perf cgroup: Introduce cgroup__get()

The refcount operation counterpart to cgroup__put(), use it when reusing
a cgroup.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-14ynvrl7y2cz8gyuy5q5v41g@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/cgroup.c

@@ -99,15 +99,12 @@ static int add_cgroup(struct perf_evlist *evlist, char *str)
 	 * check if cgrp is already defined, if so we reuse it
 	 */
 	evlist__for_each_entry(evlist, counter) {
-		cgrp = counter->cgrp;
-		if (!cgrp)
+		if (!counter->cgrp)
 			continue;
-		if (!strcmp(cgrp->name, str)) {
-			refcount_inc(&cgrp->refcnt);
+		if (!strcmp(counter->cgrp->name, str)) {
+			cgrp = cgroup__get(counter->cgrp);
 			break;
 		}
-
-		cgrp = NULL;
 	}
 
 	if (!cgrp) {
@@ -157,6 +154,13 @@ void cgroup__put(struct cgroup *cgrp)
 	}
 }
 
+struct cgroup *cgroup__get(struct cgroup *cgroup)
+{
+       if (cgroup)
+		refcount_inc(&cgroup->refcnt);
+       return cgroup;
+}
+
 int parse_cgroups(const struct option *opt, const char *str,
 		  int unset __maybe_unused)
 {

tools/perf/util/cgroup.h

@@ -15,6 +15,7 @@ struct cgroup {
 
 extern int nr_cgroups; /* number of explicit cgroups defined */
 
+struct cgroup *cgroup__get(struct cgroup *cgroup);
 void cgroup__put(struct cgroup *cgroup);
 
 int parse_cgroups(const struct option *opt, const char *str, int unset);