/*
   *  linux/kernel/timer.c
   *

   *  Kernel internal timers, basic process system calls

   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  1997-01-28  Modified by Finn Arne Gangstad to make timers scale better.
   *
   *  1997-09-10  Updated NTP code according to technical memorandum Jan '96
   *              "A Kernel Model for Precision Timekeeping" by Dave Mills
   *  1998-12-24  Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
   *              serialize accesses to xtime/lost_ticks).
   *                              Copyright (C) 1998  Andrea Arcangeli
   *  1999-03-10  Improved NTP compatibility by Ulrich Windl
   *  2002-05-31	Move sys_sysinfo here and make its locking sane, Robert Love
   *  2000-10-05  Implemented scalable SMP per-CPU timer handling.
   *                              Copyright (C) 2000, 2001, 2002  Ingo Molnar
   *              Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
   */
  
  #include <linux/kernel_stat.h>

  #include <linux/export.h>

  #include <linux/interrupt.h>
  #include <linux/percpu.h>
  #include <linux/init.h>
  #include <linux/mm.h>
  #include <linux/swap.h>

  #include <linux/pid_namespace.h>

  #include <linux/notifier.h>
  #include <linux/thread_info.h>
  #include <linux/time.h>
  #include <linux/jiffies.h>
  #include <linux/posix-timers.h>
  #include <linux/cpu.h>
  #include <linux/syscalls.h>

  #include <linux/delay.h>

  #include <linux/tick.h>

  #include <linux/kallsyms.h>

  #include <linux/irq_work.h>

  #include <linux/sched.h>

  #include <linux/slab.h>

  
  #include <asm/uaccess.h>
  #include <asm/unistd.h>
  #include <asm/div64.h>
  #include <asm/timex.h>
  #include <asm/io.h>

  #define CREATE_TRACE_POINTS
  #include <trace/events/timer.h>

  u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
  
  EXPORT_SYMBOL(jiffies_64);

  /*
   * per-CPU timer vector definitions:
   */

  #define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
  #define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
  #define TVN_SIZE (1 << TVN_BITS)
  #define TVR_SIZE (1 << TVR_BITS)
  #define TVN_MASK (TVN_SIZE - 1)
  #define TVR_MASK (TVR_SIZE - 1)

  struct tvec {

  	struct list_head vec[TVN_SIZE];

  };

  struct tvec_root {

  	struct list_head vec[TVR_SIZE];

  };

  struct tvec_base {

  	spinlock_t lock;
  	struct timer_list *running_timer;

  	unsigned long timer_jiffies;

  	unsigned long next_timer;

  	struct tvec_root tv1;
  	struct tvec tv2;
  	struct tvec tv3;
  	struct tvec tv4;
  	struct tvec tv5;

  } ____cacheline_aligned;

  struct tvec_base boot_tvec_bases;

  EXPORT_SYMBOL(boot_tvec_bases);

  static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;

  /* Functions below help us manage 'deferrable' flag */

  static inline unsigned int tbase_get_deferrable(struct tvec_base *base)

  {

  	return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);

  }

  static inline struct tvec_base *tbase_get_base(struct tvec_base *base)

  {

  	return ((struct tvec_base *)((unsigned long)base & ~TBASE_DEFERRABLE_FLAG));

  }
  
  static inline void timer_set_deferrable(struct timer_list *timer)
  {

  	timer->base = TBASE_MAKE_DEFERRED(timer->base);

  }
  
  static inline void

  timer_set_base(struct timer_list *timer, struct tvec_base *new_base)

  {

  	timer->base = (struct tvec_base *)((unsigned long)(new_base) |

  				      tbase_get_deferrable(timer->base));

  }

  static unsigned long round_jiffies_common(unsigned long j, int cpu,
  		bool force_up)

  {
  	int rem;
  	unsigned long original = j;
  
  	/*
  	 * We don't want all cpus firing their timers at once hitting the
  	 * same lock or cachelines, so we skew each extra cpu with an extra
  	 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
  	 * already did this.
  	 * The skew is done by adding 3*cpunr, then round, then subtract this
  	 * extra offset again.
  	 */
  	j += cpu * 3;
  
  	rem = j % HZ;
  
  	/*
  	 * If the target jiffie is just after a whole second (which can happen
  	 * due to delays of the timer irq, long irq off times etc etc) then
  	 * we should round down to the whole second, not up. Use 1/4th second
  	 * as cutoff for this rounding as an extreme upper bound for this.

  	 * But never round down if @force_up is set.

  	 */

  	if (rem < HZ/4 && !force_up) /* round down */

  		j = j - rem;
  	else /* round up */
  		j = j - rem + HZ;
  
  	/* now that we have rounded, subtract the extra skew again */
  	j -= cpu * 3;
  
  	if (j <= jiffies) /* rounding ate our timeout entirely; */
  		return original;
  	return j;
  }

  
  /**
   * __round_jiffies - function to round jiffies to a full second
   * @j: the time in (absolute) jiffies that should be rounded
   * @cpu: the processor number on which the timeout will happen
   *
   * __round_jiffies() rounds an absolute time in the future (in jiffies)
   * up or down to (approximately) full seconds. This is useful for timers
   * for which the exact time they fire does not matter too much, as long as
   * they fire approximately every X seconds.
   *
   * By rounding these timers to whole seconds, all such timers will fire
   * at the same time, rather than at various times spread out. The goal
   * of this is to have the CPU wake up less, which saves power.
   *
   * The exact rounding is skewed for each processor to avoid all
   * processors firing at the exact same time, which could lead
   * to lock contention or spurious cache line bouncing.
   *
   * The return value is the rounded version of the @j parameter.
   */
  unsigned long __round_jiffies(unsigned long j, int cpu)
  {
  	return round_jiffies_common(j, cpu, false);
  }

  EXPORT_SYMBOL_GPL(__round_jiffies);
  
  /**
   * __round_jiffies_relative - function to round jiffies to a full second
   * @j: the time in (relative) jiffies that should be rounded
   * @cpu: the processor number on which the timeout will happen
   *

   * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)

   * up or down to (approximately) full seconds. This is useful for timers
   * for which the exact time they fire does not matter too much, as long as
   * they fire approximately every X seconds.
   *
   * By rounding these timers to whole seconds, all such timers will fire
   * at the same time, rather than at various times spread out. The goal
   * of this is to have the CPU wake up less, which saves power.
   *
   * The exact rounding is skewed for each processor to avoid all
   * processors firing at the exact same time, which could lead
   * to lock contention or spurious cache line bouncing.
   *

   * The return value is the rounded version of the @j parameter.

   */
  unsigned long __round_jiffies_relative(unsigned long j, int cpu)
  {

  	unsigned long j0 = jiffies;
  
  	/* Use j0 because jiffies might change while we run */
  	return round_jiffies_common(j + j0, cpu, false) - j0;

  }
  EXPORT_SYMBOL_GPL(__round_jiffies_relative);
  
  /**
   * round_jiffies - function to round jiffies to a full second
   * @j: the time in (absolute) jiffies that should be rounded
   *

   * round_jiffies() rounds an absolute time in the future (in jiffies)

   * up or down to (approximately) full seconds. This is useful for timers
   * for which the exact time they fire does not matter too much, as long as
   * they fire approximately every X seconds.
   *
   * By rounding these timers to whole seconds, all such timers will fire
   * at the same time, rather than at various times spread out. The goal
   * of this is to have the CPU wake up less, which saves power.
   *

   * The return value is the rounded version of the @j parameter.

   */
  unsigned long round_jiffies(unsigned long j)
  {

  	return round_jiffies_common(j, raw_smp_processor_id(), false);

  }
  EXPORT_SYMBOL_GPL(round_jiffies);
  
  /**
   * round_jiffies_relative - function to round jiffies to a full second
   * @j: the time in (relative) jiffies that should be rounded
   *

   * round_jiffies_relative() rounds a time delta  in the future (in jiffies)

   * up or down to (approximately) full seconds. This is useful for timers
   * for which the exact time they fire does not matter too much, as long as
   * they fire approximately every X seconds.
   *
   * By rounding these timers to whole seconds, all such timers will fire
   * at the same time, rather than at various times spread out. The goal
   * of this is to have the CPU wake up less, which saves power.
   *

   * The return value is the rounded version of the @j parameter.

   */
  unsigned long round_jiffies_relative(unsigned long j)
  {
  	return __round_jiffies_relative(j, raw_smp_processor_id());
  }
  EXPORT_SYMBOL_GPL(round_jiffies_relative);

  /**
   * __round_jiffies_up - function to round jiffies up to a full second
   * @j: the time in (absolute) jiffies that should be rounded
   * @cpu: the processor number on which the timeout will happen
   *
   * This is the same as __round_jiffies() except that it will never
   * round down.  This is useful for timeouts for which the exact time
   * of firing does not matter too much, as long as they don't fire too
   * early.
   */
  unsigned long __round_jiffies_up(unsigned long j, int cpu)
  {
  	return round_jiffies_common(j, cpu, true);
  }
  EXPORT_SYMBOL_GPL(__round_jiffies_up);
  
  /**
   * __round_jiffies_up_relative - function to round jiffies up to a full second
   * @j: the time in (relative) jiffies that should be rounded
   * @cpu: the processor number on which the timeout will happen
   *
   * This is the same as __round_jiffies_relative() except that it will never
   * round down.  This is useful for timeouts for which the exact time
   * of firing does not matter too much, as long as they don't fire too
   * early.
   */
  unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
  {
  	unsigned long j0 = jiffies;
  
  	/* Use j0 because jiffies might change while we run */
  	return round_jiffies_common(j + j0, cpu, true) - j0;
  }
  EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
  
  /**
   * round_jiffies_up - function to round jiffies up to a full second
   * @j: the time in (absolute) jiffies that should be rounded
   *
   * This is the same as round_jiffies() except that it will never
   * round down.  This is useful for timeouts for which the exact time
   * of firing does not matter too much, as long as they don't fire too
   * early.
   */
  unsigned long round_jiffies_up(unsigned long j)
  {
  	return round_jiffies_common(j, raw_smp_processor_id(), true);
  }
  EXPORT_SYMBOL_GPL(round_jiffies_up);
  
  /**
   * round_jiffies_up_relative - function to round jiffies up to a full second
   * @j: the time in (relative) jiffies that should be rounded
   *
   * This is the same as round_jiffies_relative() except that it will never
   * round down.  This is useful for timeouts for which the exact time
   * of firing does not matter too much, as long as they don't fire too
   * early.
   */
  unsigned long round_jiffies_up_relative(unsigned long j)
  {
  	return __round_jiffies_up_relative(j, raw_smp_processor_id());
  }
  EXPORT_SYMBOL_GPL(round_jiffies_up_relative);

  /**
   * set_timer_slack - set the allowed slack for a timer

   * @timer: the timer to be modified

   * @slack_hz: the amount of time (in jiffies) allowed for rounding
   *
   * Set the amount of time, in jiffies, that a certain timer has
   * in terms of slack. By setting this value, the timer subsystem
   * will schedule the actual timer somewhere between
   * the time mod_timer() asks for, and that time plus the slack.
   *
   * By setting the slack to -1, a percentage of the delay is used
   * instead.
   */
  void set_timer_slack(struct timer_list *timer, int slack_hz)
  {
  	timer->slack = slack_hz;
  }
  EXPORT_SYMBOL_GPL(set_timer_slack);

  static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)

  {
  	unsigned long expires = timer->expires;
  	unsigned long idx = expires - base->timer_jiffies;
  	struct list_head *vec;
  
  	if (idx < TVR_SIZE) {
  		int i = expires & TVR_MASK;
  		vec = base->tv1.vec + i;
  	} else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
  		int i = (expires >> TVR_BITS) & TVN_MASK;
  		vec = base->tv2.vec + i;
  	} else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
  		int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
  		vec = base->tv3.vec + i;
  	} else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
  		int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
  		vec = base->tv4.vec + i;
  	} else if ((signed long) idx < 0) {
  		/*
  		 * Can happen if you add a timer with expires == jiffies,
  		 * or you set a timer to go off in the past
  		 */
  		vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
  	} else {
  		int i;
  		/* If the timeout is larger than 0xffffffff on 64-bit
  		 * architectures then we use the maximum timeout:
  		 */
  		if (idx > 0xffffffffUL) {
  			idx = 0xffffffffUL;
  			expires = idx + base->timer_jiffies;
  		}
  		i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
  		vec = base->tv5.vec + i;
  	}
  	/*
  	 * Timers are FIFO:
  	 */
  	list_add_tail(&timer->entry, vec);
  }

  #ifdef CONFIG_TIMER_STATS
  void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
  {
  	if (timer->start_site)
  		return;
  
  	timer->start_site = addr;
  	memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
  	timer->start_pid = current->pid;
  }

  
  static void timer_stats_account_timer(struct timer_list *timer)
  {
  	unsigned int flag = 0;

  	if (likely(!timer->start_site))
  		return;

  	if (unlikely(tbase_get_deferrable(timer->base)))
  		flag |= TIMER_STATS_FLAG_DEFERRABLE;
  
  	timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
  				 timer->function, timer->start_comm, flag);
  }
  
  #else
  static void timer_stats_account_timer(struct timer_list *timer) {}

  #endif

  #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
  
  static struct debug_obj_descr timer_debug_descr;

  static void *timer_debug_hint(void *addr)
  {
  	return ((struct timer_list *) addr)->function;
  }

  /*
   * fixup_init is called when:
   * - an active object is initialized

   */

  static int timer_fixup_init(void *addr, enum debug_obj_state state)
  {
  	struct timer_list *timer = addr;
  
  	switch (state) {
  	case ODEBUG_STATE_ACTIVE:
  		del_timer_sync(timer);
  		debug_object_init(timer, &timer_debug_descr);
  		return 1;
  	default:
  		return 0;
  	}
  }
  
  /*
   * fixup_activate is called when:
   * - an active object is activated
   * - an unknown object is activated (might be a statically initialized object)
   */
  static int timer_fixup_activate(void *addr, enum debug_obj_state state)
  {
  	struct timer_list *timer = addr;
  
  	switch (state) {
  
  	case ODEBUG_STATE_NOTAVAILABLE:
  		/*
  		 * This is not really a fixup. The timer was
  		 * statically initialized. We just make sure that it
  		 * is tracked in the object tracker.
  		 */
  		if (timer->entry.next == NULL &&
  		    timer->entry.prev == TIMER_ENTRY_STATIC) {
  			debug_object_init(timer, &timer_debug_descr);
  			debug_object_activate(timer, &timer_debug_descr);
  			return 0;
  		} else {
  			WARN_ON_ONCE(1);
  		}
  		return 0;
  
  	case ODEBUG_STATE_ACTIVE:
  		WARN_ON(1);
  
  	default:
  		return 0;
  	}
  }
  
  /*
   * fixup_free is called when:
   * - an active object is freed
   */
  static int timer_fixup_free(void *addr, enum debug_obj_state state)
  {
  	struct timer_list *timer = addr;
  
  	switch (state) {
  	case ODEBUG_STATE_ACTIVE:
  		del_timer_sync(timer);
  		debug_object_free(timer, &timer_debug_descr);
  		return 1;
  	default:
  		return 0;
  	}
  }
  
  static struct debug_obj_descr timer_debug_descr = {
  	.name		= "timer_list",

  	.debug_hint	= timer_debug_hint,

  	.fixup_init	= timer_fixup_init,
  	.fixup_activate	= timer_fixup_activate,
  	.fixup_free	= timer_fixup_free,
  };
  
  static inline void debug_timer_init(struct timer_list *timer)
  {
  	debug_object_init(timer, &timer_debug_descr);
  }
  
  static inline void debug_timer_activate(struct timer_list *timer)
  {
  	debug_object_activate(timer, &timer_debug_descr);
  }
  
  static inline void debug_timer_deactivate(struct timer_list *timer)
  {
  	debug_object_deactivate(timer, &timer_debug_descr);
  }
  
  static inline void debug_timer_free(struct timer_list *timer)
  {
  	debug_object_free(timer, &timer_debug_descr);
  }

  static void __init_timer(struct timer_list *timer,
  			 const char *name,
  			 struct lock_class_key *key);

  void init_timer_on_stack_key(struct timer_list *timer,
  			     const char *name,
  			     struct lock_class_key *key)

  {
  	debug_object_init_on_stack(timer, &timer_debug_descr);

  	__init_timer(timer, name, key);

  }

  EXPORT_SYMBOL_GPL(init_timer_on_stack_key);

  
  void destroy_timer_on_stack(struct timer_list *timer)
  {
  	debug_object_free(timer, &timer_debug_descr);
  }
  EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
  
  #else
  static inline void debug_timer_init(struct timer_list *timer) { }
  static inline void debug_timer_activate(struct timer_list *timer) { }
  static inline void debug_timer_deactivate(struct timer_list *timer) { }
  #endif

  static inline void debug_init(struct timer_list *timer)
  {
  	debug_timer_init(timer);
  	trace_timer_init(timer);
  }
  
  static inline void
  debug_activate(struct timer_list *timer, unsigned long expires)
  {
  	debug_timer_activate(timer);
  	trace_timer_start(timer, expires);
  }
  
  static inline void debug_deactivate(struct timer_list *timer)
  {
  	debug_timer_deactivate(timer);
  	trace_timer_cancel(timer);
  }

  static void __init_timer(struct timer_list *timer,
  			 const char *name,
  			 struct lock_class_key *key)

  {
  	timer->entry.next = NULL;

  	timer->base = __raw_get_cpu_var(tvec_bases);

  	timer->slack = -1;

  #ifdef CONFIG_TIMER_STATS
  	timer->start_site = NULL;
  	timer->start_pid = -1;
  	memset(timer->start_comm, 0, TASK_COMM_LEN);
  #endif

  	lockdep_init_map(&timer->lockdep_map, name, key, 0);

  }

  void setup_deferrable_timer_on_stack_key(struct timer_list *timer,
  					 const char *name,
  					 struct lock_class_key *key,
  					 void (*function)(unsigned long),
  					 unsigned long data)
  {
  	timer->function = function;
  	timer->data = data;
  	init_timer_on_stack_key(timer, name, key);
  	timer_set_deferrable(timer);
  }
  EXPORT_SYMBOL_GPL(setup_deferrable_timer_on_stack_key);

  /**

   * init_timer_key - initialize a timer

   * @timer: the timer to be initialized

   * @name: name of the timer
   * @key: lockdep class key of the fake lock used for tracking timer
   *       sync lock dependencies

   *

   * init_timer_key() must be done to a timer prior calling *any* of the

   * other timer functions.
   */

  void init_timer_key(struct timer_list *timer,
  		    const char *name,
  		    struct lock_class_key *key)

  {

  	debug_init(timer);

  	__init_timer(timer, name, key);

  }

  EXPORT_SYMBOL(init_timer_key);

  void init_timer_deferrable_key(struct timer_list *timer,
  			       const char *name,
  			       struct lock_class_key *key)

  {

  	init_timer_key(timer, name, key);

  	timer_set_deferrable(timer);
  }

  EXPORT_SYMBOL(init_timer_deferrable_key);

  static inline void detach_timer(struct timer_list *timer,

  				int clear_pending)

  {
  	struct list_head *entry = &timer->entry;

  	debug_deactivate(timer);

  	__list_del(entry->prev, entry->next);
  	if (clear_pending)
  		entry->next = NULL;
  	entry->prev = LIST_POISON2;
  }
  
  /*

   * We are using hashed locking: holding per_cpu(tvec_bases).lock

   * means that all timers which are tied to this base via timer->base are
   * locked, and the base itself is locked too.
   *
   * So __run_timers/migrate_timers can safely modify all timers which could
   * be found on ->tvX lists.
   *
   * When the timer's base is locked, and the timer removed from list, it is
   * possible to set timer->base = NULL and drop the lock: the timer remains
   * locked.
   */

  static struct tvec_base *lock_timer_base(struct timer_list *timer,

  					unsigned long *flags)

  	__acquires(timer->base->lock)

  {

  	struct tvec_base *base;

  
  	for (;;) {

  		struct tvec_base *prelock_base = timer->base;

  		base = tbase_get_base(prelock_base);

  		if (likely(base != NULL)) {
  			spin_lock_irqsave(&base->lock, *flags);

  			if (likely(prelock_base == timer->base))

  				return base;
  			/* The timer has migrated to another CPU */
  			spin_unlock_irqrestore(&base->lock, *flags);
  		}
  		cpu_relax();
  	}
  }

  static inline int

  __mod_timer(struct timer_list *timer, unsigned long expires,
  						bool pending_only, int pinned)

  {

  	struct tvec_base *base, *new_base;

  	unsigned long flags;

  	int ret = 0 , cpu;

  	timer_stats_timer_set_start_info(timer);

  	BUG_ON(!timer->function);

  	base = lock_timer_base(timer, &flags);
  
  	if (timer_pending(timer)) {
  		detach_timer(timer, 0);

  		if (timer->expires == base->next_timer &&
  		    !tbase_get_deferrable(timer->base))
  			base->next_timer = base->timer_jiffies;

  		ret = 1;

  	} else {
  		if (pending_only)
  			goto out_unlock;

  	}

  	debug_activate(timer, expires);

  	cpu = smp_processor_id();
  
  #if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)

  	if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
  		cpu = get_nohz_timer_target();

  #endif
  	new_base = per_cpu(tvec_bases, cpu);

  	if (base != new_base) {

  		/*

  		 * We are trying to schedule the timer on the local CPU.
  		 * However we can't change timer's base while it is running,
  		 * otherwise del_timer_sync() can't detect that the timer's
  		 * handler yet has not finished. This also guarantees that
  		 * the timer is serialized wrt itself.

  		 */

  		if (likely(base->running_timer != timer)) {

  			/* See the comment in lock_timer_base() */

  			timer_set_base(timer, NULL);

  			spin_unlock(&base->lock);

  			base = new_base;
  			spin_lock(&base->lock);

  			timer_set_base(timer, base);

  		}
  	}

  	timer->expires = expires;

  	if (time_before(timer->expires, base->next_timer) &&
  	    !tbase_get_deferrable(timer->base))
  		base->next_timer = timer->expires;

  	internal_add_timer(base, timer);

  
  out_unlock:

  	spin_unlock_irqrestore(&base->lock, flags);

  
  	return ret;
  }

  /**

   * mod_timer_pending - modify a pending timer's timeout
   * @timer: the pending timer to be modified
   * @expires: new timeout in jiffies

   *

   * mod_timer_pending() is the same for pending timers as mod_timer(),
   * but will not re-activate and modify already deleted timers.
   *
   * It is useful for unserialized use of timers.

   */

  int mod_timer_pending(struct timer_list *timer, unsigned long expires)

  {

  	return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);

  }

  EXPORT_SYMBOL(mod_timer_pending);

  /*
   * Decide where to put the timer while taking the slack into account
   *
   * Algorithm:
   *   1) calculate the maximum (absolute) time
   *   2) calculate the highest bit where the expires and new max are different
   *   3) use this bit to make a mask
   *   4) use the bitmask to round down the maximum time, so that all last
   *      bits are zeros
   */
  static inline
  unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
  {
  	unsigned long expires_limit, mask;
  	int bit;

  	if (timer->slack >= 0) {

  		expires_limit = expires + timer->slack;

  	} else {

  		long delta = expires - jiffies;
  
  		if (delta < 256)
  			return expires;

  		expires_limit = expires + delta / 256;

  	}

  	mask = expires ^ expires_limit;

  	if (mask == 0)
  		return expires;
  
  	bit = find_last_bit(&mask, BITS_PER_LONG);
  
  	mask = (1 << bit) - 1;
  
  	expires_limit = expires_limit & ~(mask);
  
  	return expires_limit;
  }

  /**

   * mod_timer - modify a timer's timeout
   * @timer: the timer to be modified

   * @expires: new timeout in jiffies

   *

   * mod_timer() is a more efficient way to update the expire field of an

   * active timer (if the timer is inactive it will be activated)
   *
   * mod_timer(timer, expires) is equivalent to:
   *
   *     del_timer(timer); timer->expires = expires; add_timer(timer);
   *
   * Note that if there are multiple unserialized concurrent users of the
   * same timer, then mod_timer() is the only safe way to modify the timeout,
   * since add_timer() cannot modify an already running timer.
   *
   * The function returns whether it has modified a pending timer or not.
   * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
   * active timer returns 1.)
   */
  int mod_timer(struct timer_list *timer, unsigned long expires)
  {

  	expires = apply_slack(timer, expires);

  	/*
  	 * 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_pending(timer) && timer->expires == expires)

  		return 1;

  	return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);

  }

  EXPORT_SYMBOL(mod_timer);

  /**

   * mod_timer_pinned - modify a timer's timeout
   * @timer: the timer to be modified
   * @expires: new timeout in jiffies
   *
   * mod_timer_pinned() is a way to update the expire field of an
   * active timer (if the timer is inactive it will be activated)
   * and not allow the timer to be migrated to a different CPU.
   *
   * mod_timer_pinned(timer, expires) is equivalent to:
   *
   *     del_timer(timer); timer->expires = expires; add_timer(timer);
   */
  int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
  {
  	if (timer->expires == expires && timer_pending(timer))
  		return 1;
  
  	return __mod_timer(timer, expires, false, TIMER_PINNED);
  }
  EXPORT_SYMBOL(mod_timer_pinned);
  
  /**

   * add_timer - start a timer
   * @timer: the timer to be added
   *
   * The kernel will do a ->function(->data) callback from the
   * timer interrupt at the ->expires point in the future. The
   * current time is 'jiffies'.
   *
   * The timer's ->expires, ->function (and if the handler uses it, ->data)
   * fields must be set prior calling this function.
   *
   * Timers with an ->expires field in the past will be executed in the next
   * timer tick.
   */
  void add_timer(struct timer_list *timer)
  {
  	BUG_ON(timer_pending(timer));
  	mod_timer(timer, timer->expires);
  }
  EXPORT_SYMBOL(add_timer);
  
  /**
   * add_timer_on - start a timer on a particular CPU
   * @timer: the timer to be added
   * @cpu: the CPU to start it on
   *
   * This is not very scalable on SMP. Double adds are not possible.
   */
  void add_timer_on(struct timer_list *timer, int cpu)
  {
  	struct tvec_base *base = per_cpu(tvec_bases, cpu);
  	unsigned long flags;
  
  	timer_stats_timer_set_start_info(timer);
  	BUG_ON(timer_pending(timer) || !timer->function);
  	spin_lock_irqsave(&base->lock, flags);
  	timer_set_base(timer, base);

  	debug_activate(timer, timer->expires);

  	if (time_before(timer->expires, base->next_timer) &&
  	    !tbase_get_deferrable(timer->base))
  		base->next_timer = timer->expires;

  	internal_add_timer(base, timer);
  	/*
  	 * Check whether the other CPU is idle and needs to be
  	 * triggered to reevaluate the timer wheel when nohz is
  	 * active. We are protected against the other CPU fiddling
  	 * with the timer by holding the timer base lock. This also
  	 * makes sure that a CPU on the way to idle can not evaluate
  	 * the timer wheel.
  	 */
  	wake_up_idle_cpu(cpu);
  	spin_unlock_irqrestore(&base->lock, flags);
  }

  EXPORT_SYMBOL_GPL(add_timer_on);

  
  /**

   * del_timer - deactive a timer.
   * @timer: the timer to be deactivated
   *
   * del_timer() deactivates a timer - this works on both active and inactive
   * timers.
   *
   * The function returns whether it has deactivated a pending timer or not.
   * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
   * active timer returns 1.)
   */
  int del_timer(struct timer_list *timer)
  {

  	struct tvec_base *base;

  	unsigned long flags;

  	int ret = 0;

  	timer_stats_timer_clear_start_info(timer);

  	if (timer_pending(timer)) {
  		base = lock_timer_base(timer, &flags);
  		if (timer_pending(timer)) {
  			detach_timer(timer, 1);

  			if (timer->expires == base->next_timer &&
  			    !tbase_get_deferrable(timer->base))
  				base->next_timer = base->timer_jiffies;

  			ret = 1;
  		}

  		spin_unlock_irqrestore(&base->lock, flags);

  	}

  	return ret;

  }

  EXPORT_SYMBOL(del_timer);

  /**
   * try_to_del_timer_sync - Try to deactivate a timer
   * @timer: timer do del
   *

   * This function tries to deactivate a timer. Upon successful (ret >= 0)
   * exit the timer is not queued and the handler is not running on any CPU.

   */
  int try_to_del_timer_sync(struct timer_list *timer)
  {

  	struct tvec_base *base;

  	unsigned long flags;
  	int ret = -1;
  
  	base = lock_timer_base(timer, &flags);
  
  	if (base->running_timer == timer)
  		goto out;

  	timer_stats_timer_clear_start_info(timer);

  	ret = 0;
  	if (timer_pending(timer)) {
  		detach_timer(timer, 1);

  		if (timer->expires == base->next_timer &&
  		    !tbase_get_deferrable(timer->base))
  			base->next_timer = base->timer_jiffies;

  		ret = 1;
  	}
  out:
  	spin_unlock_irqrestore(&base->lock, flags);
  
  	return ret;
  }

  EXPORT_SYMBOL(try_to_del_timer_sync);

  #ifdef CONFIG_SMP

  /**

   * del_timer_sync - deactivate a timer and wait for the handler to finish.
   * @timer: the timer to be deactivated
   *
   * This function only differs from del_timer() on SMP: besides deactivating
   * the timer it also makes sure the handler has finished executing on other
   * CPUs.
   *

   * Synchronization rules: Callers must prevent restarting of the timer,

   * otherwise this function is meaningless. It must not be called from

   * interrupt contexts. The caller must not hold locks which would prevent

   * completion of the timer's handler. The timer's handler must not call
   * add_timer_on(). Upon exit the timer is not queued and the handler is
   * not running on any CPU.

   *

   * Note: You must not hold locks that are held in interrupt context
   *   while calling this function. Even if the lock has nothing to do
   *   with the timer in question.  Here's why:
   *
   *    CPU0                             CPU1
   *    ----                             ----
   *                                   <SOFTIRQ>
   *                                   call_timer_fn();
   *                                     base->running_timer = mytimer;
   *  spin_lock_irq(somelock);
   *                                     <IRQ>
   *                                        spin_lock(somelock);
   *  del_timer_sync(mytimer);
   *   while (base->running_timer == mytimer);
   *
   * Now del_timer_sync() will never return and never release somelock.
   * The interrupt on the other CPU is waiting to grab somelock but
   * it has interrupted the softirq that CPU0 is waiting to finish.
   *

   * The function returns whether it has deactivated a pending timer or not.

   */
  int del_timer_sync(struct timer_list *timer)
  {

  #ifdef CONFIG_LOCKDEP

  	unsigned long flags;

  	/*
  	 * If lockdep gives a backtrace here, please reference
  	 * the synchronization rules above.
  	 */

  	local_irq_save(flags);

  	lock_map_acquire(&timer->lockdep_map);
  	lock_map_release(&timer->lockdep_map);

  	local_irq_restore(flags);

  #endif

  	/*
  	 * don't use it in hardirq context, because it
  	 * could lead to deadlock.
  	 */
  	WARN_ON(in_irq());

  	for (;;) {
  		int ret = try_to_del_timer_sync(timer);
  		if (ret >= 0)
  			return ret;

  		cpu_relax();

  	}

  }

  EXPORT_SYMBOL(del_timer_sync);

  #endif

  static int cascade(struct tvec_base *base, struct tvec *tv, int index)

  {
  	/* cascade all the timers from tv up one level */

  	struct timer_list *timer, *tmp;
  	struct list_head tv_list;
  
  	list_replace_init(tv->vec + index, &tv_list);

  	/*

  	 * We are removing _all_ timers from the list, so we
  	 * don't have to detach them individually.

  	 */

  	list_for_each_entry_safe(timer, tmp, &tv_list, entry) {

  		BUG_ON(tbase_get_base(timer->base) != base);

  		internal_add_timer(base, timer);

  	}

  
  	return index;
  }

  static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
  			  unsigned long data)
  {
  	int preempt_count = preempt_count();
  
  #ifdef CONFIG_LOCKDEP
  	/*
  	 * It is permissible to free the timer from inside the
  	 * function that is called from it, this we need to take into
  	 * account for lockdep too. To avoid bogus "held lock freed"
  	 * warnings as well as problems when looking into
  	 * timer->lockdep_map, make a copy and use that here.
  	 */
  	struct lockdep_map lockdep_map = timer->lockdep_map;
  #endif
  	/*
  	 * Couple the lock chain with the lock chain at
  	 * del_timer_sync() by acquiring the lock_map around the fn()
  	 * call here and in del_timer_sync().
  	 */
  	lock_map_acquire(&lockdep_map);
  
  	trace_timer_expire_entry(timer);
  	fn(data);
  	trace_timer_expire_exit(timer);
  
  	lock_map_release(&lockdep_map);
  
  	if (preempt_count != preempt_count()) {

  		WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x
  ",
  			  fn, preempt_count, preempt_count());
  		/*
  		 * Restore the preempt count. That gives us a decent
  		 * chance to survive and extract information. If the
  		 * callback kept a lock held, bad luck, but not worse
  		 * than the BUG() we had.
  		 */
  		preempt_count() = preempt_count;

  	}
  }

  #define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
  
  /**

   * __run_timers - run all expired timers (if any) on this CPU.
   * @base: the timer vector to be processed.
   *
   * This function cascades all vectors and executes all expired timer
   * vectors.
   */

  static inline void __run_timers(struct tvec_base *base)

  {
  	struct timer_list *timer;

  	spin_lock_irq(&base->lock);

  	while (time_after_eq(jiffies, base->timer_jiffies)) {

  		struct list_head work_list;

  		struct list_head *head = &work_list;

  		int index = base->timer_jiffies & TVR_MASK;

  		/*
  		 * Cascade timers:
  		 */
  		if (!index &&
  			(!cascade(base, &base->tv2, INDEX(0))) &&
  				(!cascade(base, &base->tv3, INDEX(1))) &&
  					!cascade(base, &base->tv4, INDEX(2)))
  			cascade(base, &base->tv5, INDEX(3));

  		++base->timer_jiffies;
  		list_replace_init(base->tv1.vec + index, &work_list);

  		while (!list_empty(head)) {

  			void (*fn)(unsigned long);
  			unsigned long data;

  			timer = list_first_entry(head, struct timer_list,entry);

  			fn = timer->function;
  			data = timer->data;

  			timer_stats_account_timer(timer);

  			base->running_timer = timer;

  			detach_timer(timer, 1);

  			spin_unlock_irq(&base->lock);

  			call_timer_fn(timer, fn, data);

  			spin_lock_irq(&base->lock);

  		}
  	}

  	base->running_timer = NULL;

  	spin_unlock_irq(&base->lock);

  }

  #ifdef CONFIG_NO_HZ

  /*
   * Find out when the next timer event is due to happen. This

   * is used on S/390 to stop all activity when a CPU is idle.
   * This function needs to be called with interrupts disabled.

   */

  static unsigned long __next_timer_interrupt(struct tvec_base *base)

  {

  	unsigned long timer_jiffies = base->timer_jiffies;

  	unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;

  	int index, slot, array, found = 0;

  	struct timer_list *nte;

  	struct tvec *varray[4];

  
  	/* Look for timer events in tv1. */

  	index = slot = timer_jiffies & TVR_MASK;

  	do {

  		list_for_each_entry(nte, base->tv1.vec + slot, entry) {

  			if (tbase_get_deferrable(nte->base))
  				continue;

  			found = 1;

  			expires = nte->expires;

  			/* Look at the cascade bucket(s)? */
  			if (!index || slot < index)
  				goto cascade;
  			return expires;

  		}

  		slot = (slot + 1) & TVR_MASK;
  	} while (slot != index);
  
  cascade:
  	/* Calculate the next cascade event */
  	if (index)
  		timer_jiffies += TVR_SIZE - index;
  	timer_jiffies >>= TVR_BITS;

  
  	/* Check tv2-tv5. */
  	varray[0] = &base->tv2;
  	varray[1] = &base->tv3;
  	varray[2] = &base->tv4;
  	varray[3] = &base->tv5;

  
  	for (array = 0; array < 4; array++) {

  		struct tvec *varp = varray[array];

  
  		index = slot = timer_jiffies & TVN_MASK;

  		do {

  			list_for_each_entry(nte, varp->vec + slot, entry) {

  				if (tbase_get_deferrable(nte->base))
  					continue;

  				found = 1;

  				if (time_before(nte->expires, expires))
  					expires = nte->expires;

  			}
  			/*
  			 * Do we still search for the first timer or are
  			 * we looking up the cascade buckets ?
  			 */
  			if (found) {
  				/* Look at the cascade bucket(s)? */
  				if (!index || slot < index)
  					break;
  				return expires;
  			}
  			slot = (slot + 1) & TVN_MASK;
  		} while (slot != index);
  
  		if (index)
  			timer_jiffies += TVN_SIZE - index;
  		timer_jiffies >>= TVN_BITS;

  	}

  	return expires;
  }

  /*
   * Check, if the next hrtimer event is before the next timer wheel
   * event:
   */
  static unsigned long cmp_next_hrtimer_event(unsigned long now,
  					    unsigned long expires)
  {
  	ktime_t hr_delta = hrtimer_get_next_event();
  	struct timespec tsdelta;

  	unsigned long delta;

  
  	if (hr_delta.tv64 == KTIME_MAX)
  		return expires;

  	/*
  	 * Expired timer available, let it expire in the next tick
  	 */
  	if (hr_delta.tv64 <= 0)
  		return now + 1;

  	tsdelta = ktime_to_timespec(hr_delta);

  	delta = timespec_to_jiffies(&tsdelta);

  
  	/*
  	 * Limit the delta to the max value, which is checked in
  	 * tick_nohz_stop_sched_tick():
  	 */
  	if (delta > NEXT_TIMER_MAX_DELTA)
  		delta = NEXT_TIMER_MAX_DELTA;

  	/*
  	 * Take rounding errors in to account and make sure, that it
  	 * expires in the next tick. Otherwise we go into an endless
  	 * ping pong due to tick_nohz_stop_sched_tick() retriggering
  	 * the timer softirq
  	 */
  	if (delta < 1)
  		delta = 1;
  	now += delta;

  	if (time_before(now, expires))
  		return now;

  	return expires;
  }

  
  /**

   * get_next_timer_interrupt - return the jiffy of the next pending timer

   * @now: current time (in jiffies)

   */

  unsigned long get_next_timer_interrupt(unsigned long now)

  {

  	struct tvec_base *base = __this_cpu_read(tvec_bases);

  	unsigned long expires;

  	/*
  	 * Pretend that there is no timer pending if the cpu is offline.
  	 * Possible pending timers will be migrated later to an active cpu.
  	 */
  	if (cpu_is_offline(smp_processor_id()))
  		return now + NEXT_TIMER_MAX_DELTA;

  	spin_lock(&base->lock);

  	if (time_before_eq(base->next_timer, base->timer_jiffies))
  		base->next_timer = __next_timer_interrupt(base);
  	expires = base->next_timer;

  	spin_unlock(&base->lock);
  
  	if (time_before_eq(expires, now))
  		return now;
  
  	return cmp_next_hrtimer_event(now, expires);
  }

  #endif

  /*

   * Called from the timer interrupt handler to charge one tick to the current

   * process.  user_tick is 1 if the tick is user time, 0 for system.
   */
  void update_process_times(int user_tick)
  {
  	struct task_struct *p = current;
  	int cpu = smp_processor_id();
  
  	/* Note: this timer irq context must be accounted for as well. */

  	account_process_tick(p, user_tick);

  	run_local_timers();

  	rcu_check_callbacks(cpu, user_tick);

  	printk_tick();

  #ifdef CONFIG_IRQ_WORK
  	if (in_irq())
  		irq_work_run();
  #endif

  	scheduler_tick();

  	run_posix_cpu_timers(p);

  }
  
  /*

   * This function runs timers and the timer-tq in bottom half context.
   */
  static void run_timer_softirq(struct softirq_action *h)
  {

  	struct tvec_base *base = __this_cpu_read(tvec_bases);

  	hrtimer_run_pending();

  	if (time_after_eq(jiffies, base->timer_jiffies))
  		__run_timers(base);
  }
  
  /*
   * Called by the local, per-CPU timer interrupt on SMP.
   */
  void run_local_timers(void)
  {

  	hrtimer_run_queues();

  	raise_softirq(TIMER_SOFTIRQ);
  }

  #ifdef __ARCH_WANT_SYS_ALARM
  
  /*
   * For backwards compatibility?  This can be done in libc so Alpha
   * and all newer ports shouldn't need it.
   */

  SYSCALL_DEFINE1(alarm, unsigned int, seconds)

  {

  	return alarm_setitimer(seconds);

  }
  
  #endif
  
  #ifndef __alpha__
  
  /*
   * The Alpha uses getxpid, getxuid, and getxgid instead.  Maybe this
   * should be moved into arch/i386 instead?
   */
  
  /**
   * sys_getpid - return the thread group id of the current process
   *
   * Note, despite the name, this returns the tgid not the pid.  The tgid and
   * the pid are identical unless CLONE_THREAD was specified on clone() in
   * which case the tgid is the same in all threads of the same group.
   *
   * This is SMP safe as current->tgid does not change.
   */

  SYSCALL_DEFINE0(getpid)

  {

  	return task_tgid_vnr(current);

  }
  
  /*

   * Accessing ->real_parent is not SMP-safe, it could
   * change from under us. However, we can use a stale
   * value of ->real_parent under rcu_read_lock(), see
   * release_task()->call_rcu(delayed_put_task_struct).

   */

  SYSCALL_DEFINE0(getppid)

  {
  	int pid;

  	rcu_read_lock();

  	pid = task_tgid_vnr(current->real_parent);

  	rcu_read_unlock();

  	return pid;
  }

  SYSCALL_DEFINE0(getuid)

  {
  	/* Only we change this so SMP safe */

  	return current_uid();

  }

  SYSCALL_DEFINE0(geteuid)

  {
  	/* Only we change this so SMP safe */

  	return current_euid();

  }

  SYSCALL_DEFINE0(getgid)

  {
  	/* Only we change this so SMP safe */

  	return current_gid();

  }

  SYSCALL_DEFINE0(getegid)

  {
  	/* Only we change this so SMP safe */

  	return  current_egid();

  }
  
  #endif
  
  static void process_timeout(unsigned long __data)
  {

  	wake_up_process((struct task_struct *)__data);

  }
  
  /**
   * schedule_timeout - sleep until timeout
   * @timeout: timeout value in jiffies
   *
   * Make the current task sleep until @timeout jiffies have
   * elapsed. The routine will return immediately unless
   * the current task state has been set (see set_current_state()).
   *
   * You can set the task state as follows -
   *
   * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
   * pass before the routine returns. The routine will return 0
   *
   * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
   * delivered to the current task. In this case the remaining time
   * in jiffies will be returned, or 0 if the timer expired in time
   *
   * The current task state is guaranteed to be TASK_RUNNING when this
   * routine returns.
   *
   * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
   * the CPU away without a bound on the timeout. In this case the return
   * value will be %MAX_SCHEDULE_TIMEOUT.
   *
   * In all cases the return value is guaranteed to be non-negative.
   */

  signed long __sched schedule_timeout(signed long timeout)

  {
  	struct timer_list timer;
  	unsigned long expire;
  
  	switch (timeout)
  	{
  	case MAX_SCHEDULE_TIMEOUT:
  		/*
  		 * These two special cases are useful to be comfortable
  		 * in the caller. Nothing more. We could take
  		 * MAX_SCHEDULE_TIMEOUT from one of the negative value
  		 * but I' d like to return a valid offset (>=0) to allow
  		 * the caller to do everything it want with the retval.
  		 */
  		schedule();
  		goto out;
  	default:
  		/*
  		 * Another bit of PARANOID. Note that the retval will be
  		 * 0 since no piece of kernel is supposed to do a check
  		 * for a negative retval of schedule_timeout() (since it
  		 * should never happens anyway). You just have the printk()
  		 * that will tell you if something is gone wrong and where.
  		 */

  		if (timeout < 0) {

  			printk(KERN_ERR "schedule_timeout: wrong timeout "

  				"value %lx
  ", timeout);
  			dump_stack();

  			current->state = TASK_RUNNING;
  			goto out;
  		}
  	}
  
  	expire = timeout + jiffies;

  	setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);

  	__mod_timer(&timer, expire, false, TIMER_NOT_PINNED);

  	schedule();
  	del_singleshot_timer_sync(&timer);

  	/* Remove the timer from the object tracker */
  	destroy_timer_on_stack(&timer);

  	timeout = expire - jiffies;
  
   out:
  	return timeout < 0 ? 0 : timeout;
  }

  EXPORT_SYMBOL(schedule_timeout);

  /*
   * We can use __set_current_state() here because schedule_timeout() calls
   * schedule() unconditionally.
   */

  signed long __sched schedule_timeout_interruptible(signed long timeout)
  {

  	__set_current_state(TASK_INTERRUPTIBLE);
  	return schedule_timeout(timeout);

  }
  EXPORT_SYMBOL(schedule_timeout_interruptible);

  signed long __sched schedule_timeout_killable(signed long timeout)
  {
  	__set_current_state(TASK_KILLABLE);
  	return schedule_timeout(timeout);
  }
  EXPORT_SYMBOL(schedule_timeout_killable);

  signed long __sched schedule_timeout_uninterruptible(signed long timeout)
  {

  	__set_current_state(TASK_UNINTERRUPTIBLE);
  	return schedule_timeout(timeout);

  }
  EXPORT_SYMBOL(schedule_timeout_uninterruptible);

  /* Thread ID - the internal kernel "pid" */

  SYSCALL_DEFINE0(gettid)

  {

  	return task_pid_vnr(current);

  }

  /**

   * do_sysinfo - fill in sysinfo struct

   * @info: pointer to buffer to fill

   */

  int do_sysinfo(struct sysinfo *info)

  {

  	unsigned long mem_total, sav_total;
  	unsigned int mem_unit, bitcount;

  	struct timespec tp;

  	memset(info, 0, sizeof(struct sysinfo));

  	ktime_get_ts(&tp);
  	monotonic_to_bootbased(&tp);
  	info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);

  	get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT);

  	info->procs = nr_threads;

  	si_meminfo(info);
  	si_swapinfo(info);

  
  	/*
  	 * If the sum of all the available memory (i.e. ram + swap)
  	 * is less than can be stored in a 32 bit unsigned long then
  	 * we can be binary compatible with 2.2.x kernels.  If not,
  	 * well, in that case 2.2.x was broken anyways...
  	 *
  	 *  -Erik Andersen <andersee@debian.org>
  	 */

  	mem_total = info->totalram + info->totalswap;
  	if (mem_total < info->totalram || mem_total < info->totalswap)

  		goto out;
  	bitcount = 0;

  	mem_unit = info->mem_unit;

  	while (mem_unit > 1) {
  		bitcount++;
  		mem_unit >>= 1;
  		sav_total = mem_total;
  		mem_total <<= 1;
  		if (mem_total < sav_total)
  			goto out;
  	}
  
  	/*
  	 * If mem_total did not overflow, multiply all memory values by

  	 * info->mem_unit and set it to 1.  This leaves things compatible

  	 * with 2.2.x, and also retains compatibility with earlier 2.4.x
  	 * kernels...
  	 */

  	info->mem_unit = 1;
  	info->totalram <<= bitcount;
  	info->freeram <<= bitcount;
  	info->sharedram <<= bitcount;
  	info->bufferram <<= bitcount;
  	info->totalswap <<= bitcount;
  	info->freeswap <<= bitcount;
  	info->totalhigh <<= bitcount;
  	info->freehigh <<= bitcount;
  
  out:
  	return 0;
  }

  SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info)

  {
  	struct sysinfo val;
  
  	do_sysinfo(&val);

  	if (copy_to_user(info, &val, sizeof(struct sysinfo)))
  		return -EFAULT;
  
  	return 0;
  }

  static int __cpuinit init_timers_cpu(int cpu)

  {
  	int j;

  	struct tvec_base *base;

  	static char __cpuinitdata tvec_base_done[NR_CPUS];

  	if (!tvec_base_done[cpu]) {

  		static char boot_done;

  		if (boot_done) {

  			/*
  			 * The APs use this path later in boot
  			 */

  			base = kmalloc_node(sizeof(*base),
  						GFP_KERNEL | __GFP_ZERO,

  						cpu_to_node(cpu));
  			if (!base)
  				return -ENOMEM;

  
  			/* Make sure that tvec_base is 2 byte aligned */
  			if (tbase_get_deferrable(base)) {
  				WARN_ON(1);
  				kfree(base);
  				return -ENOMEM;
  			}

  			per_cpu(tvec_bases, cpu) = base;

  		} else {

  			/*
  			 * This is for the boot CPU - we use compile-time
  			 * static initialisation because per-cpu memory isn't
  			 * ready yet and because the memory allocators are not
  			 * initialised either.
  			 */

  			boot_done = 1;

  			base = &boot_tvec_bases;

  		}

  		tvec_base_done[cpu] = 1;
  	} else {
  		base = per_cpu(tvec_bases, cpu);

  	}

  	spin_lock_init(&base->lock);

  	for (j = 0; j < TVN_SIZE; j++) {
  		INIT_LIST_HEAD(base->tv5.vec + j);
  		INIT_LIST_HEAD(base->tv4.vec + j);
  		INIT_LIST_HEAD(base->tv3.vec + j);
  		INIT_LIST_HEAD(base->tv2.vec + j);
  	}
  	for (j = 0; j < TVR_SIZE; j++)
  		INIT_LIST_HEAD(base->tv1.vec + j);
  
  	base->timer_jiffies = jiffies;

  	base->next_timer = base->timer_jiffies;

  	return 0;

  }
  
  #ifdef CONFIG_HOTPLUG_CPU

  static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)

  {
  	struct timer_list *timer;
  
  	while (!list_empty(head)) {

  		timer = list_first_entry(head, struct timer_list, entry);

  		detach_timer(timer, 0);

  		timer_set_base(timer, new_base);

  		if (time_before(timer->expires, new_base->next_timer) &&
  		    !tbase_get_deferrable(timer->base))
  			new_base->next_timer = timer->expires;

  		internal_add_timer(new_base, timer);

  	}

  }

  static void __cpuinit migrate_timers(int cpu)

  {

  	struct tvec_base *old_base;
  	struct tvec_base *new_base;

  	int i;
  
  	BUG_ON(cpu_online(cpu));

  	old_base = per_cpu(tvec_bases, cpu);
  	new_base = get_cpu_var(tvec_bases);

  	/*
  	 * The caller is globally serialized and nobody else
  	 * takes two locks at once, deadlock is not possible.
  	 */
  	spin_lock_irq(&new_base->lock);

  	spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

  
  	BUG_ON(old_base->running_timer);

  	for (i = 0; i < TVR_SIZE; i++)

  		migrate_timer_list(new_base, old_base->tv1.vec + i);
  	for (i = 0; i < TVN_SIZE; i++) {
  		migrate_timer_list(new_base, old_base->tv2.vec + i);
  		migrate_timer_list(new_base, old_base->tv3.vec + i);
  		migrate_timer_list(new_base, old_base->tv4.vec + i);
  		migrate_timer_list(new_base, old_base->tv5.vec + i);
  	}

  	spin_unlock(&old_base->lock);

  	spin_unlock_irq(&new_base->lock);

  	put_cpu_var(tvec_bases);

  }
  #endif /* CONFIG_HOTPLUG_CPU */

  static int __cpuinit timer_cpu_notify(struct notifier_block *self,

  				unsigned long action, void *hcpu)
  {
  	long cpu = (long)hcpu;

  	int err;

  	switch(action) {
  	case CPU_UP_PREPARE:

  	case CPU_UP_PREPARE_FROZEN:

  		err = init_timers_cpu(cpu);
  		if (err < 0)
  			return notifier_from_errno(err);

  		break;
  #ifdef CONFIG_HOTPLUG_CPU
  	case CPU_DEAD:

  	case CPU_DEAD_FROZEN:

  		migrate_timers(cpu);
  		break;
  #endif
  	default:
  		break;
  	}
  	return NOTIFY_OK;
  }

  static struct notifier_block __cpuinitdata timers_nb = {

  	.notifier_call	= timer_cpu_notify,
  };
  
  
  void __init init_timers(void)
  {

  	int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,

  				(void *)(long)smp_processor_id());

  	init_timer_stats();

  	BUG_ON(err != NOTIFY_OK);

  	register_cpu_notifier(&timers_nb);

  	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);

  }

  /**
   * msleep - sleep safely even with waitqueue interruptions
   * @msecs: Time in milliseconds to sleep for
   */
  void msleep(unsigned int msecs)
  {
  	unsigned long timeout = msecs_to_jiffies(msecs) + 1;

  	while (timeout)
  		timeout = schedule_timeout_uninterruptible(timeout);

  }
  
  EXPORT_SYMBOL(msleep);
  
  /**

   * msleep_interruptible - sleep waiting for signals

   * @msecs: Time in milliseconds to sleep for
   */
  unsigned long msleep_interruptible(unsigned int msecs)
  {
  	unsigned long timeout = msecs_to_jiffies(msecs) + 1;

  	while (timeout && !signal_pending(current))
  		timeout = schedule_timeout_interruptible(timeout);

  	return jiffies_to_msecs(timeout);
  }
  
  EXPORT_SYMBOL(msleep_interruptible);

  
  static int __sched do_usleep_range(unsigned long min, unsigned long max)
  {
  	ktime_t kmin;
  	unsigned long delta;
  
  	kmin = ktime_set(0, min * NSEC_PER_USEC);
  	delta = (max - min) * NSEC_PER_USEC;
  	return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
  }
  
  /**
   * usleep_range - Drop in replacement for udelay where wakeup is flexible
   * @min: Minimum time in usecs to sleep
   * @max: Maximum time in usecs to sleep
   */
  void usleep_range(unsigned long min, unsigned long max)
  {
  	__set_current_state(TASK_UNINTERRUPTIBLE);
  	do_usleep_range(min, max);
  }
  EXPORT_SYMBOL(usleep_range);