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Message-ID: <70616a41-fe5f-aff8-2aca-4cb827e8553f@redhat.com>
Date:   Thu, 12 May 2022 15:40:54 +0200
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Subject: Re: [pdx86-platform-drivers-x86:review-hans 46/59]
 kernel/stop_machine.c:638:35: error: call to undeclared function
 'cpu_smt_mask'; ISO C99 and later do not support implicit function
 declarations
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To:     Thomas Gleixner <tglx@linutronix.de>,
        kernel test robot <lkp@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     llvm@lists.linux.dev, kbuild-all@lists.01.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-kernel@vger.kernel.org, Tony Luck <tony.luck@intel.com>
References: <202205120904.Gr9HEY5E-lkp@intel.com> <87zgjnw1bg.ffs@tglx>
 <ce8e9601-f514-5227-f9f7-87594218f95f@redhat.com> <87r14zvuxp.ffs@tglx>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <87r14zvuxp.ffs@tglx>
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Hi,

On 5/12/22 13:42, Thomas Gleixner wrote:
> On Thu, May 12 2022 at 11:53, Hans de Goede wrote:
>> On 5/12/22 11:24, Thomas Gleixner wrote:
>>> On Thu, May 12 2022 at 09:29, kernel test robot wrote:
>>>>>> kernel/stop_machine.c:638:35: error: call to undeclared function 'cpu_smt_mask'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>>>>            const struct cpumask *smt_mask = cpu_smt_mask(cpu);
>>>
>>> This warning with W=1 is not the worst of the problems.
>>>
>>> The build will simply fail for CONFIG_SMP=y && CONFIG_SCHED_SMT=n
>>> because cpu_smt_mask() cannot be resolved.
>>>
>>> The other issue is CONFIG_SMP=n. This will fail to build the IFS driver
>>> because stop_core_cpuslocked() is not available for SMP=n.
>>
>> The IFS Kconfig already depends on SMP :
>>
>> config INTEL_IFS
>>         tristate "Intel In Field Scan"
>>         depends on X86 && 64BIT && SMP
>>         select INTEL_IFS_DEVICE
>>         help
>>           Enable ...
>>
>>
>> So I don't think we need the non-SMP implementation inside
>> include/linux/stop_machine.h, we only need the #ifdef you
>> suggest in kernel/stop_machine.c  ?
> 
> For the case at hand that's sufficient.
> 
>> I think it is best to just squash this into the original
>> patch, do you agree ?
> 
> Yes.

Ok, I've squashed the #ifdef into kernel/stop_machine.c and done
a forced push. Lets hope that the kernel test robot (lkp) does
not find anything else.

Regards,

Hans