#include <linux/export.h>
  #include <linux/sched.h>
  #include <linux/tsacct_kern.h>
  #include <linux/kernel_stat.h>
  #include <linux/static_key.h>

  #include <linux/context_tracking.h>

  #include "sched.h"
  
  
  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  
  /*
   * There are no locks covering percpu hardirq/softirq time.

   * They are only modified in vtime_account, on corresponding CPU

   * with interrupts disabled. So, writes are safe.
   * They are read and saved off onto struct rq in update_rq_clock().
   * This may result in other CPU reading this CPU's irq time and can

   * race with irq/vtime_account on this CPU. We would either get old

   * or new value with a side effect of accounting a slice of irq time to wrong
   * task when irq is in progress while we read rq->clock. That is a worthy
   * compromise in place of having locks on each irq in account_system_time.
   */
  DEFINE_PER_CPU(u64, cpu_hardirq_time);
  DEFINE_PER_CPU(u64, cpu_softirq_time);
  
  static DEFINE_PER_CPU(u64, irq_start_time);
  static int sched_clock_irqtime;
  
  void enable_sched_clock_irqtime(void)
  {
  	sched_clock_irqtime = 1;
  }
  
  void disable_sched_clock_irqtime(void)
  {
  	sched_clock_irqtime = 0;
  }
  
  #ifndef CONFIG_64BIT
  DEFINE_PER_CPU(seqcount_t, irq_time_seq);
  #endif /* CONFIG_64BIT */
  
  /*
   * Called before incrementing preempt_count on {soft,}irq_enter
   * and before decrementing preempt_count on {soft,}irq_exit.
   */

  void irqtime_account_irq(struct task_struct *curr)

  {
  	unsigned long flags;
  	s64 delta;
  	int cpu;
  
  	if (!sched_clock_irqtime)
  		return;
  
  	local_irq_save(flags);
  
  	cpu = smp_processor_id();
  	delta = sched_clock_cpu(cpu) - __this_cpu_read(irq_start_time);
  	__this_cpu_add(irq_start_time, delta);
  
  	irq_time_write_begin();
  	/*
  	 * We do not account for softirq time from ksoftirqd here.
  	 * We want to continue accounting softirq time to ksoftirqd thread
  	 * in that case, so as not to confuse scheduler with a special task
  	 * that do not consume any time, but still wants to run.
  	 */
  	if (hardirq_count())
  		__this_cpu_add(cpu_hardirq_time, delta);
  	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
  		__this_cpu_add(cpu_softirq_time, delta);
  
  	irq_time_write_end();
  	local_irq_restore(flags);
  }

  EXPORT_SYMBOL_GPL(irqtime_account_irq);

  
  static int irqtime_account_hi_update(void)
  {
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  	unsigned long flags;
  	u64 latest_ns;
  	int ret = 0;
  
  	local_irq_save(flags);
  	latest_ns = this_cpu_read(cpu_hardirq_time);
  	if (nsecs_to_cputime64(latest_ns) > cpustat[CPUTIME_IRQ])
  		ret = 1;
  	local_irq_restore(flags);
  	return ret;
  }
  
  static int irqtime_account_si_update(void)
  {
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  	unsigned long flags;
  	u64 latest_ns;
  	int ret = 0;
  
  	local_irq_save(flags);
  	latest_ns = this_cpu_read(cpu_softirq_time);
  	if (nsecs_to_cputime64(latest_ns) > cpustat[CPUTIME_SOFTIRQ])
  		ret = 1;
  	local_irq_restore(flags);
  	return ret;
  }
  
  #else /* CONFIG_IRQ_TIME_ACCOUNTING */
  
  #define sched_clock_irqtime	(0)
  
  #endif /* !CONFIG_IRQ_TIME_ACCOUNTING */
  
  static inline void task_group_account_field(struct task_struct *p, int index,
  					    u64 tmp)
  {

  	/*
  	 * Since all updates are sure to touch the root cgroup, we
  	 * get ourselves ahead and touch it first. If the root cgroup
  	 * is the only cgroup, then nothing else should be necessary.
  	 *
  	 */
  	__get_cpu_var(kernel_cpustat).cpustat[index] += tmp;

  	cpuacct_account_field(p, index, tmp);

  }
  
  /*
   * Account user cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in user space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  void account_user_time(struct task_struct *p, cputime_t cputime,
  		       cputime_t cputime_scaled)
  {
  	int index;
  
  	/* Add user time to process. */
  	p->utime += cputime;
  	p->utimescaled += cputime_scaled;
  	account_group_user_time(p, cputime);
  
  	index = (TASK_NICE(p) > 0) ? CPUTIME_NICE : CPUTIME_USER;
  
  	/* Add user time to cpustat. */
  	task_group_account_field(p, index, (__force u64) cputime);
  
  	/* Account for user time used */

  	acct_account_cputime(p);

  }
  
  /*
   * Account guest cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in virtual machine since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  static void account_guest_time(struct task_struct *p, cputime_t cputime,
  			       cputime_t cputime_scaled)
  {
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  
  	/* Add guest time to process. */
  	p->utime += cputime;
  	p->utimescaled += cputime_scaled;
  	account_group_user_time(p, cputime);
  	p->gtime += cputime;
  
  	/* Add guest time to cpustat. */
  	if (TASK_NICE(p) > 0) {
  		cpustat[CPUTIME_NICE] += (__force u64) cputime;
  		cpustat[CPUTIME_GUEST_NICE] += (__force u64) cputime;
  	} else {
  		cpustat[CPUTIME_USER] += (__force u64) cputime;
  		cpustat[CPUTIME_GUEST] += (__force u64) cputime;
  	}
  }
  
  /*
   * Account system cpu time to a process and desired cpustat field
   * @p: the process that the cpu time gets accounted to
   * @cputime: the cpu time spent in kernel space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   * @target_cputime64: pointer to cpustat field that has to be updated
   */
  static inline
  void __account_system_time(struct task_struct *p, cputime_t cputime,
  			cputime_t cputime_scaled, int index)
  {
  	/* Add system time to process. */
  	p->stime += cputime;
  	p->stimescaled += cputime_scaled;
  	account_group_system_time(p, cputime);
  
  	/* Add system time to cpustat. */
  	task_group_account_field(p, index, (__force u64) cputime);
  
  	/* Account for system time used */

  	acct_account_cputime(p);

  }
  
  /*
   * Account system cpu time to a process.
   * @p: the process that the cpu time gets accounted to
   * @hardirq_offset: the offset to subtract from hardirq_count()
   * @cputime: the cpu time spent in kernel space since the last update
   * @cputime_scaled: cputime scaled by cpu frequency
   */
  void account_system_time(struct task_struct *p, int hardirq_offset,
  			 cputime_t cputime, cputime_t cputime_scaled)
  {
  	int index;
  
  	if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
  		account_guest_time(p, cputime, cputime_scaled);
  		return;
  	}
  
  	if (hardirq_count() - hardirq_offset)
  		index = CPUTIME_IRQ;
  	else if (in_serving_softirq())
  		index = CPUTIME_SOFTIRQ;
  	else
  		index = CPUTIME_SYSTEM;
  
  	__account_system_time(p, cputime, cputime_scaled, index);
  }
  
  /*
   * Account for involuntary wait time.
   * @cputime: the cpu time spent in involuntary wait
   */
  void account_steal_time(cputime_t cputime)
  {
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  
  	cpustat[CPUTIME_STEAL] += (__force u64) cputime;
  }
  
  /*
   * Account for idle time.
   * @cputime: the cpu time spent in idle wait
   */
  void account_idle_time(cputime_t cputime)
  {
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  	struct rq *rq = this_rq();
  
  	if (atomic_read(&rq->nr_iowait) > 0)
  		cpustat[CPUTIME_IOWAIT] += (__force u64) cputime;
  	else
  		cpustat[CPUTIME_IDLE] += (__force u64) cputime;
  }
  
  static __always_inline bool steal_account_process_tick(void)
  {
  #ifdef CONFIG_PARAVIRT
  	if (static_key_false(&paravirt_steal_enabled)) {
  		u64 steal, st = 0;
  
  		steal = paravirt_steal_clock(smp_processor_id());
  		steal -= this_rq()->prev_steal_time;
  
  		st = steal_ticks(steal);
  		this_rq()->prev_steal_time += st * TICK_NSEC;
  
  		account_steal_time(st);
  		return st;
  	}
  #endif
  	return false;
  }

  /*
   * Accumulate raw cputime values of dead tasks (sig->[us]time) and live
   * tasks (sum on group iteration) belonging to @tsk's group.
   */
  void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
  {
  	struct signal_struct *sig = tsk->signal;

  	cputime_t utime, stime;

  	struct task_struct *t;
  
  	times->utime = sig->utime;
  	times->stime = sig->stime;
  	times->sum_exec_runtime = sig->sum_sched_runtime;
  
  	rcu_read_lock();
  	/* make sure we can trust tsk->thread_group list */
  	if (!likely(pid_alive(tsk)))
  		goto out;
  
  	t = tsk;
  	do {

  		task_cputime(t, &utime, &stime);

  		times->utime += utime;
  		times->stime += stime;

  		times->sum_exec_runtime += task_sched_runtime(t);
  	} while_each_thread(tsk, t);
  out:
  	rcu_read_unlock();
  }

  #ifdef CONFIG_IRQ_TIME_ACCOUNTING
  /*
   * Account a tick to a process and cpustat
   * @p: the process that the cpu time gets accounted to
   * @user_tick: is the tick from userspace
   * @rq: the pointer to rq
   *
   * Tick demultiplexing follows the order
   * - pending hardirq update
   * - pending softirq update
   * - user_time
   * - idle_time
   * - system time
   *   - check for guest_time
   *   - else account as system_time
   *
   * Check for hardirq is done both for system and user time as there is
   * no timer going off while we are on hardirq and hence we may never get an
   * opportunity to update it solely in system time.
   * p->stime and friends are only updated on system time and not on irq
   * softirq as those do not count in task exec_runtime any more.
   */
  static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
  						struct rq *rq)
  {
  	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
  	u64 *cpustat = kcpustat_this_cpu->cpustat;
  
  	if (steal_account_process_tick())
  		return;
  
  	if (irqtime_account_hi_update()) {
  		cpustat[CPUTIME_IRQ] += (__force u64) cputime_one_jiffy;
  	} else if (irqtime_account_si_update()) {
  		cpustat[CPUTIME_SOFTIRQ] += (__force u64) cputime_one_jiffy;
  	} else if (this_cpu_ksoftirqd() == p) {
  		/*
  		 * ksoftirqd time do not get accounted in cpu_softirq_time.
  		 * So, we have to handle it separately here.
  		 * Also, p->stime needs to be updated for ksoftirqd.
  		 */
  		__account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
  					CPUTIME_SOFTIRQ);
  	} else if (user_tick) {
  		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
  	} else if (p == rq->idle) {
  		account_idle_time(cputime_one_jiffy);
  	} else if (p->flags & PF_VCPU) { /* System time or guest time */
  		account_guest_time(p, cputime_one_jiffy, one_jiffy_scaled);
  	} else {
  		__account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
  					CPUTIME_SYSTEM);
  	}
  }
  
  static void irqtime_account_idle_ticks(int ticks)
  {
  	int i;
  	struct rq *rq = this_rq();
  
  	for (i = 0; i < ticks; i++)
  		irqtime_account_process_tick(current, 0, rq);
  }
  #else /* CONFIG_IRQ_TIME_ACCOUNTING */

  static inline void irqtime_account_idle_ticks(int ticks) {}
  static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,

  						struct rq *rq) {}
  #endif /* CONFIG_IRQ_TIME_ACCOUNTING */

  /*
   * Use precise platform statistics if available:
   */
  #ifdef CONFIG_VIRT_CPU_ACCOUNTING

  #ifndef __ARCH_HAS_VTIME_TASK_SWITCH
  void vtime_task_switch(struct task_struct *prev)
  {

  	if (!vtime_accounting_enabled())
  		return;

  	if (is_idle_task(prev))
  		vtime_account_idle(prev);
  	else
  		vtime_account_system(prev);

  #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE

  	vtime_account_user(prev);

  #endif

  	arch_vtime_task_switch(prev);
  }
  #endif

  /*
   * Archs that account the whole time spent in the idle task
   * (outside irq) as idle time can rely on this and just implement

   * vtime_account_system() and vtime_account_idle(). Archs that

   * have other meaning of the idle time (s390 only includes the
   * time spent by the CPU when it's in low power mode) must override
   * vtime_account().
   */
  #ifndef __ARCH_HAS_VTIME_ACCOUNT

  void vtime_account_irq_enter(struct task_struct *tsk)

  {

  	if (!vtime_accounting_enabled())
  		return;

  	if (!in_interrupt()) {
  		/*
  		 * If we interrupted user, context_tracking_in_user()
  		 * is 1 because the context tracking don't hook
  		 * on irq entry/exit. This way we know if
  		 * we need to flush user time on kernel entry.
  		 */
  		if (context_tracking_in_user()) {
  			vtime_account_user(tsk);
  			return;
  		}
  
  		if (is_idle_task(tsk)) {
  			vtime_account_idle(tsk);
  			return;
  		}
  	}
  	vtime_account_system(tsk);

  }

  EXPORT_SYMBOL_GPL(vtime_account_irq_enter);

  #endif /* __ARCH_HAS_VTIME_ACCOUNT */

  #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
  
  
  #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
  void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
  	*ut = p->utime;
  	*st = p->stime;
  }

  void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
  	struct task_cputime cputime;

  	thread_group_cputime(p, &cputime);
  
  	*ut = cputime.utime;
  	*st = cputime.stime;
  }
  #else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
  /*
   * Account a single tick of cpu time.
   * @p: the process that the cpu time gets accounted to
   * @user_tick: indicates if the tick is a user or a system tick
   */
  void account_process_tick(struct task_struct *p, int user_tick)

  {

  	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
  	struct rq *rq = this_rq();

  	if (vtime_accounting_enabled())
  		return;
  
  	if (sched_clock_irqtime) {
  		irqtime_account_process_tick(p, user_tick, rq);
  		return;
  	}
  
  	if (steal_account_process_tick())
  		return;

  	if (user_tick)
  		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
  	else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
  		account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
  				    one_jiffy_scaled);

  	else

  		account_idle_time(cputime_one_jiffy);
  }

  /*
   * Account multiple ticks of steal time.
   * @p: the process from which the cpu time has been stolen
   * @ticks: number of stolen ticks
   */
  void account_steal_ticks(unsigned long ticks)
  {
  	account_steal_time(jiffies_to_cputime(ticks));
  }
  
  /*
   * Account multiple ticks of idle time.
   * @ticks: number of stolen ticks
   */
  void account_idle_ticks(unsigned long ticks)
  {
  
  	if (sched_clock_irqtime) {
  		irqtime_account_idle_ticks(ticks);
  		return;
  	}
  
  	account_idle_time(jiffies_to_cputime(ticks));
  }

  /*

   * Perform (stime * rtime) / total, but avoid multiplication overflow by
   * loosing precision when the numbers are big.

   */
  static cputime_t scale_stime(u64 stime, u64 rtime, u64 total)

  {

  	u64 scaled;

  	for (;;) {
  		/* Make sure "rtime" is the bigger of stime/rtime */
  		if (stime > rtime) {
  			u64 tmp = rtime; rtime = stime; stime = tmp;
  		}
  
  		/* Make sure 'total' fits in 32 bits */
  		if (total >> 32)
  			goto drop_precision;
  
  		/* Does rtime (and thus stime) fit in 32 bits? */
  		if (!(rtime >> 32))
  			break;
  
  		/* Can we just balance rtime/stime rather than dropping bits? */
  		if (stime >> 31)
  			goto drop_precision;
  
  		/* We can grow stime and shrink rtime and try to make them both fit */
  		stime <<= 1;
  		rtime >>= 1;
  		continue;
  
  drop_precision:
  		/* We drop from rtime, it has more bits than stime */
  		rtime >>= 1;
  		total >>= 1;

  	}

  	/*
  	 * Make sure gcc understands that this is a 32x32->64 multiply,
  	 * followed by a 64/32->64 divide.
  	 */
  	scaled = div_u64((u64) (u32) stime * (u64) (u32) rtime, (u32)total);

  	return (__force cputime_t) scaled;

  }

  /*
   * Adjust tick based cputime random precision against scheduler
   * runtime accounting.
   */

  static void cputime_adjust(struct task_cputime *curr,
  			   struct cputime *prev,
  			   cputime_t *ut, cputime_t *st)

  {

  	cputime_t rtime, stime, utime;

  	if (vtime_accounting_enabled()) {
  		*ut = curr->utime;
  		*st = curr->stime;
  		return;
  	}

  	/*

  	 * Tick based cputime accounting depend on random scheduling
  	 * timeslices of a task to be interrupted or not by the timer.
  	 * Depending on these circumstances, the number of these interrupts
  	 * may be over or under-optimistic, matching the real user and system
  	 * cputime with a variable precision.
  	 *
  	 * Fix this by scaling these tick based values against the total
  	 * runtime accounted by the CFS scheduler.

  	 */

  	rtime = nsecs_to_cputime(curr->sum_exec_runtime);

  	/*
  	 * Update userspace visible utime/stime values only if actual execution
  	 * time is bigger than already exported. Note that can happen, that we
  	 * provided bigger values due to scaling inaccuracy on big numbers.
  	 */
  	if (prev->stime + prev->utime >= rtime)
  		goto out;

  	stime = curr->stime;
  	utime = curr->utime;
  
  	if (utime == 0) {
  		stime = rtime;
  	} else if (stime == 0) {
  		utime = rtime;
  	} else {
  		cputime_t total = stime + utime;

  		stime = scale_stime((__force u64)stime,
  				    (__force u64)rtime, (__force u64)total);

  		utime = rtime - stime;

  	}

  
  	/*

  	 * If the tick based count grows faster than the scheduler one,
  	 * the result of the scaling may go backward.
  	 * Let's enforce monotonicity.

  	 */

  	prev->stime = max(prev->stime, stime);

  	prev->utime = max(prev->utime, utime);

  out:

  	*ut = prev->utime;
  	*st = prev->stime;
  }

  void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
  {
  	struct task_cputime cputime = {

  		.sum_exec_runtime = p->se.sum_exec_runtime,
  	};

  	task_cputime(p, &cputime.utime, &cputime.stime);

  	cputime_adjust(&cputime, &p->prev_cputime, ut, st);

  }
  
  /*
   * Must be called with siglock held.
   */

  void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)

  {

  	struct task_cputime cputime;

  
  	thread_group_cputime(p, &cputime);

  	cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);

  }

  #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

  
  #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN

  static unsigned long long vtime_delta(struct task_struct *tsk)
  {
  	unsigned long long clock;

  	clock = local_clock();

  	if (clock < tsk->vtime_snap)
  		return 0;

  	return clock - tsk->vtime_snap;
  }
  
  static cputime_t get_vtime_delta(struct task_struct *tsk)

  {

  	unsigned long long delta = vtime_delta(tsk);

  	WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_SLEEPING);
  	tsk->vtime_snap += delta;

  
  	/* CHECKME: always safe to convert nsecs to cputime? */
  	return nsecs_to_cputime(delta);
  }

  static void __vtime_account_system(struct task_struct *tsk)
  {
  	cputime_t delta_cpu = get_vtime_delta(tsk);
  
  	account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
  }

  void vtime_account_system(struct task_struct *tsk)
  {

  	if (!vtime_accounting_enabled())
  		return;
  
  	write_seqlock(&tsk->vtime_seqlock);
  	__vtime_account_system(tsk);
  	write_sequnlock(&tsk->vtime_seqlock);
  }

  void vtime_account_irq_exit(struct task_struct *tsk)
  {

  	if (!vtime_accounting_enabled())
  		return;

  	write_seqlock(&tsk->vtime_seqlock);
  	if (context_tracking_in_user())
  		tsk->vtime_snap_whence = VTIME_USER;
  	__vtime_account_system(tsk);
  	write_sequnlock(&tsk->vtime_seqlock);

  }
  
  void vtime_account_user(struct task_struct *tsk)
  {

  	cputime_t delta_cpu;
  
  	if (!vtime_accounting_enabled())
  		return;

  	delta_cpu = get_vtime_delta(tsk);

  	write_seqlock(&tsk->vtime_seqlock);
  	tsk->vtime_snap_whence = VTIME_SYS;

  	account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));

  	write_sequnlock(&tsk->vtime_seqlock);
  }
  
  void vtime_user_enter(struct task_struct *tsk)
  {
  	if (!vtime_accounting_enabled())
  		return;
  
  	write_seqlock(&tsk->vtime_seqlock);
  	tsk->vtime_snap_whence = VTIME_USER;
  	__vtime_account_system(tsk);
  	write_sequnlock(&tsk->vtime_seqlock);
  }
  
  void vtime_guest_enter(struct task_struct *tsk)
  {
  	write_seqlock(&tsk->vtime_seqlock);
  	__vtime_account_system(tsk);
  	current->flags |= PF_VCPU;
  	write_sequnlock(&tsk->vtime_seqlock);
  }
  
  void vtime_guest_exit(struct task_struct *tsk)
  {
  	write_seqlock(&tsk->vtime_seqlock);
  	__vtime_account_system(tsk);
  	current->flags &= ~PF_VCPU;
  	write_sequnlock(&tsk->vtime_seqlock);

  }
  
  void vtime_account_idle(struct task_struct *tsk)
  {

  	cputime_t delta_cpu = get_vtime_delta(tsk);

  
  	account_idle_time(delta_cpu);
  }

  
  bool vtime_accounting_enabled(void)
  {
  	return context_tracking_active();
  }

  
  void arch_vtime_task_switch(struct task_struct *prev)
  {
  	write_seqlock(&prev->vtime_seqlock);
  	prev->vtime_snap_whence = VTIME_SLEEPING;
  	write_sequnlock(&prev->vtime_seqlock);
  
  	write_seqlock(&current->vtime_seqlock);
  	current->vtime_snap_whence = VTIME_SYS;

  	current->vtime_snap = sched_clock_cpu(smp_processor_id());

  	write_sequnlock(&current->vtime_seqlock);
  }

  void vtime_init_idle(struct task_struct *t, int cpu)

  {
  	unsigned long flags;
  
  	write_seqlock_irqsave(&t->vtime_seqlock, flags);
  	t->vtime_snap_whence = VTIME_SYS;

  	t->vtime_snap = sched_clock_cpu(cpu);

  	write_sequnlock_irqrestore(&t->vtime_seqlock, flags);
  }
  
  cputime_t task_gtime(struct task_struct *t)
  {

  	unsigned int seq;
  	cputime_t gtime;
  
  	do {

  		seq = read_seqbegin(&t->vtime_seqlock);

  
  		gtime = t->gtime;
  		if (t->flags & PF_VCPU)
  			gtime += vtime_delta(t);

  	} while (read_seqretry(&t->vtime_seqlock, seq));

  
  	return gtime;
  }
  
  /*
   * Fetch cputime raw values from fields of task_struct and
   * add up the pending nohz execution time since the last
   * cputime snapshot.
   */
  static void
  fetch_task_cputime(struct task_struct *t,
  		   cputime_t *u_dst, cputime_t *s_dst,
  		   cputime_t *u_src, cputime_t *s_src,
  		   cputime_t *udelta, cputime_t *sdelta)
  {

  	unsigned int seq;
  	unsigned long long delta;
  
  	do {
  		*udelta = 0;
  		*sdelta = 0;

  		seq = read_seqbegin(&t->vtime_seqlock);

  
  		if (u_dst)
  			*u_dst = *u_src;
  		if (s_dst)
  			*s_dst = *s_src;
  
  		/* Task is sleeping, nothing to add */
  		if (t->vtime_snap_whence == VTIME_SLEEPING ||
  		    is_idle_task(t))
  			continue;
  
  		delta = vtime_delta(t);
  
  		/*
  		 * Task runs either in user or kernel space, add pending nohz time to
  		 * the right place.
  		 */
  		if (t->vtime_snap_whence == VTIME_USER || t->flags & PF_VCPU) {
  			*udelta = delta;
  		} else {
  			if (t->vtime_snap_whence == VTIME_SYS)
  				*sdelta = delta;
  		}

  	} while (read_seqretry(&t->vtime_seqlock, seq));

  }
  
  
  void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
  {
  	cputime_t udelta, sdelta;
  
  	fetch_task_cputime(t, utime, stime, &t->utime,
  			   &t->stime, &udelta, &sdelta);
  	if (utime)
  		*utime += udelta;
  	if (stime)
  		*stime += sdelta;
  }
  
  void task_cputime_scaled(struct task_struct *t,
  			 cputime_t *utimescaled, cputime_t *stimescaled)
  {
  	cputime_t udelta, sdelta;
  
  	fetch_task_cputime(t, utimescaled, stimescaled,
  			   &t->utimescaled, &t->stimescaled, &udelta, &sdelta);
  	if (utimescaled)
  		*utimescaled += cputime_to_scaled(udelta);
  	if (stimescaled)
  		*stimescaled += cputime_to_scaled(sdelta);
  }

  #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */