linux-kernel - Re: [PATCH v7 0/6] tracing: More synthetic event error fixes

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Date:   Tue, 09 Feb 2021 16:58:12 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     axelrasmussen@...gle.com, mhiramat@...nel.org,
        dan.carpenter@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/6] tracing: More synthetic event error fixes

Hi Steve,

On Tue, 2021-02-09 at 16:09 -0500, Steven Rostedt wrote:
> On Mon,  1 Feb 2021 13:48:10 -0600
> Tom Zanussi <zanussi@...nel.org> wrote:
> 
> > Hi,
> > 
> > This is v7 of the synthetic event error fix patchset.  This version
> > addresses the comments from v6:
> > 
> >   - moved check_command() from '[PATCH v6 3/6] tracing: Update
> > synth
> >     command errors' to '[PATCH v6 2/6] tracing: Rework synthetic
> > event
> >     command parsing'.
> > 
> >   - in __create_synth_event(), moved mutex_lock(&event_mutex) after
> >     is_good_name() check and changed related error handling.
> > 
> >   - simplified check_command() a bit by calling argv_free() sooner
> > as
> >     suggested by Steve.
> > 
> >   - added Steve's comment about check_field_version() into that
> >     function and added additional comments to the caller.
> > 
> 
> After applying these, the following test fails:
> 
>  test.d/trigger/inter-event/trigger-synthetic_event_syntax_errors.tc
> 

Did you apply '[PATCH v7 5/6] selftests/ftrace: Update synthetic event
syntax errors' before you ran the test?  It actually removes the test
that failed.  Here's what I get with all patches applied:

  # ./ftracetest test.d/trigger/inter-event/
=== Ftrace unit tests ===
[1] event trigger - test inter-event histogram trigger expected fail
actions	[XFAIL]
[2] event trigger - test field variable support	[PASS]
[3] event trigger - test inter-event combined histogram trigger	[PASS]
[4] event trigger - test multiple actions on hist trigger	[PASS]
[5] event trigger - test inter-event histogram trigger onchange action	
[PASS]
[6] event trigger - test inter-event histogram trigger onmatch action	
[PASS]
[7] event trigger - test inter-event histogram trigger onmatch-onmax
action	[PASS]
[8] event trigger - test inter-event histogram trigger onmax action	
[PASS]
[9] event trigger - test inter-event histogram trigger snapshot action	
[PASS]
[10] event trigger - test synthetic event create remove	[PASS]
[11] event trigger - test inter-event histogram trigger trace action
with dynamic string param	[PASS]
[12] event trigger - test synthetic_events syntax parser errors	[PASS]
[13] event trigger - test synthetic_events syntax parser	[PASS]
[14] event trigger - test inter-event histogram trigger trace action	
[PASS]


# of passed:  13
# of failed:  0
# of unresolved:  0
# of untested:  0
# of unsupported:  0
# of xfailed:  1
# of undefined(test bug):  0

> It appears that:
> 
>   echo 'myevent char str[];; int v' > synthetic_events
> 
> doesn't error after these changes.
> 

Right, it shouldn't fail any more - that was one of the reasons for
reworking the parser, so things like that wouldn't fail.

My assumption, and the reason for adding '[PATCH v7 4/6] tracing: Add a
backward-compatibility check for synthetic event creation', was that we
didn't want previously-working things to suddenly start failing after
the rework, but not that things that used to fail would continue to 
backwards-compatibly fail.

Tom

> -- Steve