Merge tag 'cgroup-for-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cgroup rstat shared the tracking tree across all controllers with the
   rationale being that a cgroup which is using one resource is likely
   to be using other resources at the same time (ie. if something is
   allocating memory, it's probably consuming CPU cycles).

   However, this turned out to not scale very well especially with memcg
   using rstat for internal operations which made memcg stat read and
   flush patterns substantially different from other controllers. JP
   Kobryn split the rstat tree per controller.

 - cgroup BPF support was hooking into cgroup init/exit paths directly.

   Convert them to use a notifier chain instead so that other usages can
   be added easily. The two of the patches which implement this are
   mislabeled as belonging to sched_ext instead of cgroup. Sorry.

 - Relatively minor cpuset updates

 - Documentation updates

* tag 'cgroup-for-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (23 commits)
  sched_ext: Convert cgroup BPF support to use cgroup_lifetime_notifier
  sched_ext: Introduce cgroup_lifetime_notifier
  cgroup: Minor reorganization of cgroup_create()
  cgroup, docs: cpu controller's interaction with various scheduling policies
  cgroup, docs: convert space indentation to tab indentation
  cgroup: avoid per-cpu allocation of size zero rstat cpu locks
  cgroup, docs: be specific about bandwidth control of rt processes
  cgroup: document the rstat per-cpu initialization
  cgroup: helper for checking rstat participation of css
  cgroup: use subsystem-specific rstat locks to avoid contention
  cgroup: use separate rstat trees for each subsystem
  cgroup: compare css to cgroup::self in helper for distingushing css
  cgroup: warn on rstat usage by early init subsystems
  cgroup/cpuset: drop useless cpumask_empty() in compute_effective_exclusive_cpumask()
  cgroup/rstat: Improve cgroup_rstat_push_children() documentation
  cgroup: fix goto ordering in cgroup_init()
  cgroup: fix pointer check in css_rstat_init()
  cgroup/cpuset: Add warnings to catch inconsistency in exclusive CPUs
  cgroup/cpuset: Fix obsolete comment in cpuset_css_offline()
  cgroup/cpuset: Always use cpu_active_mask
  ...

1 files changed, 301 insertions, 159 deletions

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index b2239156b7de..ce4752ab9e09 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -9,18 +9,52 @@
 
 #include <trace/events/cgroup.h>
 
-static DEFINE_SPINLOCK(cgroup_rstat_lock);
-static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
+static DEFINE_SPINLOCK(rstat_base_lock);
+static DEFINE_PER_CPU(raw_spinlock_t, rstat_base_cpu_lock);
 
 static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu);
 
-static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu)
+/*
+ * Determines whether a given css can participate in rstat.
+ * css's that are cgroup::self use rstat for base stats.
+ * Other css's associated with a subsystem use rstat only when
+ * they define the ss->css_rstat_flush callback.
+ */
+static inline bool css_uses_rstat(struct cgroup_subsys_state *css)
+{
+	return css_is_self(css) || css->ss->css_rstat_flush != NULL;
+}
+
+static struct css_rstat_cpu *css_rstat_cpu(
+		struct cgroup_subsys_state *css, int cpu)
+{
+	return per_cpu_ptr(css->rstat_cpu, cpu);
+}
+
+static struct cgroup_rstat_base_cpu *cgroup_rstat_base_cpu(
+		struct cgroup *cgrp, int cpu)
 {
-	return per_cpu_ptr(cgrp->rstat_cpu, cpu);
+	return per_cpu_ptr(cgrp->rstat_base_cpu, cpu);
+}
+
+static spinlock_t *ss_rstat_lock(struct cgroup_subsys *ss)
+{
+	if (ss)
+		return &ss->rstat_ss_lock;
+
+	return &rstat_base_lock;
+}
+
+static raw_spinlock_t *ss_rstat_cpu_lock(struct cgroup_subsys *ss, int cpu)
+{
+	if (ss)
+		return per_cpu_ptr(ss->rstat_ss_cpu_lock, cpu);
+
+	return per_cpu_ptr(&rstat_base_cpu_lock, cpu);
 }
 
 /*
- * Helper functions for rstat per CPU lock (cgroup_rstat_cpu_lock).
+ * Helper functions for rstat per CPU locks.
  *
  * This makes it easier to diagnose locking issues and contention in
  * production environments. The parameter @fast_path determine the
@@ -28,20 +62,23 @@ static struct cgroup_rstat_cpu *cgroup_rstat_cpu(struct cgroup *cgrp, int cpu)
  * operations without handling high-frequency fast-path "update" events.
  */
 static __always_inline
-unsigned long _cgroup_rstat_cpu_lock(raw_spinlock_t *cpu_lock, int cpu,
-				     struct cgroup *cgrp, const bool fast_path)
+unsigned long _css_rstat_cpu_lock(struct cgroup_subsys_state *css, int cpu,
+		const bool fast_path)
 {
+	struct cgroup *cgrp = css->cgroup;
+	raw_spinlock_t *cpu_lock;
 	unsigned long flags;
 	bool contended;
 
 	/*
-	 * The _irqsave() is needed because cgroup_rstat_lock is
-	 * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
-	 * this lock with the _irq() suffix only disables interrupts on
-	 * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
-	 * interrupts on both configurations. The _irqsave() ensures
-	 * that interrupts are always disabled and later restored.
+	 * The _irqsave() is needed because the locks used for flushing are
+	 * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring this lock
+	 * with the _irq() suffix only disables interrupts on a non-PREEMPT_RT
+	 * kernel. The raw_spinlock_t below disables interrupts on both
+	 * configurations. The _irqsave() ensures that interrupts are always
+	 * disabled and later restored.
 	 */
+	cpu_lock = ss_rstat_cpu_lock(css->ss, cpu);
 	contended = !raw_spin_trylock_irqsave(cpu_lock, flags);
 	if (contended) {
 		if (fast_path)
@@ -61,50 +98,59 @@ unsigned long _cgroup_rstat_cpu_lock(raw_spinlock_t *cpu_lock, int cpu,
 }
 
 static __always_inline
-void _cgroup_rstat_cpu_unlock(raw_spinlock_t *cpu_lock, int cpu,
-			      struct cgroup *cgrp, unsigned long flags,
-			      const bool fast_path)
+void _css_rstat_cpu_unlock(struct cgroup_subsys_state *css, int cpu,
+		unsigned long flags, const bool fast_path)
 {
+	struct cgroup *cgrp = css->cgroup;
+	raw_spinlock_t *cpu_lock;
+
 	if (fast_path)
 		trace_cgroup_rstat_cpu_unlock_fastpath(cgrp, cpu, false);
 	else
 		trace_cgroup_rstat_cpu_unlock(cgrp, cpu, false);
 
+	cpu_lock = ss_rstat_cpu_lock(css->ss, cpu);
 	raw_spin_unlock_irqrestore(cpu_lock, flags);
 }
 
 /**
- * cgroup_rstat_updated - keep track of updated rstat_cpu
- * @cgrp: target cgroup
+ * css_rstat_updated - keep track of updated rstat_cpu
+ * @css: target cgroup subsystem state
  * @cpu: cpu on which rstat_cpu was updated
  *
- * @cgrp's rstat_cpu on @cpu was updated.  Put it on the parent's matching
- * rstat_cpu->updated_children list.  See the comment on top of
- * cgroup_rstat_cpu definition for details.
+ * @css's rstat_cpu on @cpu was updated. Put it on the parent's matching
+ * rstat_cpu->updated_children list. See the comment on top of
+ * css_rstat_cpu definition for details.
  */
-__bpf_kfunc void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
+__bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu)
 {
-	raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
 	unsigned long flags;
 
 	/*
+	 * Since bpf programs can call this function, prevent access to
+	 * uninitialized rstat pointers.
+	 */
+	if (!css_uses_rstat(css))
+		return;
+
+	/*
 	 * Speculative already-on-list test. This may race leading to
 	 * temporary inaccuracies, which is fine.
 	 *
 	 * Because @parent's updated_children is terminated with @parent
-	 * instead of NULL, we can tell whether @cgrp is on the list by
+	 * instead of NULL, we can tell whether @css is on the list by
 	 * testing the next pointer for NULL.
 	 */
-	if (data_race(cgroup_rstat_cpu(cgrp, cpu)->updated_next))
+	if (data_race(css_rstat_cpu(css, cpu)->updated_next))
 		return;
 
-	flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, cgrp, true);
+	flags = _css_rstat_cpu_lock(css, cpu, true);
 
-	/* put @cgrp and all ancestors on the corresponding updated lists */
+	/* put @css and all ancestors on the corresponding updated lists */
 	while (true) {
-		struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
-		struct cgroup *parent = cgroup_parent(cgrp);
-		struct cgroup_rstat_cpu *prstatc;
+		struct css_rstat_cpu *rstatc = css_rstat_cpu(css, cpu);
+		struct cgroup_subsys_state *parent = css->parent;
+		struct css_rstat_cpu *prstatc;
 
 		/*
 		 * Both additions and removals are bottom-up.  If a cgroup
@@ -115,53 +161,78 @@ __bpf_kfunc void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
 
 		/* Root has no parent to link it to, but mark it busy */
 		if (!parent) {
-			rstatc->updated_next = cgrp;
+			rstatc->updated_next = css;
 			break;
 		}
 
-		prstatc = cgroup_rstat_cpu(parent, cpu);
+		prstatc = css_rstat_cpu(parent, cpu);
 		rstatc->updated_next = prstatc->updated_children;
-		prstatc->updated_children = cgrp;
+		prstatc->updated_children = css;
 
-		cgrp = parent;
+		css = parent;
 	}
 
-	_cgroup_rstat_cpu_unlock(cpu_lock, cpu, cgrp, flags, true);
+	_css_rstat_cpu_unlock(css, cpu, flags, true);
 }
 
 /**
- * cgroup_rstat_push_children - push children cgroups into the given list
+ * css_rstat_push_children - push children css's into the given list
  * @head: current head of the list (= subtree root)
  * @child: first child of the root
  * @cpu: target cpu
- * Return: A new singly linked list of cgroups to be flush
+ * Return: A new singly linked list of css's to be flushed
  *
- * Iteratively traverse down the cgroup_rstat_cpu updated tree level by
+ * Iteratively traverse down the css_rstat_cpu updated tree level by
  * level and push all the parents first before their next level children
- * into a singly linked list built from the tail backward like "pushing"
- * cgroups into a stack. The root is pushed by the caller.
+ * into a singly linked list via the rstat_flush_next pointer built from the
+ * tail backward like "pushing" css's into a stack. The root is pushed by
+ * the caller.
  */
-static struct cgroup *cgroup_rstat_push_children(struct cgroup *head,
-						 struct cgroup *child, int cpu)
+static struct cgroup_subsys_state *css_rstat_push_children(
+		struct cgroup_subsys_state *head,
+		struct cgroup_subsys_state *child, int cpu)
 {
-	struct cgroup *chead = child;	/* Head of child cgroup level */
-	struct cgroup *ghead = NULL;	/* Head of grandchild cgroup level */
-	struct cgroup *parent, *grandchild;
-	struct cgroup_rstat_cpu *crstatc;
+	struct cgroup_subsys_state *cnext = child;	/* Next head of child css level */
+	struct cgroup_subsys_state *ghead = NULL;	/* Head of grandchild css level */
+	struct cgroup_subsys_state *parent, *grandchild;
+	struct css_rstat_cpu *crstatc;
 
 	child->rstat_flush_next = NULL;
 
+	/*
+	 * The subsystem rstat lock must be held for the whole duration from
+	 * here as the rstat_flush_next list is being constructed to when
+	 * it is consumed later in css_rstat_flush().
+	 */
+	lockdep_assert_held(ss_rstat_lock(head->ss));
+
+	/*
+	 * Notation: -> updated_next pointer
+	 *	     => rstat_flush_next pointer
+	 *
+	 * Assuming the following sample updated_children lists:
+	 *  P: C1 -> C2 -> P
+	 *  C1: G11 -> G12 -> C1
+	 *  C2: G21 -> G22 -> C2
+	 *
+	 * After 1st iteration:
+	 *  head => C2 => C1 => NULL
+	 *  ghead => G21 => G11 => NULL
+	 *
+	 * After 2nd iteration:
+	 *  head => G12 => G11 => G22 => G21 => C2 => C1 => NULL
+	 */
 next_level:
-	while (chead) {
-		child = chead;
-		chead = child->rstat_flush_next;
-		parent = cgroup_parent(child);
+	while (cnext) {
+		child = cnext;
+		cnext = child->rstat_flush_next;
+		parent = child->parent;
 
-		/* updated_next is parent cgroup terminated */
+		/* updated_next is parent cgroup terminated if !NULL */
 		while (child != parent) {
 			child->rstat_flush_next = head;
 			head = child;
-			crstatc = cgroup_rstat_cpu(child, cpu);
+			crstatc = css_rstat_cpu(child, cpu);
 			grandchild = crstatc->updated_children;
 			if (grandchild != child) {
 				/* Push the grand child to the next level */
@@ -175,7 +246,7 @@ next_level:
 	}
 
 	if (ghead) {
-		chead = ghead;
+		cnext = ghead;
 		ghead = NULL;
 		goto next_level;
 	}
@@ -183,31 +254,31 @@ next_level:
 }
 
 /**
- * cgroup_rstat_updated_list - return a list of updated cgroups to be flushed
- * @root: root of the cgroup subtree to traverse
+ * css_rstat_updated_list - build a list of updated css's to be flushed
+ * @root: root of the css subtree to traverse
  * @cpu: target cpu
- * Return: A singly linked list of cgroups to be flushed
+ * Return: A singly linked list of css's to be flushed
  *
  * Walks the updated rstat_cpu tree on @cpu from @root.  During traversal,
- * each returned cgroup is unlinked from the updated tree.
+ * each returned css is unlinked from the updated tree.
  *
  * The only ordering guarantee is that, for a parent and a child pair
  * covered by a given traversal, the child is before its parent in
  * the list.
  *
  * Note that updated_children is self terminated and points to a list of
- * child cgroups if not empty. Whereas updated_next is like a sibling link
- * within the children list and terminated by the parent cgroup. An exception
- * here is the cgroup root whose updated_next can be self terminated.
+ * child css's if not empty. Whereas updated_next is like a sibling link
+ * within the children list and terminated by the parent css. An exception
+ * here is the css root whose updated_next can be self terminated.
  */
-static struct cgroup *cgroup_rstat_updated_list(struct cgroup *root, int cpu)
+static struct cgroup_subsys_state *css_rstat_updated_list(
+		struct cgroup_subsys_state *root, int cpu)
 {
-	raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
-	struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(root, cpu);
-	struct cgroup *head = NULL, *parent, *child;
+	struct css_rstat_cpu *rstatc = css_rstat_cpu(root, cpu);
+	struct cgroup_subsys_state *head = NULL, *parent, *child;
 	unsigned long flags;
 
-	flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, root, false);
+	flags = _css_rstat_cpu_lock(root, cpu, false);
 
 	/* Return NULL if this subtree is not on-list */
 	if (!rstatc->updated_next)
@@ -217,17 +288,17 @@ static struct cgroup *cgroup_rstat_updated_list(struct cgroup *root, int cpu)
 	 * Unlink @root from its parent. As the updated_children list is
 	 * singly linked, we have to walk it to find the removal point.
 	 */
-	parent = cgroup_parent(root);
+	parent = root->parent;
 	if (parent) {
-		struct cgroup_rstat_cpu *prstatc;
-		struct cgroup **nextp;
+		struct css_rstat_cpu *prstatc;
+		struct cgroup_subsys_state **nextp;
 
-		prstatc = cgroup_rstat_cpu(parent, cpu);
+		prstatc = css_rstat_cpu(parent, cpu);
 		nextp = &prstatc->updated_children;
 		while (*nextp != root) {
-			struct cgroup_rstat_cpu *nrstatc;
+			struct css_rstat_cpu *nrstatc;
 
-			nrstatc = cgroup_rstat_cpu(*nextp, cpu);
+			nrstatc = css_rstat_cpu(*nextp, cpu);
 			WARN_ON_ONCE(*nextp == parent);
 			nextp = &nrstatc->updated_next;
 		}
@@ -242,16 +313,16 @@ static struct cgroup *cgroup_rstat_updated_list(struct cgroup *root, int cpu)
 	child = rstatc->updated_children;
 	rstatc->updated_children = root;
 	if (child != root)
-		head = cgroup_rstat_push_children(head, child, cpu);
+		head = css_rstat_push_children(head, child, cpu);
 unlock_ret:
-	_cgroup_rstat_cpu_unlock(cpu_lock, cpu, root, flags, false);
+	_css_rstat_cpu_unlock(root, cpu, flags, false);
 	return head;
 }
 
 /*
  * A hook for bpf stat collectors to attach to and flush their stats.
- * Together with providing bpf kfuncs for cgroup_rstat_updated() and
- * cgroup_rstat_flush(), this enables a complete workflow where bpf progs that
+ * Together with providing bpf kfuncs for css_rstat_updated() and
+ * css_rstat_flush(), this enables a complete workflow where bpf progs that
  * collect cgroup stats can integrate with rstat for efficient flushing.
  *
  * A static noinline declaration here could cause the compiler to optimize away
@@ -271,7 +342,7 @@ __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
 __bpf_hook_end();
 
 /*
- * Helper functions for locking cgroup_rstat_lock.
+ * Helper functions for locking.
  *
  * This makes it easier to diagnose locking issues and contention in
  * production environments.  The parameter @cpu_in_loop indicate lock
@@ -279,115 +350,186 @@ __bpf_hook_end();
  * value -1 is used when obtaining the main lock else this is the CPU
  * number processed last.
  */
-static inline void __cgroup_rstat_lock(struct cgroup *cgrp, int cpu_in_loop)
-	__acquires(&cgroup_rstat_lock)
+static inline void __css_rstat_lock(struct cgroup_subsys_state *css,
+		int cpu_in_loop)
+	__acquires(ss_rstat_lock(css->ss))
 {
+	struct cgroup *cgrp = css->cgroup;
+	spinlock_t *lock;
 	bool contended;
 
-	contended = !spin_trylock_irq(&cgroup_rstat_lock);
+	lock = ss_rstat_lock(css->ss);
+	contended = !spin_trylock_irq(lock);
 	if (contended) {
 		trace_cgroup_rstat_lock_contended(cgrp, cpu_in_loop, contended);
-		spin_lock_irq(&cgroup_rstat_lock);
+		spin_lock_irq(lock);
 	}
 	trace_cgroup_rstat_locked(cgrp, cpu_in_loop, contended);
 }
 
-static inline void __cgroup_rstat_unlock(struct cgroup *cgrp, int cpu_in_loop)
-	__releases(&cgroup_rstat_lock)
+static inline void __css_rstat_unlock(struct cgroup_subsys_state *css,
+				      int cpu_in_loop)
+	__releases(ss_rstat_lock(css->ss))
 {
+	struct cgroup *cgrp = css->cgroup;
+	spinlock_t *lock;
+
+	lock = ss_rstat_lock(css->ss);
 	trace_cgroup_rstat_unlock(cgrp, cpu_in_loop, false);
-	spin_unlock_irq(&cgroup_rstat_lock);
+	spin_unlock_irq(lock);
 }
 
 /**
- * cgroup_rstat_flush - flush stats in @cgrp's subtree
- * @cgrp: target cgroup
+ * css_rstat_flush - flush stats in @css's rstat subtree
+ * @css: target cgroup subsystem state
  *
- * Collect all per-cpu stats in @cgrp's subtree into the global counters
- * and propagate them upwards.  After this function returns, all cgroups in
- * the subtree have up-to-date ->stat.
+ * Collect all per-cpu stats in @css's subtree into the global counters
+ * and propagate them upwards. After this function returns, all rstat
+ * nodes in the subtree have up-to-date ->stat.
  *
- * This also gets all cgroups in the subtree including @cgrp off the
+ * This also gets all rstat nodes in the subtree including @css off the
  * ->updated_children lists.
  *
  * This function may block.
  */
-__bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
+__bpf_kfunc void css_rstat_flush(struct cgroup_subsys_state *css)
 {
 	int cpu;
+	bool is_self = css_is_self(css);
+
+	/*
+	 * Since bpf programs can call this function, prevent access to
+	 * uninitialized rstat pointers.
+	 */
+	if (!css_uses_rstat(css))
+		return;
 
 	might_sleep();
 	for_each_possible_cpu(cpu) {
-		struct cgroup *pos;
+		struct cgroup_subsys_state *pos;
 
 		/* Reacquire for each CPU to avoid disabling IRQs too long */
-		__cgroup_rstat_lock(cgrp, cpu);
-		pos = cgroup_rstat_updated_list(cgrp, cpu);
+		__css_rstat_lock(css, cpu);
+		pos = css_rstat_updated_list(css, cpu);
 		for (; pos; pos = pos->rstat_flush_next) {
-			struct cgroup_subsys_state *css;
-
-			cgroup_base_stat_flush(pos, cpu);
-			bpf_rstat_flush(pos, cgroup_parent(pos), cpu);
-
-			rcu_read_lock();
-			list_for_each_entry_rcu(css, &pos->rstat_css_list,
-						rstat_css_node)
-				css->ss->css_rstat_flush(css, cpu);
-			rcu_read_unlock();
+			if (is_self) {
+				cgroup_base_stat_flush(pos->cgroup, cpu);
+				bpf_rstat_flush(pos->cgroup,
+						cgroup_parent(pos->cgroup), cpu);
+			} else
+				pos->ss->css_rstat_flush(pos, cpu);
 		}
-		__cgroup_rstat_unlock(cgrp, cpu);
+		__css_rstat_unlock(css, cpu);
 		if (!cond_resched())
 			cpu_relax();
 	}
 }
 
-int cgroup_rstat_init(struct cgroup *cgrp)
+int css_rstat_init(struct cgroup_subsys_state *css)
 {
+	struct cgroup *cgrp = css->cgroup;
 	int cpu;
+	bool is_self = css_is_self(css);
+
+	if (is_self) {
+		/* the root cgrp has rstat_base_cpu preallocated */
+		if (!cgrp->rstat_base_cpu) {
+			cgrp->rstat_base_cpu = alloc_percpu(struct cgroup_rstat_base_cpu);
+			if (!cgrp->rstat_base_cpu)
+				return -ENOMEM;
+		}
+	} else if (css->ss->css_rstat_flush == NULL)
+		return 0;
+
+	/* the root cgrp's self css has rstat_cpu preallocated */
+	if (!css->rstat_cpu) {
+		css->rstat_cpu = alloc_percpu(struct css_rstat_cpu);
+		if (!css->rstat_cpu) {
+			if (is_self)
+				free_percpu(cgrp->rstat_base_cpu);
 
-	/* the root cgrp has rstat_cpu preallocated */
-	if (!cgrp->rstat_cpu) {
-		cgrp->rstat_cpu = alloc_percpu(struct cgroup_rstat_cpu);
-		if (!cgrp->rstat_cpu)
 			return -ENOMEM;
+		}
 	}
 
 	/* ->updated_children list is self terminated */
 	for_each_possible_cpu(cpu) {
-		struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
+		struct css_rstat_cpu *rstatc = css_rstat_cpu(css, cpu);
+
+		rstatc->updated_children = css;
+
+		if (is_self) {
+			struct cgroup_rstat_base_cpu *rstatbc;
 
-		rstatc->updated_children = cgrp;
-		u64_stats_init(&rstatc->bsync);
+			rstatbc = cgroup_rstat_base_cpu(cgrp, cpu);
+			u64_stats_init(&rstatbc->bsync);
+		}
 	}
 
 	return 0;
 }
 
-void cgroup_rstat_exit(struct cgroup *cgrp)
+void css_rstat_exit(struct cgroup_subsys_state *css)
 {
 	int cpu;
 
-	cgroup_rstat_flush(cgrp);
+	if (!css_uses_rstat(css))
+		return;
+
+	css_rstat_flush(css);
 
 	/* sanity check */
 	for_each_possible_cpu(cpu) {
-		struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
+		struct css_rstat_cpu *rstatc = css_rstat_cpu(css, cpu);
 
-		if (WARN_ON_ONCE(rstatc->updated_children != cgrp) ||
+		if (WARN_ON_ONCE(rstatc->updated_children != css) ||
 		    WARN_ON_ONCE(rstatc->updated_next))
 			return;
 	}
 
-	free_percpu(cgrp->rstat_cpu);
-	cgrp->rstat_cpu = NULL;
+	if (css_is_self(css)) {
+		struct cgroup *cgrp = css->cgroup;
+
+		free_percpu(cgrp->rstat_base_cpu);
+		cgrp->rstat_base_cpu = NULL;
+	}
+
+	free_percpu(css->rstat_cpu);
+	css->rstat_cpu = NULL;
 }
 
-void __init cgroup_rstat_boot(void)
+/**
+ * ss_rstat_init - subsystem-specific rstat initialization
+ * @ss: target subsystem
+ *
+ * If @ss is NULL, the static locks associated with the base stats
+ * are initialized. If @ss is non-NULL, the subsystem-specific locks
+ * are initialized.
+ */
+int __init ss_rstat_init(struct cgroup_subsys *ss)
 {
 	int cpu;
 
+#ifdef CONFIG_SMP
+	/*
+	 * On uniprocessor machines, arch_spinlock_t is defined as an empty
+	 * struct. Avoid allocating a size of zero by having this block
+	 * excluded in this case. It's acceptable to leave the subsystem locks
+	 * unitialized since the associated lock functions are no-ops in the
+	 * non-smp case.
+	 */
+	if (ss) {
+		ss->rstat_ss_cpu_lock = alloc_percpu(raw_spinlock_t);
+		if (!ss->rstat_ss_cpu_lock)
+			return -ENOMEM;
+	}
+#endif
+
+	spin_lock_init(ss_rstat_lock(ss));
 	for_each_possible_cpu(cpu)
-		raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
+		raw_spin_lock_init(ss_rstat_cpu_lock(ss, cpu));
+
+	return 0;
 }
 
 /*
@@ -420,9 +562,9 @@ static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
 
 static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 {
-	struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
+	struct cgroup_rstat_base_cpu *rstatbc = cgroup_rstat_base_cpu(cgrp, cpu);
 	struct cgroup *parent = cgroup_parent(cgrp);
-	struct cgroup_rstat_cpu *prstatc;
+	struct cgroup_rstat_base_cpu *prstatbc;
 	struct cgroup_base_stat delta;
 	unsigned seq;
 
@@ -432,15 +574,15 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 
 	/* fetch the current per-cpu values */
 	do {
-		seq = __u64_stats_fetch_begin(&rstatc->bsync);
-		delta = rstatc->bstat;
-	} while (__u64_stats_fetch_retry(&rstatc->bsync, seq));
+		seq = __u64_stats_fetch_begin(&rstatbc->bsync);
+		delta = rstatbc->bstat;
+	} while (__u64_stats_fetch_retry(&rstatbc->bsync, seq));
 
 	/* propagate per-cpu delta to cgroup and per-cpu global statistics */
-	cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
+	cgroup_base_stat_sub(&delta, &rstatbc->last_bstat);
 	cgroup_base_stat_add(&cgrp->bstat, &delta);
-	cgroup_base_stat_add(&rstatc->last_bstat, &delta);
-	cgroup_base_stat_add(&rstatc->subtree_bstat, &delta);
+	cgroup_base_stat_add(&rstatbc->last_bstat, &delta);
+	cgroup_base_stat_add(&rstatbc->subtree_bstat, &delta);
 
 	/* propagate cgroup and per-cpu global delta to parent (unless that's root) */
 	if (cgroup_parent(parent)) {
@@ -449,73 +591,73 @@ static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
 		cgroup_base_stat_add(&parent->bstat, &delta);
 		cgroup_base_stat_add(&cgrp->last_bstat, &delta);
 
-		delta = rstatc->subtree_bstat;
-		prstatc = cgroup_rstat_cpu(parent, cpu);
-		cgroup_base_stat_sub(&delta, &rstatc->last_subtree_bstat);
-		cgroup_base_stat_add(&prstatc->subtree_bstat, &delta);
-		cgroup_base_stat_add(&rstatc->last_subtree_bstat, &delta);
+		delta = rstatbc->subtree_bstat;
+		prstatbc = cgroup_rstat_base_cpu(parent, cpu);
+		cgroup_base_stat_sub(&delta, &rstatbc->last_subtree_bstat);
+		cgroup_base_stat_add(&prstatbc->subtree_bstat, &delta);
+		cgroup_base_stat_add(&rstatbc->last_subtree_bstat, &delta);
 	}
 }
 
-static struct cgroup_rstat_cpu *
+static struct cgroup_rstat_base_cpu *
 cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
 {
-	struct cgroup_rstat_cpu *rstatc;
+	struct cgroup_rstat_base_cpu *rstatbc;
 
-	rstatc = get_cpu_ptr(cgrp->rstat_cpu);
-	*flags = u64_stats_update_begin_irqsave(&rstatc->bsync);
-	return rstatc;
+	rstatbc = get_cpu_ptr(cgrp->rstat_base_cpu);
+	*flags = u64_stats_update_begin_irqsave(&rstatbc->bsync);
+	return rstatbc;
 }
 
 static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
-						 struct cgroup_rstat_cpu *rstatc,
+						 struct cgroup_rstat_base_cpu *rstatbc,
 						 unsigned long flags)
 {
-	u64_stats_update_end_irqrestore(&rstatc->bsync, flags);
-	cgroup_rstat_updated(cgrp, smp_processor_id());
-	put_cpu_ptr(rstatc);
+	u64_stats_update_end_irqrestore(&rstatbc->bsync, flags);
+	css_rstat_updated(&cgrp->self, smp_processor_id());
+	put_cpu_ptr(rstatbc);
 }
 
 void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
 {
-	struct cgroup_rstat_cpu *rstatc;
+	struct cgroup_rstat_base_cpu *rstatbc;
 	unsigned long flags;
 
-	rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
-	rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
-	cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
+	rstatbc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
+	rstatbc->bstat.cputime.sum_exec_runtime += delta_exec;
+	cgroup_base_stat_cputime_account_end(cgrp, rstatbc, flags);
 }
 
 void __cgroup_account_cputime_field(struct cgroup *cgrp,
 				    enum cpu_usage_stat index, u64 delta_exec)
 {
-	struct cgroup_rstat_cpu *rstatc;
+	struct cgroup_rstat_base_cpu *rstatbc;
 	unsigned long flags;
 
-	rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
+	rstatbc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);
 
 	switch (index) {
 	case CPUTIME_NICE:
-		rstatc->bstat.ntime += delta_exec;
+		rstatbc->bstat.ntime += delta_exec;
 		fallthrough;
 	case CPUTIME_USER:
-		rstatc->bstat.cputime.utime += delta_exec;
+		rstatbc->bstat.cputime.utime += delta_exec;
 		break;
 	case CPUTIME_SYSTEM:
 	case CPUTIME_IRQ:
 	case CPUTIME_SOFTIRQ:
-		rstatc->bstat.cputime.stime += delta_exec;
+		rstatbc->bstat.cputime.stime += delta_exec;
 		break;
 #ifdef CONFIG_SCHED_CORE
 	case CPUTIME_FORCEIDLE:
-		rstatc->bstat.forceidle_sum += delta_exec;
+		rstatbc->bstat.forceidle_sum += delta_exec;
 		break;
 #endif
 	default:
 		break;
 	}
 
-	cgroup_base_stat_cputime_account_end(cgrp, rstatc, flags);
+	cgroup_base_stat_cputime_account_end(cgrp, rstatbc, flags);
 }
 
 /*
@@ -574,12 +716,12 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
 	struct cgroup_base_stat bstat;
 
 	if (cgroup_parent(cgrp)) {
-		cgroup_rstat_flush(cgrp);
-		__cgroup_rstat_lock(cgrp, -1);
+		css_rstat_flush(&cgrp->self);
+		__css_rstat_lock(&cgrp->self, -1);
 		bstat = cgrp->bstat;
 		cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
 			       &bstat.cputime.utime, &bstat.cputime.stime);
-		__cgroup_rstat_unlock(cgrp, -1);
+		__css_rstat_unlock(&cgrp->self, -1);
 	} else {
 		root_cgroup_cputime(&bstat);
 	}
@@ -601,10 +743,10 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
 	cgroup_force_idle_show(seq, &bstat);
 }
 
-/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
+/* Add bpf kfuncs for css_rstat_updated() and css_rstat_flush() */
 BTF_KFUNCS_START(bpf_rstat_kfunc_ids)
-BTF_ID_FLAGS(func, cgroup_rstat_updated)
-BTF_ID_FLAGS(func, cgroup_rstat_flush, KF_SLEEPABLE)
+BTF_ID_FLAGS(func, css_rstat_updated)
+BTF_ID_FLAGS(func, css_rstat_flush, KF_SLEEPABLE)
 BTF_KFUNCS_END(bpf_rstat_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {