diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 145901f..1916cdb 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -48,7 +48,7 @@
 #define SUBSYS(_x) _x ## _subsys_id,
 enum cgroup_subsys_id {
 #include <linux/cgroup_subsys.h>
-	CGROUP_BUILTIN_SUBSYS_COUNT
+	__CGROUP_TEMPORARY_PLACEHOLDER
 };
 #undef SUBSYS
 /*
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ced292d..1b18090 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -88,7 +88,7 @@
 
 /*
  * Generate an array of cgroup subsystem pointers. At boot time, this is
- * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
+ * populated with the built in subsystems, and modular subsystems are
  * registered after that. The mutable section of this array is protected by
  * cgroup_mutex.
  */
@@ -1321,7 +1321,7 @@
 	 * take duplicate reference counts on a subsystem that's already used,
 	 * but rebind_subsystems handles this case.
 	 */
-	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
+	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 		unsigned long bit = 1UL << i;
 
 		if (!(bit & opts->subsys_mask))
@@ -1337,7 +1337,7 @@
 		 * raced with a module_delete call, and to the user this is
 		 * essentially a "subsystem doesn't exist" case.
 		 */
-		for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
+		for (i--; i >= 0; i--) {
 			/* drop refcounts only on the ones we took */
 			unsigned long bit = 1UL << i;
 
@@ -1354,7 +1354,7 @@
 static void drop_parsed_module_refcounts(unsigned long subsys_mask)
 {
 	int i;
-	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
+	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 		unsigned long bit = 1UL << i;
 
 		if (!(bit & subsys_mask))
@@ -4442,8 +4442,7 @@
 	 * since cgroup_init_subsys will have already taken care of it.
 	 */
 	if (ss->module == NULL) {
-		/* a few sanity checks */
-		BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
+		/* a sanity check */
 		BUG_ON(subsys[ss->subsys_id] != ss);
 		return 0;
 	}
@@ -4457,7 +4456,7 @@
 	 */
 	mutex_lock(&cgroup_mutex);
 	/* find the first empty slot in the array */
-	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
+	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
 		if (subsys[i] == NULL)
 			break;
 	}
@@ -4560,7 +4559,6 @@
 
 	mutex_lock(&cgroup_mutex);
 	/* deassign the subsys_id */
-	BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
 	subsys[ss->subsys_id] = NULL;
 
 	/* remove subsystem from rootnode's list of subsystems */
@@ -4623,10 +4621,13 @@
 	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->module)
+			continue;
+
 		BUG_ON(!ss->name);
 		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
 		BUG_ON(!ss->create);
@@ -4659,9 +4660,12 @@
 	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->module)
+			continue;
 		if (!ss->early_init)
 			cgroup_init_subsys(ss);
 		if (ss->use_id)
@@ -4856,13 +4860,16 @@
 {
 	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->module)
+				continue;
+
 			if (ss->fork)
 				ss->fork(child);
 		}
@@ -4967,12 +4974,13 @@
 	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->module)
+				continue;
+
 			if (ss->exit) {
 				struct cgroup *old_cgrp =
 					rcu_dereference_raw(cg->subsys[i])->cgroup;
@@ -5158,13 +5166,17 @@
 	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->module)
+				continue;
+
 			if (!strcmp(token, ss->name)) {
 				ss->disabled = 1;
 				printk(KERN_INFO "Disabling %s control group"