linux-kernel - Re: [PATCH v14 1/3] /proc/pid/status: Add support for architecture specific output

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Date:   Wed, 10 Apr 2019 10:20:28 +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 2019/4/10 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

> Or add /proc/PID/x86_status, which sounds better in most respects to me.
> 

I didn't figure out how to make /proc/PID/x86_status invisible to other
architectures in an appropriate way, do you have any suggestions?

Thanks,
-Aubrey