Re: [PATCH v3 5/5] panic: add note that panic_print sysctl interface is deprecated

[Petr Mladek <pmladek@suse.com>]

On Thu 2025-07-03 10:10:04, Feng Tang wrote:
> Add a dedicated core parameter 'panic_console_replay' for controlling
> console replay, and add note that 'panic_print' sysctl interface  will
> be obsoleted by 'panic_sys_info' and 'panic_console_replay'.  When it
> happens, the SYS_INFO_PANIC_CONSOLE_REPLAY can be removed as well.
> 
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -77,6 +78,13 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
>  EXPORT_SYMBOL(panic_notifier_list);
>  
>  #ifdef CONFIG_SYSCTL
> +static int sysctl_panic_print_handler(const struct ctl_table *table, int write,
> +			   void *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	pr_info_once("Kernel: 'panic_print' sysctl interface will be obsoleted by both 'panic_sys_info' and 'panic_console_replay'\n");
> +	return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
> +}

This warning is printed "only" when the value is accessed via the
procfs. It would be great to print it also when it is set
via the command line parameter.

It would require replacing

core_param(panic_print, panic_print, ulong, 0644);

with

core_param_cb(panic_print, &panic_print_ops, &panic_print, 0644);

Best Regards,
Petr