Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v9 2/3] x86,/proc/pid/status: Add AVX-512 usage elapsed
 time
To:     Thomas Gleixner <tglx@linutronix.de>,
        Aubrey Li <aubrey.li@intel.com>
Cc:     mingo@redhat.com, peterz@infradead.org, hpa@zytor.com,
        ak@linux.intel.com, tim.c.chen@linux.intel.com,
        dave.hansen@intel.com, arjan@linux.intel.com,
        linux-kernel@vger.kernel.org
References: <20190211185931.4386-1-aubrey.li@intel.com>
 <20190211185931.4386-2-aubrey.li@intel.com>
 <alpine.DEB.2.21.1902120905420.1654@nanos.tec.linutronix.de>
 <efe3e5c9-c477-8a28-5489-c943fe63efaa@linux.intel.com>
From:   "Li, Aubrey" <aubrey.li@linux.intel.com>
Message-ID: <7fb97f08-daac-1dad-f51e-13fe6753832c@linux.intel.com>
Date:   Tue, 12 Feb 2019 17:49:56 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.1.1
MIME-Version: 1.0
In-Reply-To: <efe3e5c9-c477-8a28-5489-c943fe63efaa@linux.intel.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2019/2/12 17:14, 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?
> Like the following? arch_report_meminfo() is used in fs/proc/... as well.
> 
> $ find . -name *.h | xargs grep arch_report_meminfo
> ./arch/s390/include/asm/pgtable.h:void arch_report_meminfo(struct seq_file *m);
> ./arch/x86/include/asm/pgtable_types.h:extern void arch_report_meminfo(struct seq_file *m);
> ./arch/parisc/include/asm/pgtable.h:extern void arch_report_meminfo(struct seq_file *m);
> 

Actually both way exist in the current kernel,the reason I chose to put the prototype
into architecture header file is that I found some architectures rename the function
name by a micro definition while others use prototype. See below:

$ find . -name *.h | xargs grep arch_irq_stat
./arch/arm64/include/asm/hardirq.h:#define arch_irq_stat_cpu	smp_irq_stat_cpu
./arch/arm/include/asm/hardirq.h:#define arch_irq_stat_cpu	smp_irq_stat_cpu
./arch/x86/include/asm/hardirq.h:extern u64 arch_irq_stat_cpu(unsigned int cpu);

This looks more flexible than it in the common header file.

Anyway, putting the prototype into the common header file like include/linux/proc_fs.h
is also acceptable to me if you persist, please just let me know, :)

Thanks,
-Aubrey