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 07:54:31 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     "Li, Aubrey" <aubrey.li@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        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 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.