linux-kernel - Re: [PATCH v3 3/3] reboot: refactor and comment the cpu selection code

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Date:   Thu, 5 Nov 2020 19:09:53 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Arnd Bergmann <arnd@...db.de>, Mike Rapoport <rppt@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Robin Holt <robinmholt@...il.com>,
        Fabian Frederick <fabf@...net.be>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 3/3] reboot: refactor and comment the cpu selection
 code

On Tue 2020-11-03 22:40:25, Matteo Croce wrote:
> From: Matteo Croce <mcroce@...rosoft.com>
> 
> Small improvements to the code, without changing the way it works:
> - use a local variable, to avoid a small time lapse where reboot_cpu
>   can have an invalid value
> - comment the code which is not easy to understand at a glance
> - merge two identical code blocks into one
> - replace pointer arithmetics with equivalent array syntax
> 
> Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
> ---
>  kernel/reboot.c | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index af6f23d8bea1..dd483bde932b 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -551,20 +551,24 @@ static int __init reboot_setup(char *str)
>  			break;
>  
>  		case 's':
> -			if (isdigit(*(str+1)))
> -				reboot_cpu = simple_strtoul(str+1, NULL, 0);
> -			else if (str[1] == 'm' && str[2] == 'p' &&
> -							isdigit(*(str+3)))
> -				reboot_cpu = simple_strtoul(str+3, NULL, 0);
> -			else
> +			/*
> +			 * reboot_cpu is s[mp]#### with #### being the processor
> +			 * to be used for rebooting. Skip 's' or 'smp' prefix.
> +			 */
> +			str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
> +
> +			if (isdigit(str[0])) {
> +				int cpu = simple_strtoul(str, NULL, 0);
> +
> +				if (cpu >= num_possible_cpus()) {
> +					pr_err("Ignoring the CPU number in reboot= option. "
> +					"CPU %d exceeds possible cpu number %d\n",

Same here. I am not sure if Andrew would like to get this on a single
line.

In both cases:

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr