text: // SPDX-License-Identifier: GPL-2.0
  #include <linux/cgroup.h>
  #include <linux/slab.h>
  #include <linux/percpu.h>
  #include <linux/spinlock.h>
  #include <linux/cpumask.h>
  #include <linux/seq_file.h>
  #include <linux/rcupdate.h>
  #include <linux/kernel_stat.h>
  #include <linux/err.h>
  
  #include "sched.h"
  
  /*
   * CPU accounting code for task groups.
   *
   * Based on the work by Paul Menage (menage@google.com) and Balbir Singh
   * (balbir@in.ibm.com).
   */
  
  /* Time spent by the tasks of the cpu accounting group executing in ... */
  enum cpuacct_stat_index {
  	CPUACCT_STAT_USER,	/* ... user mode */
  	CPUACCT_STAT_SYSTEM,	/* ... kernel mode */
  
  	CPUACCT_STAT_NSTATS,
  };
  
  static const char * const cpuacct_stat_desc[] = {
  	[CPUACCT_STAT_USER] = "user",
  	[CPUACCT_STAT_SYSTEM] = "system",
  };
  
  struct cpuacct_usage {
  	u64	usages[CPUACCT_STAT_NSTATS];
  };
  
  /* track cpu usage of a group of tasks and its child groups */
  struct cpuacct {
  	struct cgroup_subsys_state css;
  	/* cpuusage holds pointer to a u64-type object on every cpu */
  	struct cpuacct_usage __percpu *cpuusage;
  	struct kernel_cpustat __percpu *cpustat;
  };
  
  static inline struct cpuacct *css_ca(struct cgroup_subsys_state *css)
  {
  	return css ? container_of(css, struct cpuacct, css) : NULL;
  }
  
  /* return cpu accounting group to which this task belongs */
  static inline struct cpuacct *task_ca(struct task_struct *tsk)
  {
  	return css_ca(task_css(tsk, cpuacct_cgrp_id));
  }
  
  static inline struct cpuacct *parent_ca(struct cpuacct *ca)
  {
  	return css_ca(ca->css.parent);
  }
  
  static DEFINE_PER_CPU(struct cpuacct_usage, root_cpuacct_cpuusage);
  static struct cpuacct root_cpuacct = {
  	.cpustat	= &kernel_cpustat,
  	.cpuusage	= &root_cpuacct_cpuusage,
  };
  
  /* create a new cpu accounting group */
  static struct cgroup_subsys_state *
  cpuacct_css_alloc(struct cgroup_subsys_state *parent_css)
  {
  	struct cpuacct *ca;
  
  	if (!parent_css)
  		return &root_cpuacct.css;
  
  	ca = kzalloc(sizeof(*ca), GFP_KERNEL);
  	if (!ca)
  		goto out;
  
  	ca->cpuusage = alloc_percpu(struct cpuacct_usage);
  	if (!ca->cpuusage)
  		goto out_free_ca;
  
  	ca->cpustat = alloc_percpu(struct kernel_cpustat);
  	if (!ca->cpustat)
  		goto out_free_cpuusage;
  
  	return &ca->css;
  
  out_free_cpuusage:
  	free_percpu(ca->cpuusage);
  out_free_ca:
  	kfree(ca);
  out:
  	return ERR_PTR(-ENOMEM);
  }
  
  /* destroy an existing cpu accounting group */
  static void cpuacct_css_free(struct cgroup_subsys_state *css)
  {
  	struct cpuacct *ca = css_ca(css);
  
  	free_percpu(ca->cpustat);
  	free_percpu(ca->cpuusage);
  	kfree(ca);
  }
  
  static u64 cpuacct_cpuusage_read(struct cpuacct *ca, int cpu,
  				 enum cpuacct_stat_index index)
  {
  	struct cpuacct_usage *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
  	u64 data;
  
  	/*
  	 * We allow index == CPUACCT_STAT_NSTATS here to read
  	 * the sum of suages.
  	 */
  	BUG_ON(index > CPUACCT_STAT_NSTATS);
  
  #ifndef CONFIG_64BIT
  	/*
  	 * Take rq->lock to make 64-bit read safe on 32-bit platforms.
  	 */
  	raw_spin_lock_irq(&cpu_rq(cpu)->lock);
  #endif
  
  	if (index == CPUACCT_STAT_NSTATS) {
  		int i = 0;
  
  		data = 0;
  		for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
  			data += cpuusage->usages[i];
  	} else {
  		data = cpuusage->usages[index];
  	}
  
  #ifndef CONFIG_64BIT
  	raw_spin_unlock_irq(&cpu_rq(cpu)->lock);
  #endif
  
  	return data;
  }
  
  static void cpuacct_cpuusage_write(struct cpuacct *ca, int cpu, u64 val)
  {
  	struct cpuacct_usage *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
  	int i;
  
  #ifndef CONFIG_64BIT
  	/*
  	 * Take rq->lock to make 64-bit write safe on 32-bit platforms.
  	 */
  	raw_spin_lock_irq(&cpu_rq(cpu)->lock);
  #endif
  
  	for (i = 0; i < CPUACCT_STAT_NSTATS; i++)
  		cpuusage->usages[i] = val;
  
  #ifndef CONFIG_64BIT
  	raw_spin_unlock_irq(&cpu_rq(cpu)->lock);
  #endif
  }
  
  /* return total cpu usage (in nanoseconds) of a group */
  static u64 __cpuusage_read(struct cgroup_subsys_state *css,
  			   enum cpuacct_stat_index index)
  {
  	struct cpuacct *ca = css_ca(css);
  	u64 totalcpuusage = 0;
  	int i;
  
  	for_each_possible_cpu(i)
  		totalcpuusage += cpuacct_cpuusage_read(ca, i, index);
  
  	return totalcpuusage;
  }
  
  static u64 cpuusage_user_read(struct cgroup_subsys_state *css,
  			      struct cftype *cft)
  {
  	return __cpuusage_read(css, CPUACCT_STAT_USER);
  }
  
  static u64 cpuusage_sys_read(struct cgroup_subsys_state *css,
  			     struct cftype *cft)
  {
  	return __cpuusage_read(css, CPUACCT_STAT_SYSTEM);
  }
  
  static u64 cpuusage_read(struct cgroup_subsys_state *css, struct cftype *cft)
  {
  	return __cpuusage_read(css, CPUACCT_STAT_NSTATS);
  }
  
  static int cpuusage_write(struct cgroup_subsys_state *css, struct cftype *cft,
  			  u64 val)
  {
  	struct cpuacct *ca = css_ca(css);
  	int cpu;
  
  	/*
  	 * Only allow '0' here to do a reset.
  	 */
  	if (val)
  		return -EINVAL;
  
  	for_each_possible_cpu(cpu)
  		cpuacct_cpuusage_write(ca, cpu, 0);
  
  	return 0;
  }
  
  static int __cpuacct_percpu_seq_show(struct seq_file *m,
  				     enum cpuacct_stat_index index)
  {
  	struct cpuacct *ca = css_ca(seq_css(m));
  	u64 percpu;
  	int i;
  
  	for_each_possible_cpu(i) {
  		percpu = cpuacct_cpuusage_read(ca, i, index);
  		seq_printf(m, "%llu ", (unsigned long long) percpu);
  	}
  	seq_printf(m, "\n");
  	return 0;
  }
  
  static int cpuacct_percpu_user_seq_show(struct seq_file *m, void *V)
  {
  	return __cpuacct_percpu_seq_show(m, CPUACCT_STAT_USER);
  }
  
  static int cpuacct_percpu_sys_seq_show(struct seq_file *m, void *V)
  {
  	return __cpuacct_percpu_seq_show(m, CPUACCT_STAT_SYSTEM);
  }
  
  static int cpuacct_percpu_seq_show(struct seq_file *m, void *V)
  {
  	return __cpuacct_percpu_seq_show(m, CPUACCT_STAT_NSTATS);
  }
  
  static int cpuacct_all_seq_show(struct seq_file *m, void *V)
  {
  	struct cpuacct *ca = css_ca(seq_css(m));
  	int index;
  	int cpu;
  
  	seq_puts(m, "cpu");
  	for (index = 0; index < CPUACCT_STAT_NSTATS; index++)
  		seq_printf(m, " %s", cpuacct_stat_desc[index]);
  	seq_puts(m, "\n");
  
  	for_each_possible_cpu(cpu) {
  		struct cpuacct_usage *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
  
  		seq_printf(m, "%d", cpu);
  
  		for (index = 0; index < CPUACCT_STAT_NSTATS; index++) {
  #ifndef CONFIG_64BIT
  			/*
  			 * Take rq->lock to make 64-bit read safe on 32-bit
  			 * platforms.
  			 */
  			raw_spin_lock_irq(&cpu_rq(cpu)->lock);
  #endif
  
  			seq_printf(m, " %llu", cpuusage->usages[index]);
  
  #ifndef CONFIG_64BIT
  			raw_spin_unlock_irq(&cpu_rq(cpu)->lock);
  #endif
  		}
  		seq_puts(m, "\n");
  	}
  	return 0;
  }
  
  static int cpuacct_stats_show(struct seq_file *sf, void *v)
  {
  	struct cpuacct *ca = css_ca(seq_css(sf));
  	s64 val[CPUACCT_STAT_NSTATS];
  	int cpu;
  	int stat;
  
  	memset(val, 0, sizeof(val));
  	for_each_possible_cpu(cpu) {
  		u64 *cpustat = per_cpu_ptr(ca->cpustat, cpu)->cpustat;
  
  		val[CPUACCT_STAT_USER]   += cpustat[CPUTIME_USER];
  		val[CPUACCT_STAT_USER]   += cpustat[CPUTIME_NICE];
  		val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_SYSTEM];
  		val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_IRQ];
  		val[CPUACCT_STAT_SYSTEM] += cpustat[CPUTIME_SOFTIRQ];
  	}
  
  	for (stat = 0; stat < CPUACCT_STAT_NSTATS; stat++) {
  		seq_printf(sf, "%s %lld\n",
  			   cpuacct_stat_desc[stat],
  			   (long long)nsec_to_clock_t(val[stat]));
  	}
  
  	return 0;
  }
  
  static struct cftype files[] = {
  	{
  		.name = "usage",
  		.read_u64 = cpuusage_read,
  		.write_u64 = cpuusage_write,
  	},
  	{
  		.name = "usage_user",
  		.read_u64 = cpuusage_user_read,
  	},
  	{
  		.name = "usage_sys",
  		.read_u64 = cpuusage_sys_read,
  	},
  	{
  		.name = "usage_percpu",
  		.seq_show = cpuacct_percpu_seq_show,
  	},
  	{
  		.name = "usage_percpu_user",
  		.seq_show = cpuacct_percpu_user_seq_show,
  	},
  	{
  		.name = "usage_percpu_sys",
  		.seq_show = cpuacct_percpu_sys_seq_show,
  	},
  	{
  		.name = "usage_all",
  		.seq_show = cpuacct_all_seq_show,
  	},
  	{
  		.name = "stat",
  		.seq_show = cpuacct_stats_show,
  	},
  	{ }	/* terminate */
  };
  
  /*
   * charge this task's execution time to its accounting group.
   *
   * called with rq->lock held.
   */
  void cpuacct_charge(struct task_struct *tsk, u64 cputime)
  {
  	struct cpuacct *ca;
  	int index = CPUACCT_STAT_SYSTEM;
  	struct pt_regs *regs = task_pt_regs(tsk);
  
  	if (regs && user_mode(regs))
  		index = CPUACCT_STAT_USER;
  
  	rcu_read_lock();
  
  	for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
  		this_cpu_ptr(ca->cpuusage)->usages[index] += cputime;
  
  	rcu_read_unlock();
  }
  
  /*
   * Add user/system time to cpuacct.
   *
   * Note: it's the caller that updates the account of the root cgroup.
   */
  void cpuacct_account_field(struct task_struct *tsk, int index, u64 val)
  {
  	struct cpuacct *ca;
  
  	rcu_read_lock();
  	for (ca = task_ca(tsk); ca != &root_cpuacct; ca = parent_ca(ca))
  		this_cpu_ptr(ca->cpustat)->cpustat[index] += val;
  	rcu_read_unlock();
  }
  
  struct cgroup_subsys cpuacct_cgrp_subsys = {
  	.css_alloc	= cpuacct_css_alloc,
  	.css_free	= cpuacct_css_free,
  	.legacy_cftypes	= files,
  	.early_init	= true,
  };
  