linux-kernel - [PATCH] perf tools: Don't set cmdline_group

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Date:	Wed, 26 Aug 2015 08:32:29 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...hat.com>
CC:	<linux-kernel@...r.kernel.org>, Wang Nan <wangnan0@...wei.com>,
	"Alexei Starovoitov" <ast@...mgrid.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	"Zefan Li" <lizefan@...wei.com>, <pi3orama@....com>
Subject: [PATCH] perf tools: Don't set cmdline_group_boundary if no evsel is collected

If parse_events__scanner() collects no entry, perf_evlist__last(evlist)
is invalid. Then setting of cmdline_group_boundary touches invalid.

It could happend in currect BPF implementation. See [1]. Although it
can be fixed, for safety reason it whould be better to introduce this
check.

[1]: http://lkml.kernel.org/n/1436445342-1402-19-git-send-email-wangnan0@huawei.com

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Zefan Li <lizefan@...wei.com>
Cc: pi3orama@....com
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/parse-events.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index cce3e43..02609da 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1171,9 +1171,11 @@ int parse_events(struct perf_evlist *evlist, const char *str,
 
 		perf_evlist__splice_list_tail(evlist, &data.list, entries);
 		evlist->nr_groups += data.nr_groups;
-		last = perf_evlist__last(evlist);
-		last->cmdline_group_boundary = true;
 
+		if (entries > 0) {
+			last = perf_evlist__last(evlist);
+			last->cmdline_group_boundary = true;
+		}
 		return 0;
 	}
 
-- 
1.8.3.4

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