linux-kernel - Re: [PATCH] regulator: userspace-consumer: Use atomic operation

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Message-ID: <e1416ea3-9e20-4662-b394-bc9f842bfccb@hatter.bewilderbeest.net>
Date:   Thu, 24 Aug 2023 12:32:22 -0700
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Mark Brown <broonie@...nel.org>
Cc:     Naresh Solanki <naresh.solanki@...ements.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: userspace-consumer: Use atomic operation

On Thu, Aug 24, 2023 at 09:55:41AM PDT, Mark Brown wrote:
>On Thu, Aug 24, 2023 at 04:34:05PM +0530, Naresh Solanki wrote:
>> On Wed, 23 Aug 2023 at 20:41, Mark Brown <broonie@...nel.org> wrote:
>> > On Wed, Aug 23, 2023 at 04:15:57PM +0200, Naresh Solanki wrote:
>
>> > > Replace mutexes with atomic operations.
>
>> > Why?  Generally atomics are more complicated and hard to understand and
>> > get right.
>
>> Since the operations involved here are simple & short & can be managed by
>> atomic operation.
>
>Unless there's a strong positive reason to specifically use atomics it
>seems better to avoid them, like I say they're full of landmines with
>unexpeted behaviours and therefore something that sets off alarm bells
>about needing careful study, the mutex is going to be less preformant
>but is also much more clearly correct.

I assume this patch was posted as a result of a comment I made on the 
original patch [1], but in hindsight I probably shouldn't have suggested 
it as it's a relatively minor issue either way -- I think the other 
things brought up in that email are much more significant concerns.  
Honestly I don't think that patch should be applied in its present form, 
though I see it's still present in the regulator/for-next and 
regulator/for-6.6 branches -- Mark, do you intend to include it as-is in 
your pull request to Linus for the 6.6 merge window?

[1] https://lore.kernel.org/lkml/d3ea0fe2-00bb-493b-aca7-ba7a31bd3c78@hatter.bewilderbeest.net/


Zev