linux-kernel - Re: [PATCH RESEND] x86/split_lock: Make split lock mitigation sleep duration configurable

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Message-ID: <20251030191057.GDaQO4QYoZytxdQW_c@fat_crate.local>
Date: Thu, 30 Oct 2025 20:10:57 +0100
From: Borislav Petkov <bp@...en8.de>
To: Fushuai Wang <wangfushuai@...du.com>
Cc: tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	gpiccoli@...lia.com, peterz@...radead.org,
	davydov-max@...dex-team.ru, martin.petersen@...cle.com,
	jani.nikula@...el.com, joel.granados@...nel.org, xin@...or.com,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH RESEND] x86/split_lock: Make split lock mitigation sleep
 duration configurable

On Tue, Oct 28, 2025 at 05:43:33PM +0800, Fushuai Wang wrote:
> Commit 727209376f49 ("x86/split_lock: Add sysctl to control the misery
> mode") introduce a sysctl 'sysctl_sld_mitigate' to control the misery
> mode for split lock detection (0 to disable, 1 to enable). However,
> when enabled, the sleep duration for split lockers was fixed at 10 ms.
> 
> This patch extands 'sysctl_sld_mitigate' to allow configuring the sleep
> duration in milliseconds. Now, when 'sysctl_sld_mitigate' is set to
> N (N > 0), split lockers will sleep for N milliseconds.

I'm reading this and the only question that pops up in my mind is "why".

Why does the upstream kernel need this?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette