linux-kernel - Re: [PATCH] ARC: Enable machine_desc->init_per

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Date:   Thu, 14 Jun 2018 22:26:12 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     "wbx@...ibc-ng.org" <wbx@...ibc-ng.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH] ARC: Enable machine_desc->init_per_cpu for non-SMP
 configs

Hi Vineet,

On Thu, 2017-11-30 at 09:46 -0800, Vineet Gupta wrote:
> On 11/29/2017 12:21 AM, Alexey Brodkin wrote:
> > As of today we assumed that "machine_desc->init_per_cpu" calls
> > are only usable on SMP systems when we want to run some piece of
> > code on early boot for each and every core, I guess assumption was
> > we have "machine_desc->init_early" for single-core cases where
> > the one and only master core can do all the things.
> > 
> > But it turned out for platforms which might be both UP and SMP it
> > might be benificial to use "init_per_cpu" for both UP and SMP cases
> > with which we achieve 2 things simultaneously:
> >   1) Exactly the same one code will be used for UP&SMP for
> >      things required to be done on each an every core regardless if it's
> >      a master and the only core in UP system or any other slave core in SMP
> >      setup.
> >   1) There will be no "ifdef CONFIG_SMP" around "init_per_cpu".
> > 
> 
> Seems fine to me. However this needs to go with the actual platform change which 
> needs it.

Well for example this might get in the way of building kernel for HSDK with
CONFIG_SMP disabled which is IMHO quite valid case in terms of testing
code-base compiled with no CONFIG_SMP (something Waldemar was up to).

Is it a strong enough reason for that patch to be applied?

-Alexey