perf cgroup: Add evlist__findnew_cgroup()

Similar to machine__findnew_thread(), etc, i.e. try to find, get a
refcount if found and return it, otherwise return a new cgroup object.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/cgroup.c

···
 	return NULL;
 }
 
+struct cgroup *evlist__findnew_cgroup(struct perf_evlist *evlist, char *name)
+{
+	struct cgroup *cgroup = evlist__find_cgroup(evlist, name);
+
+	return cgroup ?: cgroup__new(name);
+}
+
 static int add_cgroup(struct perf_evlist *evlist, char *str)
 {
 	struct perf_evsel *counter;
-	struct cgroup *cgrp = evlist__find_cgroup(evlist, str);
+	struct cgroup *cgrp = evlist__findnew_cgroup(evlist, str);
 	int n;
 
-	if (!cgrp) {
-		cgrp = cgroup__new(str);
-		if (!cgrp)
-			return -1;
-	}
-
+	if (!cgrp)
+		return -1;
 	/*
 	 * find corresponding event
 	 * if add cgroup N, then need to find event N

tools/perf/util/cgroup.h

···
 struct cgroup *cgroup__get(struct cgroup *cgroup);
 void cgroup__put(struct cgroup *cgroup);
 
+struct perf_evlist;
+
+struct cgroup *evlist__findnew_cgroup(struct perf_evlist *evlist, char *name);
+
 int parse_cgroups(const struct option *opt, const char *str, int unset);
 
 #endif /* __CGROUP_H__ */