/* delayacct.c - per-task delay accounting
   *
   * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   *
   * This program is free software;  you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it would be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
   * the GNU General Public License for more details.
   */
  
  #include <linux/sched.h>

  #include <linux/sched/task.h>

  #include <linux/sched/cputime.h>

  #include <linux/slab.h>

  #include <linux/taskstats.h>

  #include <linux/time.h>
  #include <linux/sysctl.h>
  #include <linux/delayacct.h>

  #include <linux/module.h>

  int delayacct_on __read_mostly = 1;	/* Delay accounting turned on/off */

  EXPORT_SYMBOL_GPL(delayacct_on);

  struct kmem_cache *delayacct_cache;

  static int __init delayacct_setup_disable(char *str)

  {

  	delayacct_on = 0;

  	return 1;
  }

  __setup("nodelayacct", delayacct_setup_disable);

  
  void delayacct_init(void)
  {

  	delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);

  	delayacct_tsk_init(&init_task);
  }
  
  void __delayacct_tsk_init(struct task_struct *tsk)
  {

  	tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);

  	if (tsk->delays)

  		raw_spin_lock_init(&tsk->delays->lock);

  }

  /*

   * Finish delay accounting for a statistic using its timestamps (@start),
   * accumalator (@total) and @count

   */

  static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total,
  			  u32 *count)

  {

  	s64 ns = ktime_get_ns() - *start;

  	unsigned long flags;

  	if (ns > 0) {

  		raw_spin_lock_irqsave(lock, flags);

  		*total += ns;
  		(*count)++;

  		raw_spin_unlock_irqrestore(lock, flags);

  	}

  }

  void __delayacct_blkio_start(void)
  {

  	current->delays->blkio_start = ktime_get_ns();

  }

  /*
   * We cannot rely on the `current` macro, as we haven't yet switched back to
   * the process being woken.
   */
  void __delayacct_blkio_end(struct task_struct *p)

  {

  	struct task_delay_info *delays = p->delays;
  	u64 *total;
  	u32 *count;
  
  	if (p->delays->flags & DELAYACCT_PF_SWAPIN) {
  		total = &delays->swapin_delay;
  		count = &delays->swapin_count;
  	} else {
  		total = &delays->blkio_delay;
  		count = &delays->blkio_count;
  	}
  
  	delayacct_end(&delays->lock, &delays->blkio_start, total, count);

  }

  
  int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
  {

  	u64 utime, stime, stimescaled, utimescaled;

  	unsigned long long t2, t3;
  	unsigned long flags, t1;
  	s64 tmp;

  	task_cputime(tsk, &utime, &stime);

  	tmp = (s64)d->cpu_run_real_total;

  	tmp += utime + stime;

  	d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;

  	task_cputime_scaled(tsk, &utimescaled, &stimescaled);

  	tmp = (s64)d->cpu_scaled_run_real_total;

  	tmp += utimescaled + stimescaled;

  	d->cpu_scaled_run_real_total =
  		(tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;

  	/*
  	 * No locking available for sched_info (and too expensive to add one)
  	 * Mitigate by taking snapshot of values
  	 */

  	t1 = tsk->sched_info.pcount;

  	t2 = tsk->sched_info.run_delay;

  	t3 = tsk->se.sum_exec_runtime;

  
  	d->cpu_count += t1;

  	tmp = (s64)d->cpu_delay_total + t2;

  	d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;

  	tmp = (s64)d->cpu_run_virtual_total + t3;

  	d->cpu_run_virtual_total =
  		(tmp < (s64)d->cpu_run_virtual_total) ?	0 : tmp;
  
  	/* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */

  	raw_spin_lock_irqsave(&tsk->delays->lock, flags);

  	tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
  	d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
  	tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
  	d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;

  	tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
  	d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;

  	d->blkio_count += tsk->delays->blkio_count;
  	d->swapin_count += tsk->delays->swapin_count;

  	d->freepages_count += tsk->delays->freepages_count;

  	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);

  	return 0;
  }

  
  __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
  {
  	__u64 ret;

  	unsigned long flags;

  	raw_spin_lock_irqsave(&tsk->delays->lock, flags);

  	ret = nsec_to_clock_t(tsk->delays->blkio_delay +
  				tsk->delays->swapin_delay);

  	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);

  	return ret;
  }

  void __delayacct_freepages_start(void)
  {

  	current->delays->freepages_start = ktime_get_ns();

  }
  
  void __delayacct_freepages_end(void)
  {

  	delayacct_end(
  		&current->delays->lock,
  		&current->delays->freepages_start,
  		&current->delays->freepages_delay,
  		&current->delays->freepages_count);

  }