Re: [PATCH 03/10] perf tool: new iterfaces to read event from ring buffer

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Oct 10, 2017 at 03:36:28PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Oct 10, 2017 at 03:34:55PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Tue, Oct 10, 2017 at 06:28:18PM +0000, Liang, Kan escreveu:
> > > > Em Tue, Oct 10, 2017 at 10:20:16AM -0700, kan.liang@intel.com escreveu:
> > > > > From: Kan Liang <kan.liang@intel.com>
> > > > >
> > > > > The perf_evlist__mmap_read only support forward mode. It needs a
> > > > > common function to support both forward and backward mode.
> > > > 
> > > > > The perf_evlist__mmap_read_backward is buggy.
> > > > 
> > > > So, what is the bug? You state that it is buggy, but don't spell out the bug,
> > > > please do so.
> > > > 
> > > 
> > > union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
> > > {
> > > 	struct perf_mmap *md = &evlist->mmap[idx];  <--- it should be backward_mmap
> > > 
> > > > If it fixes an existing bug, then it should go separate from this patchkit, right?
> > > 
> > > There is no one use perf_evlist__mmap_read_backward. So it doesn't trigger any issue.
> > 
> > There is no one at the end of your patchkit? Or no user _right now_? If
> > there is a user now, lemme see... yeah, no user right now, so _that_ is
> > yet another bug, i.e. it should be used, no? If this is just a left
> > over, then we should just throw it away, now, its a cleanup.
> 
> Wang, can you take a look at these two issues? 

So it looks leftover that should've been removed by the following cset, right Wang?

- Arnaldo

commit a0c6f451f90204847ce5f91c3268d83a76bde1b6
Author: Wang Nan <wangnan0@huawei.com>
Date:   Thu Jul 14 08:34:41 2016 +0000

    perf evlist: Drop evlist->backward
    
    Now there's no real user of evlist->backward. Drop it. We are going to
    use evlist->backward_mmap as a container for backward ring buffer.