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vtime.c

/*
 *  arch/s390/kernel/vtime.c
 *    Virtual cpu timer based timer functions.
 *
 *  S390 version
 *    Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/types.h>
#include <linux/timex.h>
#include <linux/notifier.h>
#include <linux/kernel_stat.h>
#include <linux/rcupdate.h>
#include <linux/posix-timers.h>

#include <asm/s390_ext.h>
#include <asm/timer.h>
#include <asm/irq_regs.h>

static ext_int_info_t ext_int_info_timer;
static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);

#ifdef CONFIG_VIRT_CPU_ACCOUNTING
/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_process_tick(struct task_struct *tsk, int user_tick)
{
      cputime_t cputime;
      __u64 timer, clock;
      int rcu_user_flag;

      timer = S390_lowcore.last_update_timer;
      clock = S390_lowcore.last_update_clock;
      asm volatile ("  STPT %0\n"    /* Store current cpu timer value */
                  "  STCK %1"      /* Store current tod clock value */
                  : "=m" (S390_lowcore.last_update_timer),
                    "=m" (S390_lowcore.last_update_clock) );
      S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
      S390_lowcore.steal_clock += S390_lowcore.last_update_clock - clock;

      cputime = S390_lowcore.user_timer >> 12;
      rcu_user_flag = cputime != 0;
      S390_lowcore.user_timer -= cputime << 12;
      S390_lowcore.steal_clock -= cputime << 12;
      account_user_time(tsk, cputime);

      cputime =  S390_lowcore.system_timer >> 12;
      S390_lowcore.system_timer -= cputime << 12;
      S390_lowcore.steal_clock -= cputime << 12;
      account_system_time(tsk, HARDIRQ_OFFSET, cputime);

      cputime = S390_lowcore.steal_clock;
      if ((__s64) cputime > 0) {
            cputime >>= 12;
            S390_lowcore.steal_clock -= cputime << 12;
            account_steal_time(tsk, cputime);
      }
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_vtime(struct task_struct *tsk)
{
      cputime_t cputime;
      __u64 timer;

      timer = S390_lowcore.last_update_timer;
      asm volatile ("  STPT %0"    /* Store current cpu timer value */
                  : "=m" (S390_lowcore.last_update_timer) );
      S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

      cputime = S390_lowcore.user_timer >> 12;
      S390_lowcore.user_timer -= cputime << 12;
      S390_lowcore.steal_clock -= cputime << 12;
      account_user_time(tsk, cputime);

      cputime =  S390_lowcore.system_timer >> 12;
      S390_lowcore.system_timer -= cputime << 12;
      S390_lowcore.steal_clock -= cputime << 12;
      account_system_time(tsk, 0, cputime);
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void account_system_vtime(struct task_struct *tsk)
{
      cputime_t cputime;
      __u64 timer;

      timer = S390_lowcore.last_update_timer;
      asm volatile ("  STPT %0"    /* Store current cpu timer value */
                  : "=m" (S390_lowcore.last_update_timer) );
      S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

      cputime =  S390_lowcore.system_timer >> 12;
      S390_lowcore.system_timer -= cputime << 12;
      S390_lowcore.steal_clock -= cputime << 12;
      account_system_time(tsk, 0, cputime);
}
EXPORT_SYMBOL_GPL(account_system_vtime);

static inline void set_vtimer(__u64 expires)
{
      __u64 timer;

      asm volatile ("  STPT %0\n"  /* Store current cpu timer value */
                  "  SPT %1"     /* Set new value immediatly afterwards */
                  : "=m" (timer) : "m" (expires) );
      S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
      S390_lowcore.last_update_timer = expires;

      /* store expire time for this CPU timer */
      __get_cpu_var(virt_cpu_timer).to_expire = expires;
}
#else
static inline void set_vtimer(__u64 expires)
{
      S390_lowcore.last_update_timer = expires;
      asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));

      /* store expire time for this CPU timer */
      __get_cpu_var(virt_cpu_timer).to_expire = expires;
}
#endif

void vtime_start_cpu_timer(void)
{
      struct vtimer_queue *vt_list;

      vt_list = &__get_cpu_var(virt_cpu_timer);

      /* CPU timer interrupt is pending, don't reprogramm it */
      if (vt_list->idle & 1LL<<63)
            return;

      if (!list_empty(&vt_list->list))
            set_vtimer(vt_list->idle);
}

void vtime_stop_cpu_timer(void)
{
      struct vtimer_queue *vt_list;

      vt_list = &__get_cpu_var(virt_cpu_timer);

      /* nothing to do */
      if (list_empty(&vt_list->list)) {
            vt_list->idle = VTIMER_MAX_SLICE;
            goto fire;
      }

      /* store the actual expire value */
      asm volatile ("STPT %0" : "=m" (vt_list->idle));

      /*
       * If the CPU timer is negative we don't reprogramm
       * it because we will get instantly an interrupt.
       */
      if (vt_list->idle & 1LL<<63)
            return;

      vt_list->offset += vt_list->to_expire - vt_list->idle;

      /*
       * We cannot halt the CPU timer, we just write a value that
       * nearly never expires (only after 71 years) and re-write
       * the stored expire value if we continue the timer
       */
 fire:
      set_vtimer(VTIMER_MAX_SLICE);
}

/*
 * Sorted add to a list. List is linear searched until first bigger
 * element is found.
 */
static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
{
      struct vtimer_list *event;

      list_for_each_entry(event, head, entry) {
            if (event->expires > timer->expires) {
                  list_add_tail(&timer->entry, &event->entry);
                  return;
            }
      }
      list_add_tail(&timer->entry, head);
}

/*
 * Do the callback functions of expired vtimer events.
 * Called from within the interrupt handler.
 */
static void do_callbacks(struct list_head *cb_list)
{
      struct vtimer_queue *vt_list;
      struct vtimer_list *event, *tmp;
      void (*fn)(unsigned long);
      unsigned long data;

      if (list_empty(cb_list))
            return;

      vt_list = &__get_cpu_var(virt_cpu_timer);

      list_for_each_entry_safe(event, tmp, cb_list, entry) {
            fn = event->function;
            data = event->data;
            fn(data);

            if (!event->interval)
                  /* delete one shot timer */
                  list_del_init(&event->entry);
            else {
                  /* move interval timer back to list */
                  spin_lock(&vt_list->lock);
                  list_del_init(&event->entry);
                  list_add_sorted(event, &vt_list->list);
                  spin_unlock(&vt_list->lock);
            }
      }
}

/*
 * Handler for the virtual CPU timer.
 */
static void do_cpu_timer_interrupt(__u16 error_code)
{
      __u64 next, delta;
      struct vtimer_queue *vt_list;
      struct vtimer_list *event, *tmp;
      struct list_head *ptr;
      /* the callback queue */
      struct list_head cb_list;

      INIT_LIST_HEAD(&cb_list);
      vt_list = &__get_cpu_var(virt_cpu_timer);

      /* walk timer list, fire all expired events */
      spin_lock(&vt_list->lock);

      if (vt_list->to_expire < VTIMER_MAX_SLICE)
            vt_list->offset += vt_list->to_expire;

      list_for_each_entry_safe(event, tmp, &vt_list->list, entry) {
            if (event->expires > vt_list->offset)
                  /* found first unexpired event, leave */
                  break;

            /* re-charge interval timer, we have to add the offset */
            if (event->interval)
                  event->expires = event->interval + vt_list->offset;

            /* move expired timer to the callback queue */
            list_move_tail(&event->entry, &cb_list);
      }
      spin_unlock(&vt_list->lock);
      do_callbacks(&cb_list);

      /* next event is first in list */
      spin_lock(&vt_list->lock);
      if (!list_empty(&vt_list->list)) {
            ptr = vt_list->list.next;
            event = list_entry(ptr, struct vtimer_list, entry);
            next = event->expires - vt_list->offset;

            /* add the expired time from this interrupt handler
             * and the callback functions
             */
            asm volatile ("STPT %0" : "=m" (delta));
            delta = 0xffffffffffffffffLL - delta + 1;
            vt_list->offset += delta;
            next -= delta;
      } else {
            vt_list->offset = 0;
            next = VTIMER_MAX_SLICE;
      }
      spin_unlock(&vt_list->lock);
      set_vtimer(next);
}

void init_virt_timer(struct vtimer_list *timer)
{
      timer->function = NULL;
      INIT_LIST_HEAD(&timer->entry);
      spin_lock_init(&timer->lock);
}
EXPORT_SYMBOL(init_virt_timer);

static inline int vtimer_pending(struct vtimer_list *timer)
{
      return (!list_empty(&timer->entry));
}

/*
 * this function should only run on the specified CPU
 */
static void internal_add_vtimer(struct vtimer_list *timer)
{
      unsigned long flags;
      __u64 done;
      struct vtimer_list *event;
      struct vtimer_queue *vt_list;

      vt_list = &per_cpu(virt_cpu_timer, timer->cpu);
      spin_lock_irqsave(&vt_list->lock, flags);

      BUG_ON(timer->cpu != smp_processor_id());

      /* if list is empty we only have to set the timer */
      if (list_empty(&vt_list->list)) {
            /* reset the offset, this may happen if the last timer was
             * just deleted by mod_virt_timer and the interrupt
             * didn't happen until here
             */
            vt_list->offset = 0;
            goto fire;
      }

      /* save progress */
      asm volatile ("STPT %0" : "=m" (done));

      /* calculate completed work */
      done = vt_list->to_expire - done + vt_list->offset;
      vt_list->offset = 0;

      list_for_each_entry(event, &vt_list->list, entry)
            event->expires -= done;

 fire:
      list_add_sorted(timer, &vt_list->list);

      /* get first element, which is the next vtimer slice */
      event = list_entry(vt_list->list.next, struct vtimer_list, entry);

      set_vtimer(event->expires);
      spin_unlock_irqrestore(&vt_list->lock, flags);
      /* release CPU acquired in prepare_vtimer or mod_virt_timer() */
      put_cpu();
}

static inline void prepare_vtimer(struct vtimer_list *timer)
{
      BUG_ON(!timer->function);
      BUG_ON(!timer->expires || timer->expires > VTIMER_MAX_SLICE);
      BUG_ON(vtimer_pending(timer));
      timer->cpu = get_cpu();
}

/*
 * add_virt_timer - add an oneshot virtual CPU timer
 */
void add_virt_timer(void *new)
{
      struct vtimer_list *timer;

      timer = (struct vtimer_list *)new;
      prepare_vtimer(timer);
      timer->interval = 0;
      internal_add_vtimer(timer);
}
EXPORT_SYMBOL(add_virt_timer);

/*
 * add_virt_timer_int - add an interval virtual CPU timer
 */
void add_virt_timer_periodic(void *new)
{
      struct vtimer_list *timer;

      timer = (struct vtimer_list *)new;
      prepare_vtimer(timer);
      timer->interval = timer->expires;
      internal_add_vtimer(timer);
}
EXPORT_SYMBOL(add_virt_timer_periodic);

/*
 * If we change a pending timer the function must be called on the CPU
 * where the timer is running on, e.g. by smp_call_function_single()
 *
 * The original mod_timer adds the timer if it is not pending. For compatibility
 * we do the same. The timer will be added on the current CPU as a oneshot timer.
 *
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer(struct vtimer_list *timer, __u64 expires)
{
      struct vtimer_queue *vt_list;
      unsigned long flags;
      int cpu;

      BUG_ON(!timer->function);
      BUG_ON(!expires || expires > VTIMER_MAX_SLICE);

      /*
       * This is a common optimization triggered by the
       * networking code - if the timer is re-modified
       * to be the same thing then just return:
       */
      if (timer->expires == expires && vtimer_pending(timer))
            return 1;

      cpu = get_cpu();
      vt_list = &per_cpu(virt_cpu_timer, cpu);

      /* check if we run on the right CPU */
      BUG_ON(timer->cpu != cpu);

      /* disable interrupts before test if timer is pending */
      spin_lock_irqsave(&vt_list->lock, flags);

      /* if timer isn't pending add it on the current CPU */
      if (!vtimer_pending(timer)) {
            spin_unlock_irqrestore(&vt_list->lock, flags);
            /* we do not activate an interval timer with mod_virt_timer */
            timer->interval = 0;
            timer->expires = expires;
            timer->cpu = cpu;
            internal_add_vtimer(timer);
            return 0;
      }

      list_del_init(&timer->entry);
      timer->expires = expires;

      /* also change the interval if we have an interval timer */
      if (timer->interval)
            timer->interval = expires;

      /* the timer can't expire anymore so we can release the lock */
      spin_unlock_irqrestore(&vt_list->lock, flags);
      internal_add_vtimer(timer);
      return 1;
}
EXPORT_SYMBOL(mod_virt_timer);

/*
 * delete a virtual timer
 *
 * returns whether the deleted timer was pending (1) or not (0)
 */
int del_virt_timer(struct vtimer_list *timer)
{
      unsigned long flags;
      struct vtimer_queue *vt_list;

      /* check if timer is pending */
      if (!vtimer_pending(timer))
            return 0;

      vt_list = &per_cpu(virt_cpu_timer, timer->cpu);
      spin_lock_irqsave(&vt_list->lock, flags);

      /* we don't interrupt a running timer, just let it expire! */
      list_del_init(&timer->entry);

      /* last timer removed */
      if (list_empty(&vt_list->list)) {
            vt_list->to_expire = 0;
            vt_list->offset = 0;
      }

      spin_unlock_irqrestore(&vt_list->lock, flags);
      return 1;
}
EXPORT_SYMBOL(del_virt_timer);

/*
 * Start the virtual CPU timer on the current CPU.
 */
void init_cpu_vtimer(void)
{
      struct vtimer_queue *vt_list;

      /* kick the virtual timer */
      S390_lowcore.exit_timer = VTIMER_MAX_SLICE;
      S390_lowcore.last_update_timer = VTIMER_MAX_SLICE;
      asm volatile ("SPT %0" : : "m" (S390_lowcore.last_update_timer));
      asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));

      /* enable cpu timer interrupts */
      __ctl_set_bit(0,10);

      vt_list = &__get_cpu_var(virt_cpu_timer);
      INIT_LIST_HEAD(&vt_list->list);
      spin_lock_init(&vt_list->lock);
      vt_list->to_expire = 0;
      vt_list->offset = 0;
      vt_list->idle = 0;

}

void __init vtime_init(void)
{
      /* request the cpu timer external interrupt */
      if (register_early_external_interrupt(0x1005, do_cpu_timer_interrupt,
                                    &ext_int_info_timer) != 0)
            panic("Couldn't request external interrupt 0x1005");

      /* Enable cpu timer interrupts on the boot cpu. */
      init_cpu_vtimer();
}


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