linux-kernel - Re: [PATCH v5 06/17] sched/debug: Output SD flag names rather than their values

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Date:   Thu, 13 Aug 2020 14:13:10 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     kernel test robot <lkp@...el.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kbuild-all@...ts.01.org,
        mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH v5 06/17] sched/debug: Output SD flag names rather than
 their values

On 13/08/2020 13:02, Luc Van Oostenryck wrote:
> On Wed, Aug 12, 2020 at 07:51:08PM +0100, Valentin Schneider wrote:
>> On 12/08/20 17:35, kernel test robot wrote:
>>
>>> config: i386-randconfig-s001-20200811 (attached as .config)
>>> reproduce:
>>>         # sparse version: v0.6.2-168-g9554805c-dirty
>>>         make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=i386
>>>
>>>>> kernel/sched/debug.c:279:17: sparse: sparse: non size-preserving pointer to integer cast
>>>>> kernel/sched/debug.c:279:17: sparse: sparse: non size-preserving integer to pointer cast
>>>
>>>  > 279		tmp += *ppos;
>>
>> I pretty much copied kernel/sysctl.c::_proc_do_string() and I think that's
>> exactly the same types here: char* buffer incremented by loff_t offset. It
>> does look fine to me, but I can't really parse that warning.
> 
> The warnings mean that there is a cast from a pointer to an integer with
> a size other than the size of a pointer and the other way around.
> 
> I's indeed the case here, on i386, where pointers are 32-bit and loff_t
> is 64-bit. But yes, I agree:
> 1) these messages are far from clear
> 2) these casts are internal and are probably not appropriate here.
> 
> I'll look later what can be done at sparse level.
> 

Thanks!

> Regards,
> -- Luc
>