linux-kernel - Re: [PATCH] panic: only warn about deprecated panic

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Message-ID: <e93ee2bc-b9ca-44cd-a690-be1465500d56@nvidia.com>
Date: Mon, 12 Jan 2026 08:48:37 +0200
From: Gal Pressman <gal@...dia.com>
To: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Petr Mladek <pmladek@...e.com>, Andrew Morton
 <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 Mark Bloch <mbloch@...dia.com>, Nimrod Oren <noren@...dia.com>
Subject: Re: [PATCH] panic: only warn about deprecated panic_print on write
 access

On 12/01/2026 5:32, Feng Tang wrote:
> On Sun, Jan 11, 2026 at 10:28:55AM +0200, Gal Pressman wrote:
>> On 08/01/2026 17:52, Petr Mladek wrote:
>>> On Wed 2026-01-07 15:20:44, Feng Tang wrote:
>>>> On Wed, Jan 07, 2026 at 08:41:22AM +0200, Gal Pressman wrote:
>>>>> On 07/01/2026 5:00, Feng Tang wrote:
>>>>>>> @@ -1014,7 +1015,6 @@ static int panic_print_set(const char *val, const struct kernel_param *kp)
>>>>>>>  
>>>>>>>  static int panic_print_get(char *val, const struct kernel_param *kp)
>>>>>>>  {
>>>>>>> -	panic_print_deprecated();
>>>>>>
>>>>>> Actually this was intentional, in one of the patch version, this
>>>>>> panic_print_get() was not there but reusing the param_get_ulong().
>>>>>>
>>>>>> It was added later as sometimes developer do want to runtime check
>>>>>> the current 'panic_print' setting through /sys/module/kernel/parameters/
>>>>>> interface, and I thought it may be better to give the warning.
>>>>>
>>>>> I figured it would make sense to keep the behaviors consistent.
>>>
>>> I see.
>>>
>>>> When people run 'sysctl -a', in 99.9% cases, the users don't care
>>>> 'panic_print' or even don't know what 'panic_print' is, that's why
>>>> I think removing it makes sense.
>>>>
>>>> But for a user running 'cat /sys/module/kernel/parameters/panic_rint',
>>>> giving a warning is meaningful.
>>>
>>> Makes perfect sense.
>>>
>>> We need to make people aware that "panic_print" will eventually go
>>> away. 'sysctl -a' is different because it prints all values and
>>> there is big chance that the caller is not interested in "panic_print"
>>> at all.
>>>
>>> It makes sense to remove the warning from sysctl read. But I would
>>> keep it in sysfs read.
>>
>> The sysfs entry exhibits the same issue, just different command:
>>
>> # systool -m kernel -v
>>
>> Or:
>>
>> # grep . /sys/module/kernel/parameters/*
> 
> Yes, when user checks the kernel parameters, I think it's better to
> give them a notice (it's a pr_info_once(), which only prints once
> for the whole power cycle).
This log message causes a lot of noise for people who have no idea what
panic_print is.
We started seeing this print internally, and it took a long time and
significant resources to figure out what changed and if we were doing
anything wrong in our environments.

Seeing a deprecation notice is alarming, especially if you don't know
what is being deprecated or how it affects you. In my opinion, we
shouldn't print this unless someone actually uses panic_print.