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

On 2019/4/10 22:54, Andy Lutomirski wrote:

On Tue, Apr 9, 2019 at 8:40 PM Li, Aubrey [off-list ref] wrote:

quoted

On 2019/4/10 10:36, Li, Aubrey wrote:

quoted

On 2019/4/10 10:25, Andy Lutomirski wrote:

quoted

On Tue, Apr 9, 2019 at 7:20 PM Li, Aubrey [off-list ref] wrote:

quoted

On 2019/4/10 9:58, Andy Lutomirski wrote:

quoted

On Tue, Apr 9, 2019 at 6:55 PM Aubrey Li [off-list ref] wrote:

quoted

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 <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <redacted>
Cc: Tim Chen <redacted>
Cc: Dave Hansen <redacted>
Cc: Arjan van de Ven <redacted>
Cc: Linux API <redacted>
Cc: Alexey Dobriyan <redacted>
Cc: Andrew Morton <akpm@linux-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.

Thanks,
-Aubrey