Re: [PATCH] trace/ring_buffer: remove unused arguments

[chensong]

Hi,

On 2022/10/20 下午10:15, Steven Rostedt wrote:
> On Thu, 20 Oct 2022 22:06:51 +0800
> Song Chen <chensong_2000@xxxxxx> wrote:
>
> > As a argument, event has nothing to do with either
> > ring_buffer_unlock_commit or rb_commit and cleaning
> > it up has no side effect.
>
> OK, so this is because of a389d86f7fd0 ("ring-buffer: Have nested events
> still record running time stamp") which removed the usage of event in rb_commit():
>
>   static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
>                        struct ring_buffer_event *event)
>   {
>          local_inc(&cpu_buffer->entries);
> -       rb_update_write_stamp(cpu_buffer, event);
>          rb_end_commit(cpu_buffer);
>   }
>
>
> I guess this doesn't hurt.
>
> -- Steve

I was reading __kprobe_trace_func, store_trace_args stores args in 
fbuffer.entry,which is event->array, but at the end, rb_commit uses 
fbuffer.buffer instead of event.

Then i thought, if it's useless, why not just clean it up.

Song

> > Signed-off-by: Song Chen <chensong_2000@xxxxxx>
> > ---
> >   include/linux/ring_buffer.h          |  3 +--
> >   kernel/trace/ring_buffer.c           | 12 +++++-------
> >   kernel/trace/ring_buffer_benchmark.c |  2 +-
> >   kernel/trace/trace.c                 |  2 +-
> >   4 files changed, 8 insertions(+), 11 deletions(-)