linux-kernel - Re: [PATCH v11 14/26] locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread

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Date: Mon, 12 Feb 2024 16:16:41 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Byungchul Park <byungchul@...com>
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Subject: Re: [PATCH v11 14/26] locking/lockdep, cpu/hotplus: Use a weaker
 annotation in AP thread

On Tue, Jan 30 2024 at 11:58, Byungchul Park wrote:
> On Fri, Jan 26, 2024 at 06:30:02PM +0100, Thomas Gleixner wrote:
>> On Wed, Jan 24 2024 at 20:59, Byungchul Park wrote:
>> 
>> Why is lockdep in the subsystem prefix here? You are changing the CPU
>> hotplug (not hotplus) code, right?
>> 
>> > cb92173d1f0 ("locking/lockdep, cpu/hotplug: Annotate AP thread") was
>> > introduced to make lockdep_assert_cpus_held() work in AP thread.
>> >
>> > However, the annotation is too strong for that purpose. We don't have to
>> > use more than try lock annotation for that.
>> 
>> This lacks a proper explanation why this is too strong.
>> 
>> > Furthermore, now that Dept was introduced, false positive alarms was
>> > reported by that. Replaced it with try lock annotation.
>> 
>> I still have zero idea what this is about.
>
> 1. can track PG_locked that is a potential deadlock trigger.
>
>    https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.park@lge.com/

Sure, but that wants to be explicitely explained in the changelog and
not with a link. 'Now that Dept was introduced ...' is not an
explanation.

Thanks,

        tglx