linux-kernel - Re: [PATCH v9 2/3] x86,/proc/pid/status: Add AVX-512 usage elapsed time

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Message-ID: <8434e9a2-6173-4e2b-f635-51a1683bcd25@linux.intel.com>
Date:   Tue, 12 Feb 2019 20:02:34 +0800
From:   "Li, Aubrey" <aubrey.li@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Aubrey Li <aubrey.li@...el.com>, mingo@...hat.com,
        peterz@...radead.org, hpa@...or.com, ak@...ux.intel.com,
        tim.c.chen@...ux.intel.com, dave.hansen@...el.com,
        arjan@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 2/3] x86,/proc/pid/status: Add AVX-512 usage elapsed
 time

On 2019/2/12 19:55, Thomas Gleixner wrote:
> On Tue, 12 Feb 2019, Li, Aubrey wrote:
>> On 2019/2/12 19:19, Thomas Gleixner wrote:
>>> On Tue, 12 Feb 2019, Li, Aubrey wrote:
>>>> On 2019/2/12 16:22, Thomas Gleixner wrote:
>>>>> On Tue, 12 Feb 2019, Aubrey Li wrote:
>>>>>> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
>>>>>> index d53c54b842da..60ee932070fe 100644
>>>>>> --- a/arch/x86/include/asm/processor.h
>>>>>> +++ b/arch/x86/include/asm/processor.h
>>>>>> @@ -996,5 +996,7 @@ enum l1tf_mitigations {
>>>>>>  };
>>>>>>  
>>>>>>  extern enum l1tf_mitigations l1tf_mitigation;
>>>>>> +/* Add support for architecture specific output in /proc/pid/status */
>>>>>> +extern void arch_proc_pid_status(struct seq_file *m, struct task_struct *task);
>>>>>
>>>>> Sigh. This is absolutely the wrong place. The weak function is declared and
>>>>> used in fs/proc/... So the prototype wants to be in a header which is
>>>>> included from there independent of x86...
>>>>
>>>> Can the prototype be in the architecture header if they want to call the
>>>> function?
>>>
>>> Basic C programming course:
>>>
>>>  The prototype must be available before the declaration of the global
>>>  function.
>>>
>>> fs/proc/array.c:404:13: warning: no previous prototype for ‘arch_proc_pid_status’ [-Wmissing-prototypes]
>>>  void __weak arch_proc_pid_status(struct seq_file *m, struct task_struct *task)
>>>
>>> Oh well....
>>
>> Is this because patch 1/3 applied alone? If the whole patch set are applied,
>> the prototype is included in <asm/processor.h>, which is at the beginning of
>> array.c file, so it is available before the declaration.
> 
> 1) Each patch has to be correct stand alone
> 
> 2) This file is compiled for every architecture the kernel supports and how
>    many of them are including arch/x86/include/asm/processor.h ?
> 
>    There is a world outside x86 and it's rather large.

Got it, thanks!

> 
> Thanks,
> 
> 	tglx
>