linux-kernel - Re: [PATCH 4.19 156/191] powerpc: Warn about use of smt_snooze

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Date:   Thu, 5 Nov 2020 20:23:05 +0100
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Joel Stanley <joel@....id.au>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 4.19 156/191] powerpc: Warn about use of smt_snooze_delay

Hi!

> From: Joel Stanley <joel@....id.au>
> 
> commit a02f6d42357acf6e5de6ffc728e6e77faf3ad217 upstream.
> 
> It's not done anything for a long time. Save the percpu variable, and
> emit a warning to remind users to not expect it to do anything.
> 
> This uses pr_warn_once instead of pr_warn_ratelimit as testing
> 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system showed the warning
> to be noisy, as the online/offline loop is slow.

I don't believe this is good idea for stable. It is in 5.9-rc2, and
likely mainline users will get userspace fixed, but that warning is
less useful for -stable users.

(And besides, it does not fix any serious bug).

Best regards,
								Pavel

-- 
http://www.livejournal.com/~pavelmachek

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