Re: [PATCH 1/2] trace-cmd: remove parsing_failures APIs from libtraceevent

[Tzvetomir Stoyanov <tstoyanov@vmware.com>]

On Wed, Apr 17, 2019 at 4:19 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 17 Apr 2019 09:10:26 +0000
> Tzvetomir Stoyanov <tstoyanov@vmware.com> wrote:
>
> Let's not add this. Instead add a "parsing_failures" to the
> > > tracecmd_input handle, and add:
> > >
> > > int tracecmd_get_parsing_failures(struct tracecmd_input *handle)
> > > {
> > >         return handle->parsing_failures;
> > > }
> > >
> > I hesitated if to add new API, or use additional parameter to the
> > existing functions.
> > The reason for this change is to remove "parsing_failures" from
> > traceevent library,
> > that's why I decided not to move it to trace-cmd library. Using new
> > library API is nicer,
> > I can reimplement it in this way, but we may have the same concerns
> > when trace-cmd
> > library comes out.
> >
>
> That's a valid concern, but there is a difference between the
> libtraceevent and libftrace (or whatever we decide to name it ;-)
>
> The trace-cmd code will be a higher level library on top of
> libtraceevent. The main difference is that the trace-cmd code has
> algorithms that deal with the counter but the tep code did not. We
> incorrectly added that counter to the tep code only because a higher
> layer needed it. The tep layer did not understand the context of that
> counter.
>
> My concern with the counter in the tep code was that it was at the
> wrong level. That is, the tep code had no processing for that counter.
> To put it a different way, the tep code did not understand the context
> of the counter. We had to add API to set and reset that counter, which
> was a clear indication that the tep library shouldn't be the one to
> store it.
>
> Now at the trace-cmd code level (libftrace), it most definitely
> understands the context of that counter. Thus the counter should be
> stored at that level. We didn't need to add APIs to the trace-cmd code
> to reset that counter, or increment it. Because the trace-cmd library
> knows the context of the counter. That's how one knows if the library
> should store the counter or not.
>
> Let's make the parsing_failures part of the tracecmd_input handler and
> it will simplify this patch quite a bit.
>
> Does that make sense?
>

Yes, it makes sense. I'll prepare the next version of the patch.

> -- Steve
>
>
> > > > +{
> > > > +     return _tracecmd_read_headers(handle, parsing_failures);
> > > > +}
> > > > +
> > >
> > > [..]
> > >
> > > > diff --git a/tracecmd/trace-read.c b/tracecmd/trace-read.c
> > > > index 52fa1bd..fe116cc 100644
> > > > --- a/tracecmd/trace-read.c
> > > > +++ b/tracecmd/trace-read.c
> > > > @@ -1417,6 +1417,7 @@ void trace_report (int argc, char **argv)
> > > >       unsigned long long tsoffset = 0;
> > > >       unsigned long long ts2secs = 0;
> > > >       unsigned long long ts2sc;
> > > > +     int parsing_failures;
> > > >       int show_stat = 0;
> > > >       int show_funcs = 0;
> > > >       int show_endian = 0;
> > > > @@ -1714,10 +1715,10 @@ void trace_report (int argc, char **argv)
> > > >                       tracecmd_print_events(handle, print_event);
> > > >                       return;
> > > >               }
> > > > -
> > > > -             ret = tracecmd_read_headers(handle);
> > > > +             parsing_failures = 0;
> > > > +             ret = tracecmd_read_headers_failures(handle, &parsing_failures);
> > >
> > > Here we should do:
> > >
> > >                 ret = tracecmd_read_headers(handle);
> > >
> > > >               if (check_event_parsing) {
> > > > -                     if (ret || tep_get_parsing_failures(pevent))
> > >
> > >                         if (ret || tracecmd_get_parsing_failures(handle))
> > >
> > > -- Steve
> > >
> > > > +                     if (ret || parsing_failures)
> > > >                               exit(EINVAL);
> > > >                       else
> > > >                               exit(0);
> > >
> >
> >
>


-- 

Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center