linux-kernel - Re: [PATCH v6 2/3] perf tools: Add lexical definition of event name

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Date:   Tue, 16 Feb 2021 12:13:23 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Shunsuke Nakamura <nakamura.shun@...fujitsu.com>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 2/3] perf tools: Add lexical definition of event name

On Tue, Feb 16, 2021 at 05:23:18PM +0900, Namhyung Kim wrote:
> On Mon, Feb 15, 2021 at 9:34 PM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Fri, Feb 12, 2021 at 06:03:17PM +0900, Shunsuke Nakamura wrote:
> > > Add the lexical definition of event name so that the numbers are recognizable.
> > >
> > > A64FX defines an event name that starts with a number.
> > >  - 0inst_commit
> > >  - 1inst_commit
> > >  - 2inst_commit
> > >  - 3inst_commit
> > >  - 4inst_commit
> > >
> > > Signed-off-by: Shunsuke Nakamura <nakamura.shun@...itsu.com>
> > > ---
> > >  tools/perf/util/parse-events.l | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> > > index 0b36285a9435..33f627187415 100644
> > > --- a/tools/perf/util/parse-events.l
> > > +++ b/tools/perf/util/parse-events.l
> > > @@ -205,7 +205,7 @@ bpf_source        [^,{}]+\.c[a-zA-Z0-9._]*
> > >  num_dec              [0-9]+
> > >  num_hex              0x[a-fA-F0-9]+
> > >  num_raw_hex  [a-fA-F0-9]+
> > > -name         [a-zA-Z_*?\[\]][a-zA-Z0-9_*?.\[\]]*
> > > +name         [a-zA-Z0-9_*?\[\]][a-zA-Z0-9_*?.\[\]]*
> >
> > I can't see anything broken because of this change,
> > also numbers are defined few lines before so we should
> > be fine
> 
> But this change makes the syntax ambiguous with numbers
> and names. I don't think it's a good idea.

I'll check again, but we already have hex numbers above
which could easily clash, but the syntax context makes
this work.. tests should help to clear this up

> 
> Is it possible to change the event names not having numbers
> at the beginning like inst_commit0, inst_commit1 and so on?

that'd be of course much better

thanks,
jirka

> 
> Thanks,
> Namhyung
>