Re: [PATCH v3 4/8] cgroup: Remove CGROUP_BUILTIN_SUBSYS_COUNT

@@ -4502,10 +4507,13 @@ int __init cgroup_init_early(void)
 	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
 		INIT_HLIST_HEAD(&css_set_table[i]);
 
-	/* at bootup time, we don't worry about modular subsystems */
-	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 		struct cgroup_subsys *ss = subsys[i];
 
+		/* at bootup time, we don't worry about modular subsystems */
+		if (!ss || (ss && ss->module))
+			continue;
+

@@ -4538,9 +4546,12 @@ int __init cgroup_init(void)
 	if (err)
 		return err;
 
-	/* at bootup time, we don't worry about modular subsystems */
-	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 		struct cgroup_subsys *ss = subsys[i];
+
+		/* at bootup time, we don't worry about modular subsystems */
+		if (!ss || (ss && ss->module))
+			continue;

@@ -4735,13 +4746,16 @@ void cgroup_fork_callbacks(struct task_struct *child)
 {
 	if (need_forkexit_callback) {
 		int i;
-		/*
-		 * forkexit callbacks are only supported for builtin
-		 * subsystems, and the builtin section of the subsys array is
-		 * immutable, so we don't need to lock the subsys array here.
-		 */
-		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 			struct cgroup_subsys *ss = subsys[i];
+
+			/*
+			 * forkexit callbacks are only supported for
+			 * builtin subsystems.
+			 */
+			if (!ss || (ss && ss->module))
+				continue;
+

@@ -4846,12 +4860,13 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 	tsk->cgroups = &init_css_set;
 
 	if (run_callbacks && need_forkexit_callback) {
-		/*
-		 * modular subsystems can't use callbacks, so no need to lock
-		 * the subsys array
-		 */
-		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 			struct cgroup_subsys *ss = subsys[i];
+
+			/* modular subsystems can't use callbacks */
+			if (!ss || (ss && ss->module))
+				continue;
+

@@ -5037,13 +5052,17 @@ static int __init cgroup_disable(char *str)
 	while ((token = strsep(&str, ",")) != NULL) {
 		if (!*token)
 			continue;
-		/*
-		 * cgroup_disable, being at boot time, can't know about module
-		 * subsystems, so we don't worry about them.
-		 */
-		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 			struct cgroup_subsys *ss = subsys[i];
 
+			/*
+			 * cgroup_disable, being at boot time, can't
+			 * know about module subsystems, so we don't
+			 * worry about them.
+			 */
+			if (!ss || (ss && ss->module))
+				continue;
+