linux-kernel - Re: [RFC][PATCH 09/14] genirq: add irq_kmemdump

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Message-ID: <f916cf7f-6d0d-4d31-8e4b-24fc7da13f4d@linaro.org>
Date: Fri, 13 Jun 2025 17:33:22 +0300
From: Eugen Hristev <eugen.hristev@...aro.org>
To: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
 linux-arm-msm@...r.kernel.org
Cc: linux-doc@...r.kernel.org, corbet@....net, mingo@...hat.com,
 rostedt@...dmis.org, john.ogness@...utronix.de, senozhatsky@...omium.org,
 pmladek@...e.com, peterz@...radead.org, mojha@....qualcomm.com,
 linux-arm-kernel@...ts.infradead.org, vincent.guittot@...aro.org,
 konradybcio@...nel.org, dietmar.eggemann@....com, juri.lelli@...hat.com,
 andersson@...nel.org
Subject: Re: [RFC][PATCH 09/14] genirq: add irq_kmemdump_register



On 5/7/25 13:27, Eugen Hristev wrote:
> 
> 
> On 5/7/25 13:18, Thomas Gleixner wrote:
>>
>> $Subject: ... See
>>
>> https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-submission-notes
>>
>> On Tue, Apr 22 2025 at 14:31, Eugen Hristev wrote:
>>> Add function to register irq info into kmemdump.
>>
>> What is irq info? Please explain explicitly which information is exposed
>> and why.
>>
>>>  
>>> +void irq_kmemdump_register(void)
>>> +{
>>> +	kmemdump_register("irq", (void *)&nr_irqs, sizeof(nr_irqs));
>>> +}
>>> +EXPORT_SYMBOL_GPL(irq_kmemdump_register);
>>
>> Are you going to slap a gazillion of those register a single variable
>> functions all over the place?
>>
>> That's a really horrible idea.
>>
>> The obvious way to deal with that is to annotate the variable:
>>
>> static unsigned int nr_irqs = NR_IRQS;
>> KMEMDUMP_VAR(nr_irqs);
>>
>> Let KMEMDUMP_VAR() store the size and the address of 'nr_irqs' in a
>> kmemdump specific section and then kmemdump can just walk that section
>> and dump stuff. No magic register functions and no extra storage
>> management for static/global variables.
>>
>> No?
> 
> Thank you very much for your review ! I will try it out.

I have tried this way and it's much cleaner ! thanks for the suggestion.

The thing that I am trying to figure out now is how to do something
similar for a dynamically allocated memory, e.g.
void *p = kmalloc(...);
and then I can annotate `p` itself, it's address and size, but what I
would also want to so dump the whole memory region pointed out by p. and
that area address and size cannot be figured out at compile time hence I
can't instantiate a struct inside the dedicated section for it.
Any suggestion on how to make that better ? Or just keep the function
call to register the area into kmemdump ?

Thanks again,
Eugen
> 
> Eugen
>>
>> Thanks,
>>
>>         tglx
>