linux-kernel - Re: [PATCH v5] x86/split_lock: fix delayed detection enabling

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Message-ID: <8aa58cf6-646a-4676-add5-63f5b41f9842@yandex-team.ru>
Date: Tue, 18 Mar 2025 23:43:35 +0300
From: Maksim Davydov <davydov-max@...dex-team.ru>
To: Ingo Molnar <mingo@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
 den-plotnikov@...dex-team.ru, gpiccoli@...lia.com, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com, tglx@...utronix.de, hpa@...or.com
Subject: Re: [PATCH v5] x86/split_lock: fix delayed detection enabling



On 3/18/25 23:24, Ingo Molnar wrote:
> 
> * Maksim Davydov <davydov-max@...dex-team.ru> wrote:
> 
>> If the warn mode with disabled mitigation mode is used, then on each
>> CPU where the split lock occurred detection will be disabled in order to
>> make progress and delayed work will be scheduled, which then will enable
>> detection back. Now it turns out that all CPUs use one global delayed
>> work structure. This leads to the fact that if a split lock occurs on
>> several CPUs at the same time (within 2 jiffies), only one CPU will
>> schedule delayed work, but the rest will not. The return value of
>> schedule_delayed_work_on() would have shown this, but it is not checked
>> in the code.
> 
> So we already merged the previous version into the locking tree ~10
> days ago and it's all in -next already:
> 
>    c929d08df8be ("x86/split_lock: Fix the delayed detection logic")
> 
>    https://web.git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=c929d08df8bee855528b9d15b853c892c54e1eee
> 
> Is there anything new in your -v5 patch, other than undoing all the
> changelog cleanups I did for the previous version? ;-)
> 

Oh, sorry, I missed it.
Yes, in v5 initcall is used instead of deferred initialization.
Either v4 or v5 are good for me. Please be free to choose the more 
convenient variant for you. :-)

> Thanks,
> 
> 	Ingo

-- 
Best regards,
Maksim Davydov