selftests: cgroup: Minor code reorganizations

No functional change intended, these small changes are merged into one
commit and they serve as a preparation for an upcoming new testcase.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

MAINTAINERS

@@ -5222,6 +5222,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git
 F:	Documentation/admin-guide/cgroup-v1/cpusets.rst
 F:	include/linux/cpuset.h
 F:	kernel/cgroup/cpuset.c
+F:	tools/testing/selftests/cgroup/test_cpuset_prs.sh
 
 CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)
 M:	Johannes Weiner <hannes@cmpxchg.org>

tools/testing/selftests/cgroup/cgroup_util.c

@@ -286,6 +286,8 @@ int cg_destroy(const char *cgroup)
 {
 	int ret;
 
+	if (!cgroup)
+		return 0;
 retry:
 	ret = rmdir(cgroup);
 	if (ret && errno == EBUSY) {

tools/testing/selftests/cgroup/cgroup_util.h

@@ -11,6 +11,8 @@
 #define USEC_PER_SEC	1000000L
 #define NSEC_PER_SEC	1000000000L
 
+#define TEST_UID	65534 /* usually nobody, any !root is fine */
+
 /*
  * Checks if two given values differ by less than err% of their sum.
  */

tools/testing/selftests/cgroup/test_core.c

@@ -683,7 +683,7 @@ static int test_cgcore_thread_migration(const char *root)
  */
 static int test_cgcore_lesser_euid_open(const char *root)
 {
-	const uid_t test_euid = 65534;	/* usually nobody, any !root is fine */
+	const uid_t test_euid = TEST_UID;
 	int ret = KSFT_FAIL;
 	char *cg_test_a = NULL, *cg_test_b = NULL;
 	char *cg_test_a_procs = NULL, *cg_test_b_procs = NULL;

tools/testing/selftests/cgroup/test_cpuset_prs.sh

@@ -10,7 +10,7 @@
 skip_test() {
 	echo "$1"
 	echo "Test SKIPPED"
-	exit 0
+	exit 4 # ksft_skip
 }
 
 [[ $(id -u) -eq 0 ]] || skip_test "Test must be run as root!"