linux-kernel - Re: [PATCH] s390/spinlock: Replace simple_strtoul with kstrtouint in spin_retry

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Message-Id: <2022390E-B83C-4087-99D0-596A198E337B@linux.dev>
Date: Thu, 18 Dec 2025 11:17:02 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Heiko Carstens <hca@...ux.ibm.com>,
 Vasily Gorbik <gor@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>,
 joel granados <joel.granados@...nel.org>,
 Juergen Christ <jchrist@...ux.ibm.com>,
 linux-s390@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/spinlock: Replace simple_strtoul with kstrtouint in
 spin_retry_setup

On 18. Dec 2025, at 08:59, Alexander Gordeev wrote:
> On Sat, Dec 13, 2025 at 01:32:44PM +0100, Thorsten Blum wrote:
>> Replace simple_strtoul() with the recommended kstrtouint() for parsing
>> the 'spin_retry=' boot parameter. Unlike simple_strtoul(), which returns
>> an unsigned long, kstrtouint() converts the string directly to an
>> unsigned integer.
>> 
>> Check the return value of kstrtouint() and reject invalid values. This
>> adds error handling while preserving existing behavior for valid values,
>> and removes use of the deprecated simple_strtoul() helper.
>> 
>> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
>> ---
>> arch/s390/lib/spinlock.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>> 
>> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
>> index 10db1e56a811..b4ca53356b96 100644
>> --- a/arch/s390/lib/spinlock.c
>> +++ b/arch/s390/lib/spinlock.c
>> @@ -34,8 +34,7 @@ early_initcall(spin_retry_init);
>>  */
>> static int __init spin_retry_setup(char *str)
>> {
>> -	spin_retry = simple_strtoul(str, &str, 0);
>> -	return 1;
>> +	return kstrtouint(str, 0, &spin_retry) == 0;
> 
> Why not to use kstrtouint() return value, like other parameters do?

Returning kstrtouint() directly would be wrong because kstrtouint()
returns 0 on success, but spin_retry_setup() is expected to return 1 on
success and 0 if the parameter couldn't be handled.

Thanks,
Thorsten