// SPDX-License-Identifier: GPL-2.0-only

  #include "cgroup-internal.h"
  
  #include <linux/sched/cputime.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);

  }
  
  /**

   * 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.

   */

  void cgroup_rstat_updated(struct cgroup *cgrp, int cpu)

  {

  	raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);

  	struct cgroup *parent;
  	unsigned long flags;

  	/* nothing to do for root */
  	if (!cgroup_parent(cgrp))
  		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
  	 * testing the next pointer for NULL.
  	 */

  	if (cgroup_rstat_cpu(cgrp, cpu)->updated_next)

  		return;
  
  	raw_spin_lock_irqsave(cpu_lock, flags);
  
  	/* put @cgrp and all ancestors on the corresponding updated lists */
  	for (parent = cgroup_parent(cgrp); parent;
  	     cgrp = parent, parent = cgroup_parent(cgrp)) {

  		struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);
  		struct cgroup_rstat_cpu *prstatc = cgroup_rstat_cpu(parent, cpu);

  
  		/*
  		 * Both additions and removals are bottom-up.  If a cgroup
  		 * is already in the tree, all ancestors are.
  		 */

  		if (rstatc->updated_next)

  			break;

  		rstatc->updated_next = prstatc->updated_children;
  		prstatc->updated_children = cgrp;

  	}
  
  	raw_spin_unlock_irqrestore(cpu_lock, flags);
  }
  
  /**

   * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree

   * @pos: current position
   * @root: root of the tree to traversal
   * @cpu: target cpu
   *

   * Walks the udpated rstat_cpu tree on @cpu from @root.  %NULL @pos starts

   * the traversal and %NULL return indicates the end.  During traversal,
   * each returned cgroup is unlinked from the tree.  Must be called with the

   * matching cgroup_rstat_cpu_lock held.

   *
   * The only ordering guarantee is that, for a parent and a child pair
   * covered by a given traversal, if a child is visited, its parent is
   * guaranteed to be visited afterwards.
   */

  static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
  						   struct cgroup *root, int cpu)

  {

  	struct cgroup_rstat_cpu *rstatc;

  
  	if (pos == root)
  		return NULL;
  
  	/*
  	 * We're gonna walk down to the first leaf and visit/remove it.  We
  	 * can pick whatever unvisited node as the starting point.
  	 */
  	if (!pos)
  		pos = root;
  	else
  		pos = cgroup_parent(pos);
  
  	/* walk down to the first leaf */
  	while (true) {

  		rstatc = cgroup_rstat_cpu(pos, cpu);
  		if (rstatc->updated_children == pos)

  			break;

  		pos = rstatc->updated_children;

  	}
  
  	/*
  	 * Unlink @pos from the tree.  As the updated_children list is
  	 * singly linked, we have to walk it to find the removal point.
  	 * However, due to the way we traverse, @pos will be the first
  	 * child in most cases. The only exception is @root.
  	 */

  	if (rstatc->updated_next) {
  		struct cgroup *parent = cgroup_parent(pos);

  		struct cgroup_rstat_cpu *prstatc = cgroup_rstat_cpu(parent, cpu);
  		struct cgroup_rstat_cpu *nrstatc;

  		struct cgroup **nextp;

  		nextp = &prstatc->updated_children;

  		while (true) {

  			nrstatc = cgroup_rstat_cpu(*nextp, cpu);

  			if (*nextp == pos)
  				break;
  
  			WARN_ON_ONCE(*nextp == parent);

  			nextp = &nrstatc->updated_next;

  		}

  		*nextp = rstatc->updated_next;
  		rstatc->updated_next = NULL;

  		return pos;

  	}

  	/* only happens for @root */
  	return NULL;

  }

  /* see cgroup_rstat_flush() */

  static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
  	__releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)

  {
  	int cpu;

  	lockdep_assert_held(&cgroup_rstat_lock);

  
  	for_each_possible_cpu(cpu) {
  		raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock,
  						       cpu);
  		struct cgroup *pos = NULL;

  		raw_spin_lock(cpu_lock);

  		while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) {
  			struct cgroup_subsys_state *css;

  			cgroup_base_stat_flush(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();
  		}

  		raw_spin_unlock(cpu_lock);
  
  		/* if @may_sleep, play nice and yield if necessary */
  		if (may_sleep && (need_resched() ||
  				  spin_needbreak(&cgroup_rstat_lock))) {
  			spin_unlock_irq(&cgroup_rstat_lock);
  			if (!cond_resched())
  				cpu_relax();
  			spin_lock_irq(&cgroup_rstat_lock);
  		}

  	}
  }
  
  /**
   * 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.

   */
  void cgroup_rstat_flush(struct cgroup *cgrp)
  {

  	might_sleep();
  
  	spin_lock_irq(&cgroup_rstat_lock);
  	cgroup_rstat_flush_locked(cgrp, true);
  	spin_unlock_irq(&cgroup_rstat_lock);
  }
  
  /**
   * cgroup_rstat_flush_irqsafe - irqsafe version of cgroup_rstat_flush()
   * @cgrp: target cgroup
   *
   * This function can be called from any context.
   */
  void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&cgroup_rstat_lock, flags);
  	cgroup_rstat_flush_locked(cgrp, false);
  	spin_unlock_irqrestore(&cgroup_rstat_lock, flags);

  }

  /**
   * cgroup_rstat_flush_begin - 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();
  	spin_lock_irq(&cgroup_rstat_lock);
  	cgroup_rstat_flush_locked(cgrp, true);

  }
  
  /**
   * cgroup_rstat_flush_release - release cgroup_rstat_flush_hold()
   */
  void cgroup_rstat_flush_release(void)

  	__releases(&cgroup_rstat_lock)

  {

  	spin_unlock_irq(&cgroup_rstat_lock);

  }

  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));
  
  	BUG_ON(cgroup_rstat_init(&cgrp_dfl_root.cgrp));
  }
  
  /*
   * 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;

  }

  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;
  }

  static void cgroup_base_stat_flush(struct cgroup *cgrp, int cpu)

  {
  	struct cgroup *parent = cgroup_parent(cgrp);

  	struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(cgrp, cpu);

  	struct cgroup_base_stat cur, delta;

  	unsigned seq;

  	/* fetch the current per-cpu values */
  	do {

  		seq = __u64_stats_fetch_begin(&rstatc->bsync);

  		cur.cputime = rstatc->bstat.cputime;

  	} while (__u64_stats_fetch_retry(&rstatc->bsync, seq));

  	/* propagate percpu delta to global */
  	delta = cur;
  	cgroup_base_stat_sub(&delta, &rstatc->last_bstat);
  	cgroup_base_stat_add(&cgrp->bstat, &delta);
  	cgroup_base_stat_add(&rstatc->last_bstat, &delta);
  
  	/* propagate global delta to parent */
  	if (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);
  	}

  }

  static struct cgroup_rstat_cpu *

  cgroup_base_stat_cputime_account_begin(struct cgroup *cgrp)

  {

  	struct cgroup_rstat_cpu *rstatc;

  	rstatc = get_cpu_ptr(cgrp->rstat_cpu);

  	u64_stats_update_begin(&rstatc->bsync);

  	return rstatc;

  }

  static void cgroup_base_stat_cputime_account_end(struct cgroup *cgrp,
  						 struct cgroup_rstat_cpu *rstatc)

  {

  	u64_stats_update_end(&rstatc->bsync);

  	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;

  	rstatc = cgroup_base_stat_cputime_account_begin(cgrp);
  	rstatc->bstat.cputime.sum_exec_runtime += delta_exec;
  	cgroup_base_stat_cputime_account_end(cgrp, rstatc);

  }
  
  void __cgroup_account_cputime_field(struct cgroup *cgrp,
  				    enum cpu_usage_stat index, u64 delta_exec)
  {

  	struct cgroup_rstat_cpu *rstatc;

  	rstatc = cgroup_base_stat_cputime_account_begin(cgrp);

  
  	switch (index) {
  	case CPUTIME_USER:
  	case CPUTIME_NICE:

  		rstatc->bstat.cputime.utime += delta_exec;

  		break;
  	case CPUTIME_SYSTEM:
  	case CPUTIME_IRQ:
  	case CPUTIME_SOFTIRQ:

  		rstatc->bstat.cputime.stime += delta_exec;

  		break;
  	default:
  		break;
  	}

  	cgroup_base_stat_cputime_account_end(cgrp, rstatc);

  }

  /*
   * 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 task_cputime *cputime)
  {
  	int i;
  
  	cputime->stime = 0;
  	cputime->utime = 0;
  	cputime->sum_exec_runtime = 0;
  	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];
  		cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST];
  		cputime->sum_exec_runtime += cpustat[CPUTIME_GUEST_NICE];
  	}
  }

  void cgroup_base_stat_cputime_show(struct seq_file *seq)

  {
  	struct cgroup *cgrp = seq_css(seq)->cgroup;
  	u64 usage, utime, stime;

  	struct task_cputime cputime;
  
  	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);
  		cgroup_rstat_flush_release();
  	} else {
  		root_cgroup_cputime(&cputime);
  		usage = cputime.sum_exec_runtime;
  		utime = cputime.utime;
  		stime = cputime.stime;
  	}

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

  	seq_printf(seq, "usage_usec %llu
  "
  		   "user_usec %llu
  "
  		   "system_usec %llu
  ",
  		   usage, utime, stime);

  }