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

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Message-ID: <aWRrPm64i3QKVca7@U-2FWC9VHC-2323.local>
Date: Mon, 12 Jan 2026 11:32:14 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Gal Pressman <gal@...dia.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 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).

Thanks,
Feng