linux-kernel - Re: [PATCH] perf probe: Return errno when does not hit any event

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Date:   Thu, 16 Mar 2017 18:39:03 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>, guohanjun@...wei.com
Subject: Re: [PATCH] perf probe: Return errno when does not hit any event

On Tue, 14 Mar 2017 10:30:56 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Tue, Mar 14, 2017 at 09:19:47PM +0800, Kefeng Wang escreveu:
> > Hi all, any comments, thanks.
> 
> For 'perf probe' make sure Masami is in the CC list, adding him, Masami?

Thanks Arnaldo,

Hi Kefeng, I've made the error ignored by design, since user might pass
the wildcard pattern to perf probe -d just for making sure.

You can check the pattern hits any event by using perf-probe --list PATTERN.
Would you have any use case to check the result?

Thank you,

> 
> - Arnaldo
>  
> > On 2017/3/7 15:33, Kefeng Wang wrote:
> > > + Arnaldo Carvalho de Melo <acme@...nel.org>
> > > 
> > > On 2017/3/6 17:34, Kefeng Wang wrote:
> > >> On old perf, when using perf probe -d to delete an inexistent event,
> > >> it return errno, eg,
> > >>
> > >> -bash-4.3# perf probe -d xxx  || echo $?
> > >> Info: Event "*:xxx" does not exist.
> > >>   Error: Failed to delete events.
> > >> 255
> > >>
> > >> But now perf_del_probe_events() will always set ret = 0, different
> > >> from previous del_perf_probe_events(). After this, it return errno
> > >> again, eg,
> > >>
> > >> -bash-4.3# ./perf probe -d xxx  || echo $?
> > >>   Error: Failed to delete events.
> > >> 254
> > >>
> > >> And it is more appropriate to return -ENOENT instead of -EPERM.
> > >>
> > >> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> > >> ---
> > >>  tools/perf/builtin-probe.c | 3 ++-
> > >>  1 file changed, 2 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
> > >> index 1fcebc3..c46b41c 100644
> > >> --- a/tools/perf/builtin-probe.c
> > >> +++ b/tools/perf/builtin-probe.c
> > >> @@ -444,7 +444,8 @@ static int perf_del_probe_events(struct strfilter *filter)
> > >>  	if (ret == -ENOENT && ret2 == -ENOENT)
> > >>  		pr_debug("\"%s\" does not hit any event.\n", str);
> > >>  		/* Note that this is silently ignored */
> > >> -	ret = 0;
> > >> +	else
> > >> +		ret = 0;
> > >>  
> > >>  error:
> > >>  	if (kfd >= 0)
> > >>
> > > 
> > > 
> > > .
> > > 


-- 
Masami Hiramatsu <mhiramat@...nel.org>