as nops for
> everything but the "nostalgia club" to keep them from having any regressions.

I doubt the nostalgia club cares about some latencies (that are
usually only noticeable under extreme loads anyway).

And if they do, maybe that would make somebody sit down and look into
doing it right.

So I think keeping it around would actually be both useless and
counter-productive.

              Linus