drm/nouveau: consume the return of large GSP message

[drm/drm-misc.git] / kernel / cgroup / rstat.c

// 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(cgroup_rstat_lock);
static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_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)
{
        return per_cpu_ptr(cgrp->rstat_cpu, cpu);
}

/*
 * Helper functions for rstat per CPU lock (cgroup_rstat_cpu_lock).
 *
 * This makes it easier to diagnose locking issues and contention in
 * production environments. The parameter @fast_path determine the
 * tracepoints being added, allowing us to diagnose "flush" related
 * 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 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.
         */
        contended = !raw_spin_trylock_irqsave(cpu_lock, flags);
        if (contended) {
                if (fast_path)
                        trace_cgroup_rstat_cpu_lock_contended_fastpath(cgrp, cpu, contended);
                else
                        trace_cgroup_rstat_cpu_lock_contended(cgrp, cpu, contended);

                raw_spin_lock_irqsave(cpu_lock, flags);
        }

        if (fast_path)
                trace_cgroup_rstat_cpu_locked_fastpath(cgrp, cpu, contended);
        else
                trace_cgroup_rstat_cpu_locked(cgrp, cpu, contended);

        return flags;
}

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)
{
        if (fast_path)
                trace_cgroup_rstat_cpu_unlock_fastpath(cgrp, cpu, false);
        else
                trace_cgroup_rstat_cpu_unlock(cgrp, cpu, false);

        raw_spin_unlock_irqrestore(cpu_lock, flags);
}

/**
 * cgroup_rstat_updated - keep track of updated rstat_cpu
 * @cgrp: target cgroup
 * @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.
 */
__bpf_kfunc void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)
{
        raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
        unsigned long flags;

        /*
         * 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
         * testing the next pointer for NULL.
         */
        if (data_race(cgroup_rstat_cpu(cgrp, cpu)->updated_next))
                return;

        flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, cgrp, true);

        /* put @cgrp 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;

                /*
                 * 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 = cgrp;
                        break;
                }

                prstatc = cgroup_rstat_cpu(parent, cpu);
                rstatc->updated_next = prstatc->updated_children;
                prstatc->updated_children = cgrp;

                cgrp = parent;
        }

        _cgroup_rstat_cpu_unlock(cpu_lock, cpu, cgrp, flags, true);
}

/**
 * cgroup_rstat_push_children - push children cgroups 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
 *
 * Iteratively traverse down the cgroup_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.
 */
static struct cgroup *cgroup_rstat_push_children(struct cgroup *head,
                                                 struct cgroup *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;

        child->rstat_flush_next = NULL;

next_level:
        while (chead) {
                child = chead;
                chead = child->rstat_flush_next;
                parent = cgroup_parent(child);

                /* updated_next is parent cgroup terminated */
                while (child != parent) {
                        child->rstat_flush_next = head;
                        head = child;
                        crstatc = cgroup_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) {
                chead = ghead;
                ghead = NULL;
                goto next_level;
        }
        return head;
}

/**
 * cgroup_rstat_updated_list - return a list of updated cgroups to be flushed
 * @root: root of the cgroup subtree to traverse
 * @cpu: target cpu
 * Return: A singly linked list of cgroups to be flushed
 *
 * Walks the updated rstat_cpu tree on @cpu from @root.  During traversal,
 * each returned cgroup 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.
 */
static struct cgroup *cgroup_rstat_updated_list(struct cgroup *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;
        unsigned long flags;

        flags = _cgroup_rstat_cpu_lock(cpu_lock, cpu, root, false);

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

        /*
         * 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);
        if (parent) {
                struct cgroup_rstat_cpu *prstatc;
                struct cgroup **nextp;

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

                        nrstatc = cgroup_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 = cgroup_rstat_push_children(head, child, cpu);
unlock_ret:
        _cgroup_rstat_cpu_unlock(cpu_lock, cpu, root, 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
 * 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 cgroup_rstat_lock.
 *
 * 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 __cgroup_rstat_lock(struct cgroup *cgrp, int cpu_in_loop)
        __acquires(&cgroup_rstat_lock)
{
        bool contended;

        contended = !spin_trylock_irq(&cgroup_rstat_lock);
        if (contended) {
                trace_cgroup_rstat_lock_contended(cgrp, cpu_in_loop, contended);
                spin_lock_irq(&cgroup_rstat_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)
{
        trace_cgroup_rstat_unlock(cgrp, cpu_in_loop, false);
        spin_unlock_irq(&cgroup_rstat_lock);
}

/* see cgroup_rstat_flush() */
static void cgroup_rstat_flush_locked(struct cgroup *cgrp)
        __releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
{
        int cpu;

        lockdep_assert_held(&cgroup_rstat_lock);

        for_each_possible_cpu(cpu) {
                struct cgroup *pos = cgroup_rstat_updated_list(cgrp, 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();
                }

                /* play nice and yield if necessary */
                if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
                        __cgroup_rstat_unlock(cgrp, cpu);
                        if (!cond_resched())
                                cpu_relax();
                        __cgroup_rstat_lock(cgrp, cpu);
                }
        }
}

/**
 * cgroup_rstat_flush - flush stats in @cgrp's subtree
 * @cgrp: target cgroup
 *
 * 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.
 *
 * This also gets all cgroups in the subtree including @cgrp off the
 * ->updated_children lists.
 *
 * This function may block.
 */
__bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
{
        might_sleep();

        __cgroup_rstat_lock(cgrp, -1);
        cgroup_rstat_flush_locked(cgrp);
        __cgroup_rstat_unlock(cgrp, -1);
}

/**
 * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
 * @cgrp: target cgroup
 *
 * Flush stats in @cgrp's subtree and prevent further flushes.  Must be
 * paired with cgroup_rstat_flush_release().
 *
 * This function may block.
 */
void cgroup_rstat_flush_hold(struct cgroup *cgrp)
        __acquires(&cgroup_rstat_lock)
{
        might_sleep();
        __cgroup_rstat_lock(cgrp, -1);
        cgroup_rstat_flush_locked(cgrp);
}

/**
 * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
 * @cgrp: cgroup used by tracepoint
 */
void cgroup_rstat_flush_release(struct cgroup *cgrp)
        __releases(&cgroup_rstat_lock)
{
        __cgroup_rstat_unlock(cgrp, -1);
}

int cgroup_rstat_init(struct cgroup *cgrp)
{
        int 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);

                rstatc->updated_children = cgrp;
                u64_stats_init(&rstatc->bsync);
        }

        return 0;
}

void cgroup_rstat_exit(struct cgroup *cgrp)
{
        int cpu;

        cgroup_rstat_flush(cgrp);

        /* sanity check */
        for_each_possible_cpu(cpu) {
                struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);

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

        free_percpu(cgrp->rstat_cpu);
        cgrp->rstat_cpu = NULL;
}

void __init cgroup_rstat_boot(void)
{
        int cpu;

        for_each_possible_cpu(cpu)
                raw_spin_lock_init(per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu));
}

/*
 * 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_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
        struct cgroup *parent = cgroup_parent(cgrp);
        struct cgroup_rstat_cpu *prstatc;
        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(&rstatc->bsync);
                delta = rstatc->bstat;
        } while (__u64_stats_fetch_retry(&rstatc->bsync, seq));

        /* propagate per-cpu delta to cgroup and per-cpu global statistics */
        cgroup_base_stat_sub(&delta, &rstatc->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);

        /* 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 = 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);
        }
}

static struct cgroup_rstat_cpu *
cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp, unsigned long *flags)
{
        struct cgroup_rstat_cpu *rstatc;

        rstatc = get_cpu_ptr(cgrp->rstat_cpu);
        *flags = u64_stats_update_begin_irqsave(&rstatc->bsync);
        return rstatc;
}

static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
                                                 struct cgroup_rstat_cpu *rstatc,
                                                 unsigned long flags)
{
        u64_stats_update_end_irqrestore(&rstatc->bsync, flags);
        cgroup_rstat_updated(cgrp, smp_processor_id());
        put_cpu_ptr(rstatc);
}

void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
{
        struct cgroup_rstat_cpu *rstatc;
        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);
}

void __cgroup_account_cputime_field(struct cgroup *cgrp,
                                    enum cpu_usage_stat index, u64 delta_exec)
{
        struct cgroup_rstat_cpu *rstatc;
        unsigned long flags;

        rstatc = cgroup_base_stat_cputime_account_begin(cgrp, &flags);

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

        cgroup_base_stat_cputime_account_end(cgrp, rstatc, 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;
                cputime->sum_exec_runtime += cpustat[CPUTIME_STEAL];

#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;
        u64 usage, utime, stime, ntime;

        if (cgroup_parent(cgrp)) {
                cgroup_rstat_flush_hold(cgrp);
                usage = cgrp->bstat.cputime.sum_exec_runtime;
                cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
                               &utime, &stime);
                ntime = cgrp->bstat.ntime;
                cgroup_rstat_flush_release(cgrp);
        } else {
                /* cgrp->bstat of root is not actually used, reuse it */
                root_cgroup_cputime(&cgrp->bstat);
                usage = cgrp->bstat.cputime.sum_exec_runtime;
                utime = cgrp->bstat.cputime.utime;
                stime = cgrp->bstat.cputime.stime;
                ntime = cgrp->bstat.ntime;
        }

        do_div(usage, NSEC_PER_USEC);
        do_div(utime, NSEC_PER_USEC);
        do_div(stime, NSEC_PER_USEC);
        do_div(ntime, NSEC_PER_USEC);

        seq_printf(seq, "usage_usec %llu\n"
                        "user_usec %llu\n"
                        "system_usec %llu\n"
                        "nice_usec %llu\n",
                        usage, utime, stime, ntime);

        cgroup_force_idle_show(seq, &cgrp->bstat);
}

/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_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_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);