[PATCH] perf trace: Segfault when trying to trace events by cgroup

[Stanislav Ivanichkin]

 # ./perf trace -e sched:sched_switch -G test -a sleep 1
 perf: Segmentation fault
 Obtained 11 stack frames.
 ./perf(sighandler_dump_stack+0x43) [0x55cfdc636db3]
 /lib/x86_64-linux-gnu/libc.so.6(+0x3efcf) [0x7fd23eecafcf]
 ./perf(parse_cgroups+0x36) [0x55cfdc673f36]
 ./perf(+0x3186ed) [0x55cfdc70d6ed]
 ./perf(parse_options_subcommand+0x629) [0x55cfdc70e999]
 ./perf(cmd_trace+0x9c2) [0x55cfdc5ad6d2]
 ./perf(+0x1e8ae0) [0x55cfdc5ddae0]
 ./perf(+0x1e8ded) [0x55cfdc5ddded]
 ./perf(main+0x370) [0x55cfdc556f00]
 /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe6) [0x7fd23eeadb96]
 ./perf(_start+0x29) [0x55cfdc557389]
 Segmentation fault

 It happens because "struct trace" in option->value is passed to
 parse_cgroups function instead of "struct evlist".

Signed-off-by: Stanislav Ivanichkin <sivanichkin@xxxxxxxxxxxxxx>
Reviewed-by: Dmitry Monakhov <dmtrmonakhov@xxxxxxxxxxxxxx>
---
 tools/perf/builtin-trace.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index bea461b6f937..cbc4de6840db 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -4651,9 +4651,12 @@ static int trace__parse_cgroups(const struct option *opt, const char *str, int u
 {
 	struct trace *trace = opt->value;
 
-	if (!list_empty(&trace->evlist->core.entries))
-		return parse_cgroups(opt, str, unset);
-
+	if (!list_empty(&trace->evlist->core.entries)) {
+		struct option o = OPT_CALLBACK('G', "cgroup", &trace->evlist,
+			"name", "monitor event in cgroup name only",
+			parse_cgroups);
+		return parse_cgroups(&o, str, unset);
+	}
 	trace->cgroup = evlist__findnew_cgroup(trace->evlist, str);
 
 	return 0;
-- 
2.17.1