linux-kernel - Re: [PATCH 05/12] perf pmu: Fix pmu events parsing rule

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Date:   Thu, 3 May 2018 13:47:38 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 05/12] perf pmu: Fix pmu events parsing rule

On Thu, May 03, 2018 at 02:38:15PM +0300, Adrian Hunter wrote:
> On 03/05/18 13:37, Jiri Olsa wrote:
> > On Thu, May 03, 2018 at 11:25:16AM +0300, Adrian Hunter wrote:
> >> Hi
> >>
> >> This breaks Intel PT i.e.
> >>
> >> $ perf record -e intel_pt//u uname
> >> event syntax error: 'intel_pt//u'
> >>                              \___ parser error
> >> Run 'perf list' for a list of valid events
> >>
> >>  Usage: perf record [<options>] [<command>]
> >>     or: perf record [<options>] -- <command> [<options>]
> >>
> >>     -e, --event <event>   event selector. use 'perf list' to list available events
> >>
> >> See below for cause.
> >>
> >> On 25/04/18 19:00, Arnaldo Carvalho de Melo wrote:
> >>> From: Jiri Olsa <jolsa@...nel.org>
> >>>
> >>> Currently all the event parsing fails end up in the event_pmu rule, and
> >>> display misleading help like:
> >>>
> >>>   $ perf stat -e inst kill
> >>>   event syntax error: 'inst'
> >>>                        \___ Cannot find PMU `inst'. Missing kernel support?
> >>>   ...
> >>>
> >>> The reason is that the event_pmu is too strong and match also single
> >>> string. Changing it to force the '/' separators to be part of the rule,
> >>> and getting the proper error now:
> >>>
> >>>   $ perf stat -e inst kill
> >>>   event syntax error: 'inst'
> >>>                        \___ parser error
> >>>   Run 'perf list' for a list of valid events
> >>>   ...
> >>>
> >>> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> >>> Reported-by: Ingo Molnar <mingo@...nel.org>
> >>> Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >>> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> >>> Cc: David Ahern <dsahern@...il.com>
> >>> Cc: Namhyung Kim <namhyung@...nel.org>
> >>> Cc: Peter Zijlstra <peterz@...radead.org>
> >>> Link: http://lkml.kernel.org/r/20180423090823.32309-5-jolsa@kernel.org
> >>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >>> ---
> >>>  tools/perf/util/parse-events.y | 8 ++++----
> >>>  1 file changed, 4 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> >>> index 7afeb80cc39e..d14464c42714 100644
> >>> --- a/tools/perf/util/parse-events.y
> >>> +++ b/tools/perf/util/parse-events.y
> >>> @@ -224,15 +224,15 @@ event_def: event_pmu |
> >>>  	   event_bpf_file
> >>>  
> >>>  event_pmu:
> >>> -PE_NAME opt_event_config
> >>> +PE_NAME '/' event_config '/'
> >>
> >> These are not equivalent because opt_event_config allows '//'
> >> but event_config cannot be an empty string.
> > 
> > yep, overlooked this one, how about patch below
> 
> Seems to work but gives build warnings:
> 
> util/parse-events.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
> util/parse-events.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]

hm, I wonder why my bison was silent.. there's conflict
with opt_event_config reduction to empty, I'll resend

thanks,
jirka