linux-kernel - [PATCH] perf report: Fix a bug on "--call-graph none" option

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Date:	Wed, 30 Sep 2015 13:34:00 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Kan Liang <kan.liang@...el.com>
Subject: [PATCH] perf report: Fix a bug on "--call-graph none" option

The patch f9db0d0f1b2c ("perf callchain: Allow disabling call graphs
per event") added an ability to enable/disable callchain recording per
event.  But it had a problem when the enablement setting is changed at
'perf report' time using -g/--call-graph option.

For example, the following scenario will get a segfault.

  $ perf record -ag sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.500 MB perf.data (2555 samples) ]

  $ perf report -g none
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x53a98a]
  /usr/lib/libc.so.6(+0x335af)[0x7f4e91df95af]

This is because callchain_param.sort() callback was not set but it
tried to call the function as it had the PERF_SAMPLE_CALLCHAIN bit.

Cc: Kan Liang <kan.liang@...el.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/hist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index b3567a25f0c4..99b8e14ce010 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1149,7 +1149,7 @@ void hists__output_resort(struct hists *hists, struct ui_progress *prog)
 	struct perf_evsel *evsel = hists_to_evsel(hists);
 	bool use_callchain;
 
-	if (evsel && !symbol_conf.show_ref_callgraph)
+	if (evsel && symbol_conf.use_callchain && !symbol_conf.show_ref_callgraph)
 		use_callchain = evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN;
 	else
 		use_callchain = symbol_conf.use_callchain;
-- 
2.5.0

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