// SPDX-License-Identifier: GPL-2.0-only
#include "cgroup-internal.h"

#include <linux/sched/cputime.h>

#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>

#include <trace/events/cgroup.h>

static DEFINE_SPINLOCK(rstat_base_lock);
static DEFINE_PER_CPU(struct llist_head, rstat_backlog_list);

static void cgroup_base_stat_flush(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_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 inline struct llist_head *ss_lhead_cpu(struct cgroup_subsys *ss, int cpu)
{
        if (ss)
                return per_cpu_ptr(ss->lhead, cpu);
        return per_cpu_ptr(&rstat_backlog_list, cpu);
}

/**
 * css_rstat_updated - keep track of updated rstat_cpu
 * @css: target cgroup subsystem state
 * @cpu: cpu on which rstat_cpu was updated
 *
 * Atomically inserts the css in the ss's llist for the given cpu. This is
 * reentrant safe i.e. safe against softirq, hardirq and nmi. The ss's llist
 * will be processed at the flush time to create the update tree.
 *
 * NOTE: if the user needs the guarantee that the updater either add itself in
 * the lockless list or the concurrent flusher flushes its updated stats, a
 * memory barrier is needed before the call to css_rstat_updated() i.e. a
 * barrier after updating the per-cpu stats and before calling
 * css_rstat_updated().
 */
__bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu)
{
        struct llist_head *lhead;
        struct css_rstat_cpu *rstatc;
        struct llist_node *self;

        /*
         * Since bpf programs can call this function, prevent access to
         * uninitialized rstat pointers.
         */
        if (!css_uses_rstat(css))
                return;

        lockdep_assert_preemption_disabled();

        /*
         * For archs withnot nmi safe cmpxchg or percpu ops support, ignore
         * the requests from nmi context.
         */
        if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) ||
             !IS_ENABLED(CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS)) && in_nmi())
                return;

        rstatc = css_rstat_cpu(css, cpu);
        /*
         * If already on list return. This check is racy and smp_mb() is needed
         * to pair it with the smp_mb() in css_process_update_tree() if the
         * guarantee that the updated stats are visible to concurrent flusher is
         * needed.
         */
        if (llist_on_list(&rstatc->lnode))
                return;

        /*
         * This function can be renentered by irqs and nmis for the same cgroup
         * and may try to insert the same per-cpu lnode into the llist. Note
         * that llist_add() does not protect against such scenarios. In addition
         * this same per-cpu lnode can be modified through init_llist_node()
         * from css_rstat_flush() running on a different CPU.
         *
         * To protect against such stacked contexts of irqs/nmis, we use the
         * fact that lnode points to itself when not on a list and then use
         * try_cmpxchg() to atomically set to NULL to select the winner
         * which will call llist_add(). The losers can assume the insertion is
         * successful and the winner will eventually add the per-cpu lnode to
         * the llist.
         *
         * Please note that we can not use this_cpu_cmpxchg() here as on some
         * archs it is not safe against modifications from multiple CPUs.
         */
        self = &rstatc->lnode;
        if (!try_cmpxchg(&rstatc->lnode.next, &self, NULL))
                return;

        lhead = ss_lhead_cpu(css->ss, cpu);
        llist_add(&rstatc->lnode, lhead);
}

static void __css_process_update_tree(struct cgroup_subsys_state *css, int cpu)
{
        /* put @css and all ancestors on the corresponding updated lists */
        while (true) {
                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
                 * is already in the tree, all ancestors are.
                 */
                if (rstatc->updated_next)
                        break;

                /* Root has no parent to link it to, but mark it busy */
                if (!parent) {
                        rstatc->updated_next = css;
                        break;
                }

                prstatc = css_rstat_cpu(parent, cpu);
                rstatc->updated_next = prstatc->updated_children;
                prstatc->updated_children = css;

                css = parent;
        }
}

static void css_process_update_tree(struct cgroup_subsys *ss, int cpu)
{
        struct llist_head *lhead = ss_lhead_cpu(ss, cpu);
        struct llist_node *lnode;

        while ((lnode = llist_del_first_init(lhead))) {
                struct css_rstat_cpu *rstatc;

                /*
                 * smp_mb() is needed here (more specifically in between
                 * init_llist_node() and per-cpu stats flushing) if the
                 * guarantee is required by a rstat user where etiher the
                 * updater should add itself on the lockless list or the
                 * flusher flush the stats updated by the updater who have
                 * observed that they are already on the list. The
                 * corresponding barrier pair for this one should be before
                 * css_rstat_updated() by the user.
                 *
                 * For now, there aren't any such user, so not adding the
                 * barrier here but if such a use-case arise, please add
                 * smp_mb() here.
                 */

                rstatc = container_of(lnode, struct css_rstat_cpu, lnode);
                __css_process_update_tree(rstatc->owner, cpu);
        }
}

/**
 * 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 css's to be flushed
 *
 * 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 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_subsys_state *css_rstat_push_children(
                struct cgroup_subsys_state *head,
                struct cgroup_subsys_state *child, int cpu)
{
        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 (cnext) {
                child = cnext;
                cnext = child->rstat_flush_next;
                parent = child->parent;

                /* updated_next is parent cgroup terminated if !NULL */
                while (child != parent) {
                        child->rstat_flush_next = head;
                        head = child;
                        crstatc = css_rstat_cpu(child, cpu);
                        grandchild = crstatc->updated_children;
                        if (grandchild != child) {
                                /* Push the grand child to the next level */
                                crstatc->updated_children = child;
                                grandchild->rstat_flush_next = ghead;
                                ghead = grandchild;
                        }
                        child = crstatc->updated_next;
                        crstatc->updated_next = NULL;
                }
        }

        if (ghead) {
                cnext = ghead;
                ghead = NULL;
                goto next_level;
        }
        return head;
}

/**
 * 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 css's to be flushed
 *
 * Walks the updated rstat_cpu tree on @cpu from @root.  During traversal,
 * 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 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_subsys_state *css_rstat_updated_list(
                struct cgroup_subsys_state *root, int cpu)
{
        struct css_rstat_cpu *rstatc = css_rstat_cpu(root, cpu);
        struct cgroup_subsys_state *head = NULL, *parent, *child;

        css_process_update_tree(root->ss, cpu);

        /* Return NULL if this subtree is not on-list */
        if (!rstatc->updated_next)
                return NULL;

        /*
         * Unlink @root from its parent. As the updated_children list is
         * singly linked, we have to walk it to find the removal point.
         */
        parent = root->parent;
        if (parent) {
                struct css_rstat_cpu *prstatc;
                struct cgroup_subsys_state **nextp;

                prstatc = css_rstat_cpu(parent, cpu);
                nextp = &prstatc->updated_children;
                while (*nextp != root) {
                        struct css_rstat_cpu *nrstatc;

                        nrstatc = css_rstat_cpu(*nextp, cpu);
                        WARN_ON_ONCE(*nextp == parent);
                        nextp = &nrstatc->updated_next;
                }
                *nextp = rstatc->updated_next;
        }

        rstatc->updated_next = NULL;

        /* Push @root to the list first before pushing the children */
        head = root;
        root->rstat_flush_next = NULL;
        child = rstatc->updated_children;
        rstatc->updated_children = root;
        if (child != root)
                head = css_rstat_push_children(head, child, cpu);

        return head;
}

/*
 * A hook for bpf stat collectors to attach to and flush their stats.
 * 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
 * the function. A global noinline declaration will keep the definition, but may
 * optimize away the callsite. Therefore, __weak is needed to ensure that the
 * call is still emitted, by telling the compiler that we don't know what the
 * function might eventually be.
 */

__bpf_hook_start();

__weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
                                     struct cgroup *parent, int cpu)
{
}

__bpf_hook_end();

/*
 * Helper functions for locking.
 *
 * This makes it easier to diagnose locking issues and contention in
 * production environments.  The parameter @cpu_in_loop indicate lock
 * was released and re-taken when collection data from the CPUs. The
 * value -1 is used when obtaining the main lock else this is the CPU
 * number processed last.
 */
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;

        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(lock);
        }
        trace_cgroup_rstat_locked(cgrp, cpu_in_loop, contended);
}

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(lock);
}

/**
 * css_rstat_flush - flush stats in @css's rstat subtree
 * @css: target cgroup subsystem state
 *
 * 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 rstat nodes in the subtree including @css off the
 * ->updated_children lists.
 *
 * This function may block.
 */
__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_subsys_state *pos;

                /* Reacquire for each CPU to avoid disabling IRQs too long */
                __css_rstat_lock(css, cpu);
                pos = css_rstat_updated_list(css, cpu);
                for (; pos; pos = pos->rstat_flush_next) {
                        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);
                }
                __css_rstat_unlock(css, cpu);
                if (!cond_resched())
                        cpu_relax();
        }
}

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);

                        return -ENOMEM;
                }
        }

        /* ->updated_children list is self terminated */
        for_each_possible_cpu(cpu) {
                struct css_rstat_cpu *rstatc = css_rstat_cpu(css, cpu);

                rstatc->owner = rstatc->updated_children = css;
                init_llist_node(&rstatc->lnode);

                if (is_self) {
                        struct cgroup_rstat_base_cpu *rstatbc;

                        rstatbc = cgroup_rstat_base_cpu(cgrp, cpu);
                        u64_stats_init(&rstatbc->bsync);
                }
        }

        return 0;
}

void css_rstat_exit(struct cgroup_subsys_state *css)
{
        int cpu;

        if (!css_uses_rstat(css))
                return;

        if (!css->rstat_cpu)
                return;

        css_rstat_flush(css);

        /* sanity check */
        for_each_possible_cpu(cpu) {
                struct css_rstat_cpu *rstatc = css_rstat_cpu(css, cpu);

                if (WARN_ON_ONCE(rstatc->updated_children != css) ||
                    WARN_ON_ONCE(rstatc->updated_next))
                        return;
        }

        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;
}

/**
 * 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;

        if (ss) {
                ss->lhead = alloc_percpu(struct llist_head);
                if (!ss->lhead)
                        return -ENOMEM;
        }

        spin_lock_init(ss_rstat_lock(ss));
        for_each_possible_cpu(cpu)
                init_llist_head(ss_lhead_cpu(ss, cpu));

        return 0;
}

/*
 * Functions for cgroup basic resource statistics implemented on top of
 * rstat.
 */
static void cgroup_base_stat_add(struct cgroup_base_stat *dst_bstat,
                                 struct cgroup_base_stat *src_bstat)
{
        dst_bstat->cputime.utime += src_bstat->cputime.utime;
        dst_bstat->cputime.stime += src_bstat->cputime.stime;
        dst_bstat->cputime.sum_exec_runtime += src_bstat->cputime.sum_exec_runtime;
#ifdef CONFIG_SCHED_CORE
        dst_bstat->forceidle_sum += src_bstat->forceidle_sum;
#endif
        dst_bstat->ntime += src_bstat->ntime;
}

static void cgroup_base_stat_sub(struct cgroup_base_stat *dst_bstat,
                                 struct cgroup_base_stat *src_bstat)
{
        dst_bstat->cputime.utime -= src_bstat->cputime.utime;
        dst_bstat->cputime.stime -= src_bstat->cputime.stime;
        dst_bstat->cputime.sum_exec_runtime -= src_bstat->cputime.sum_exec_runtime;
#ifdef CONFIG_SCHED_CORE
        dst_bstat->forceidle_sum -= src_bstat->forceidle_sum;
#endif
        dst_bstat->ntime -= src_bstat->ntime;
}

static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)
{
        struct cgroup_rstat_base_cpu *rstatbc = cgroup_rstat_base_cpu(cgrp, cpu);
        struct cgroup *parent = cgroup_parent(cgrp);
        struct cgroup_rstat_base_cpu *prstatbc;
        struct cgroup_base_stat delta;
        unsigned seq;

        /* Root-level stats are sourced from system-wide CPU stats */
        if (!parent)
                return;

        /* fetch the current per-cpu values */
        do {
                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, &rstatbc->last_bstat);
        cgroup_base_stat_add(&cgrp->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)) {
                delta = cgrp->bstat;
                cgroup_base_stat_sub(&delta, &cgrp->last_bstat);
                cgroup_base_stat_add(&parent->bstat, &delta);
                cgroup_base_stat_add(&cgrp->last_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_base_cpu *
cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
{
        struct cgroup_rstat_base_cpu *rstatbc;

        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_base_cpu *rstatbc,
                                                 unsigned long flags)
{
        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_base_cpu *rstatbc;
        unsigned long 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_base_cpu *rstatbc;
        unsigned long flags;

        rstatbc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);

        switch (index) {
        case CPUTIME_NICE:
                rstatbc->bstat.ntime += delta_exec;
                fallthrough;
        case CPUTIME_USER:
                rstatbc->bstat.cputime.utime += delta_exec;
                break;
        case CPUTIME_SYSTEM:
        case CPUTIME_IRQ:
        case CPUTIME_SOFTIRQ:
                rstatbc->bstat.cputime.stime += delta_exec;
                break;
#ifdef CONFIG_SCHED_CORE
        case CPUTIME_FORCEIDLE:
                rstatbc->bstat.forceidle_sum += delta_exec;
                break;
#endif
        default:
                break;
        }

        cgroup_base_stat_cputime_account_end(cgrp, rstatbc, flags);
}

/*
 * compute the cputime for the root cgroup by getting the per cpu data
 * at a global level, then categorizing the fields in a manner consistent
 * with how it is done by __cgroup_account_cputime_field for each bit of
 * cpu time attributed to a cgroup.
 */
static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
{
        struct task_cputime *cputime = &bstat->cputime;
        int i;

        memset(bstat, 0, sizeof(*bstat));
        for_each_possible_cpu(i) {
                struct kernel_cpustat kcpustat;
                u64 *cpustat = kcpustat.cpustat;
                u64 user = 0;
                u64 sys = 0;

                kcpustat_cpu_fetch(&kcpustat, i);

                user += cpustat[CPUTIME_USER];
                user += cpustat[CPUTIME_NICE];
                cputime->utime += user;

                sys += cpustat[CPUTIME_SYSTEM];
                sys += cpustat[CPUTIME_IRQ];
                sys += cpustat[CPUTIME_SOFTIRQ];
                cputime->stime += sys;

                cputime->sum_exec_runtime += user;
                cputime->sum_exec_runtime += sys;

#ifdef CONFIG_SCHED_CORE
                bstat->forceidle_sum += cpustat[CPUTIME_FORCEIDLE];
#endif
                bstat->ntime += cpustat[CPUTIME_NICE];
        }
}


static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat *bstat)
{
#ifdef CONFIG_SCHED_CORE
        u64 forceidle_time = bstat->forceidle_sum;

        do_div(forceidle_time, NSEC_PER_USEC);
        seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
#endif
}

void cgroup_base_stat_cputime_show(struct seq_file *seq)
{
        struct cgroup *cgrp = seq_css(seq)->cgroup;
        struct cgroup_base_stat bstat;

        if (cgroup_parent(cgrp)) {
                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);
                __css_rstat_unlock(&cgrp->self, -1);
        } else {
                root_cgroup_cputime(&bstat);
        }

        do_div(bstat.cputime.sum_exec_runtime, NSEC_PER_USEC);
        do_div(bstat.cputime.utime, NSEC_PER_USEC);
        do_div(bstat.cputime.stime, NSEC_PER_USEC);
        do_div(bstat.ntime, NSEC_PER_USEC);

        seq_printf(seq, "usage_usec %llu\n"
                        "user_usec %llu\n"
                        "system_usec %llu\n"
                        "nice_usec %llu\n",
                        bstat.cputime.sum_exec_runtime,
                        bstat.cputime.utime,
                        bstat.cputime.stime,
                        bstat.ntime);

        cgroup_force_idle_show(seq, &bstat);
}

/* Add bpf kfuncs for css_rstat_updated() and css_rstat_flush() */
BTF_KFUNCS_START(bpf_rstat_kfunc_ids)
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 = {
        .owner          = THIS_MODULE,
        .set            = &bpf_rstat_kfunc_ids,
};

static int __init bpf_rstat_kfunc_init(void)
{
        return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
                                         &bpf_rstat_kfunc_set);
}
late_initcall(bpf_rstat_kfunc_init);