linux-kernel - Re: [PATCH 06/13] locking/qspinlock: merge qspinlock

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Message-ID: <7e1a7093-2dbd-e5aa-3fae-9ade787cbd41@redhat.com>
Date:   Wed, 6 Jul 2022 09:35:48 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/13] locking/qspinlock: merge qspinlock_paravirt.h into
 qspinlock.c

On 7/5/22 13:20, Peter Zijlstra wrote:
> On Tue, Jul 05, 2022 at 12:38:13AM +1000, Nicholas Piggin wrote:
>> There isn't much reason to keep these separate.
> The reason was so that other paravirt implementations could be added.
>
> The CNA thing was also implemented this way...

Do you have any plan to take CNA [1] some time in the future?

Anyway, the main reason the paravirt code is separated into a separated 
file is to leave only the core part in qspinlock.c so that new users are 
overwhelmed with the messy details for the paravirt code. Putting 
everything into a single can make it harder to read for the newbies.

Also eliminating the preprocessor trick will make it harder to integrate 
a different qspinlock variant, like CNA, into the code base.

Cheers,
Longman

[1] 
https://lore.kernel.org/lkml/20210514200743.3026725-1-alex.kogan@oracle.com/