linux-kernel - Re: [BUG] perf annotate: broken in pipe mode

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Date:	Fri, 01 Feb 2013 17:04:03 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo\@elte.hu" <mingo@...e.hu>,
	"ak\@linux.intel.com" <ak@...ux.intel.com>
Subject: Re: [BUG] perf annotate: broken in pipe mode

Hi Stephane,

On Fri, 1 Feb 2013 00:51:51 +0100, Stephane Eranian wrote:
> Hi,
>
> Looks like perf annotate in pipe mode is totally broken nowadays.
> I tried this from tip.git:
>
> $ perf record -o - noploop 5 >perf.data
> $ perf annotate -i i < perf.data
> Core dump
>
> Callstack looks as follows:
> 0x000000000049f9e4 in add_hist_entry (hists=0x809708,
> entry=0x7fffffffde60, al=0x7fffffffdff0, period=1) at util/hist.c:297
> 297 while (*p != NULL) {
> :t
> [Current thread is 1 (Thread 0x7ffff7fc9980 (LWP 13292))]
> (gdb) bt
> #0  0x000000000049f9e4 in add_hist_entry (hists=0x809708,
> entry=0x7fffffffde60, al=0x7fffffffdff0, period=1) at util/hist.c:297
> #1  0x000000000049fcca in __hists__add_entry (self=0x809708,
> al=0x7fffffffdff0, sym_parent=0x0, period=1) at util/hist.c:395
> #2  0x00000000004171b0 in perf_evsel__add_sample (evsel=0x809660,
> sample=0x7fffffffe0e0, al=0x7fffffffdff0, ann=0x7fffffffe750) at
> builtin-annotate.c:65
> #3  0x0000000000417394 in process_sample_event (tool=0x7fffffffe750,
> event=0x80af70, sample=0x7fffffffe0e0, evsel=0x809660,
> machine=0x8093c8) at builtin-annotate.c:102
> #4  0x000000000048c56d in perf_session_deliver_event
> (session=0x8092e0, event=0x80af70, sample=0x7fffffffe0e0,
> tool=0x7fffffffe750, file_offset=11688)
>     at util/session.c:870
> #5  0x000000000048cb20 in perf_session__process_event
> (session=0x8092e0, event=0x80af70, tool=0x7fffffffe750,
> file_offset=11688) at util/session.c:986
> #6  0x000000000048cf75 in __perf_session__process_pipe_events
> (self=0x8092e0, tool=0x7fffffffe750) at util/session.c:1120
>
> Looks like the session->evlist is not properly initialized in pipe
> mode or that evsel->hists
> is bogus because it crashes due to evsel->hists->entries_in == NULL.
> Don't know how
> you can get there.
>
> Anybody has a clue?

After some study I think I managed to figure out the root cause.  The
patch follows..


---------8<---------------8<------------
>From a550d15f788397552b3fc04dbe4a089498288a05 Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung.kim@....com>
Date: Fri, 1 Feb 2013 16:51:45 +0900
Subject: [PATCH] perf annotate: Process synthetic events for pipe mode

Stephane reported that perf annotate in pipe mode is broken with NULL
evlist.  It's because we didn't process ATTR and EVENT_TYPE events in
annoate.  Since in pipe mode we cannot get the event info from the
header, it should be handled prior to processing sample events so that
the event and/or evlist are added to the session properly.

I'm not sure TRACING_DATA and BUILD_ID events should also be processed
but adding them will cause no harm I guess. :)

After adding needed callbacks, I realized symbol_conf.nr_events value
should be increased when processing new events/attrs otherwise it'd
get a zero division exception when calling symbol__alloc_hist().

Reported-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-annotate.c | 4 ++++
 tools/perf/util/header.c      | 1 +
 2 files changed, 5 insertions(+)

diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
index dc870cf31b79..5509cc37a829 100644
--- a/tools/perf/builtin-annotate.c
+++ b/tools/perf/builtin-annotate.c
@@ -254,6 +254,10 @@ int cmd_annotate(int argc, const char **argv, const char *prefix __maybe_unused)
 			.comm	= perf_event__process_comm,
 			.exit	= perf_event__process_exit,
 			.fork	= perf_event__process_fork,
+			.attr		 = perf_event__process_attr,
+			.event_type	 = perf_event__process_event_type,
+			.tracing_data	 = perf_event__process_tracing_data,
+			.build_id	 = perf_event__process_build_id,
 			.ordered_samples = true,
 			.ordering_requires_timestamps = true,
 		},
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 8022b5254f75..274ecd401d41 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2950,6 +2950,7 @@ int perf_event__process_attr(union perf_event *event,
 		return -ENOMEM;
 
 	perf_evlist__add(evlist, evsel);
+	symbol_conf.nr_events++;
 
 	ids = event->header.size;
 	ids -= (void *)&event->attr.id - (void *)event;
-- 
1.7.11.7

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