Date:   Fri, 12 Apr 2019 08:55:19 +0800
From:   "Li, Aubrey" <aubrey.li@...ux.intel.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, aubrey.li@...el.com,
        Linux API <linux-api@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 1/3] /proc/pid/status: Add support for architecture
 specific output

On 2019/4/11 9:02, Li, Aubrey wrote:
> On 2019/4/10 22:54, Andy Lutomirski wrote:
>> On Tue, Apr 9, 2019 at 8:40 PM Li, Aubrey <aubrey.li@...ux.intel.com> wrote:
>>>
>>> On 2019/4/10 10:36, Li, Aubrey wrote:
>>>> On 2019/4/10 10:25, Andy Lutomirski wrote:
>>>>> On Tue, Apr 9, 2019 at 7:20 PM Li, Aubrey <aubrey.li@...ux.intel.com> wrote:
>>>>>>
>>>>>> On 2019/4/10 9:58, Andy Lutomirski wrote:
>>>>>>> On Tue, Apr 9, 2019 at 6:55 PM Aubrey Li <aubrey.li@...ux.intel.com> wrote:
>>>>>>>>
>>>>>>>> The architecture specific information of the running processes could
>>>>>>>> be useful to the userland. Add support to examine process architecture
>>>>>>>> specific information externally.
>>>>>>>>
>>>>>>>> Signed-off-by: Aubrey Li <aubrey.li@...ux.intel.com>
>>>>>>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>>>>>>> Cc: Andi Kleen <ak@...ux.intel.com>
>>>>>>>> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
>>>>>>>> Cc: Dave Hansen <dave.hansen@...el.com>
>>>>>>>> Cc: Arjan van de Ven <arjan@...ux.intel.com>
>>>>>>>> Cc: Linux API <linux-api@...r.kernel.org>
>>>>>>>> Cc: Alexey Dobriyan <adobriyan@...il.com>
>>>>>>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>>>>>>> ---
>>>>>>>>  fs/proc/array.c         | 5 +++++
>>>>>>>>  include/linux/proc_fs.h | 2 ++
>>>>>>>>  2 files changed, 7 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/fs/proc/array.c b/fs/proc/array.c
>>>>>>>> index 2edbb657f859..331592a61718 100644
>>>>>>>> --- a/fs/proc/array.c
>>>>>>>> +++ b/fs/proc/array.c
>>>>>>>> @@ -401,6 +401,10 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
>>>>>>>>         seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
>>>>>>>>  }
>>>>>>>>
>>>>>>>> +void __weak arch_proc_pid_status(struct seq_file *m, struct task_struct *task)
>>>>>>>> +{
>>>>>>>> +}
>>>>>>>
>>>>>>> This pointlessly bloats other architectures.  Do this instead in an
>>>>>>> appropriate header:
>>>>>>>
>>>>>>> #ifndef arch_proc_pid_status
>>>>>>> static inline void arch_proc_pid_status(...)
>>>>>>> {
>>>>>>> }
>>>>>>> #endif
>>>>>>>
>>>>>>
>>>>>> I saw a bunch of similar weak functions, is it not acceptable?
>>>>>>
>>>>>> fs/proc$ grep weak *.c
>>>>>> cpuinfo.c:__weak void arch_freq_prepare_all(void)
>>>>>> meminfo.c:void __attribute__((weak)) arch_report_meminfo(struct seq_file *m)
>>>>>> vmcore.c:int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
>>>>>> vmcore.c:void __weak elfcorehdr_free(unsigned long long addr)
>>>>>> vmcore.c:ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>>>>>> vmcore.c:ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
>>>>>> vmcore.c:int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
>>>>>> vmcore.c:ssize_t __weak
>>>>>
>>>>> I think they're acceptable, but I don't personally like them.
>>>>>
>>>>
>>>> okay, let me try to see if I can refine it in an appropriate way.
>>>
>>> Hi Andy,
>>>
>>> Is this what you want?
>>>
>>> Thanks,
>>> -Aubrey
>>>
>>> ====================================================================
>>> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
>>> index 2bb3a648fc12..82d77d3aefff 100644
>>> --- a/arch/x86/include/asm/processor.h
>>> +++ b/arch/x86/include/asm/processor.h
>>> @@ -990,5 +990,8 @@ enum l1tf_mitigations {
>>>  };
>>>
>>>  extern enum l1tf_mitigations l1tf_mitigation;
>>> +/* Add support for architecture specific output in /proc/pid/status */
>>> +void arch_proc_pid_status(struct seq_file *m, struct task_struct *task);
>>> +#define arch_proc_pid_status arch_proc_pid_status
>>>
>>>  #endif /* _ASM_X86_PROCESSOR_H */
>>> diff --git a/fs/proc/array.c b/fs/proc/array.c
>>> index 2edbb657f859..fd65a6ba2864 100644
>>> --- a/fs/proc/array.c
>>> +++ b/fs/proc/array.c
>>> @@ -401,6 +401,11 @@ static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
>>>         seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
>>>  }
>>>
>>> +/* Add support for architecture specific output in /proc/pid/status */
>>> +#ifndef arch_proc_pid_status
>>> +#define arch_proc_pid_status(m, task)
>>> +#endif
>>> +
>>>  int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
>>>                         struct pid *pid, struct task_struct *task)
>>>  {
>>> @@ -424,6 +429,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
>>>         task_cpus_allowed(m, task);
>>>         cpuset_task_status_allowed(m, task);
>>>         task_context_switch_counts(m, task);
>>> +       arch_proc_pid_status(m, task);
>>>         return 0;
>>>  }
>>>
>>
>> Yes.  But I still think it would be nicer to separate the arch stuff
>> into its own file.  Others might reasonably disagree with me.
>>
> I like arch_status, I proposed but no other arch shows interesting in it.
> 
> I think the problem is similar for x86_status, it does not make sense for
> those x86 platform without AVX512 to have an empty arch file. I personally
> don't like [arch]_status because the code may become unclean if more arches
> added in future.
> 
> Maybe it's too early to have a separated arch staff file for now.

Hi Andy,

Is it acceptable to you if I make the above change and post v15?

Thanks,
-Aubrey

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