linux-kernel - Re: [PATCH v14 10/12] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel

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Message-ID: <0871F5E6-5169-4FB6-A77B-7D8B54D91E51@infradead.org>
Date:   Sat, 11 Mar 2023 14:25:40 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Usama Arif <usama.arif@...edance.com>, kim.phillips@....com,
        brgerst@...il.com
CC:     piotrgorski@...hyos.org, oleksandr@...alenko.name,
        arjan@...ux.intel.com, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, x86@...nel.org,
        pbonzini@...hat.com, paulmck@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        thomas.lendacky@....com, seanjc@...gle.com, pmenzel@...gen.mpg.de,
        fam.zheng@...edance.com, punit.agrawal@...edance.com,
        simon.evans@...edance.com, liangma@...ngbit.com,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>
Subject: Re: [PATCH v14 10/12] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel



On 11 March 2023 14:14:53 GMT, Thomas Gleixner <tglx@...utronix.de> wrote:
>On Sat, Mar 11 2023 at 09:55, David Woodhouse wrote:
>> On Sat, 2023-03-11 at 10:54 +0200, Thomas Gleixner wrote:
>> I think I'll do it with a 'bool unpoison' argument to
>> idle_thread_get(). Or just make it unconditional; they're idempotent
>> anyway and cheap enough? Kind of weird to be doing it from finish_cpu()
>> though, so I'll probably stick with the argument.
>
>Eew.

Hm? I prefer the idea that idle_thread_get() is able to just return a *usable* one, and that we don't rely on architectures to have the *same* set of functions to unpoison/prepare it, and keep those duplicates in sync...

I suppose we could make a separate make_that_idle_thread_you_gave_me_actually_useful() function and avoid the duplication of anything but *that* call... but meh.