arch/s390/kernel/vtime.c - arm/linux-arm64-legacy - Git at Google

 /*
  *    Virtual cpu timer based timer functions.
  *
  *    Copyright IBM Corp. 2004, 2012
  *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
  */

 #include <linux/kernel_stat.h>
 #include <linux/notifier.h>
 #include <linux/kprobes.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/timex.h>
 #include <linux/types.h>
 #include <linux/time.h>
 #include <linux/cpu.h>
 #include <linux/smp.h>

 #include <asm/irq_regs.h>
 #include <asm/cputime.h>
 #include <asm/vtimer.h>
 #include <asm/irq.h>
 #include "entry.h"

 static void virt_timer_expire(void);

 DEFINE_PER_CPU(struct s390_idle_data, s390_idle);

 static LIST_HEAD(virt_timer_list);
 static DEFINE_SPINLOCK(virt_timer_lock);
 static atomic64_t virt_timer_current;
 static atomic64_t virt_timer_elapsed;

 static inline u64 get_vtimer(void)
 {
 	u64 timer;

 	asm volatile("stpt %0" : "=m" (timer));
 	return timer;
 }

 static inline void set_vtimer(u64 expires)
 {
 	u64 timer;

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

 static inline int virt_timer_forward(u64 elapsed)
 {
 	BUG_ON(!irqs_disabled());

 	if (list_empty(&virt_timer_list))
 		return 0;
 	elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
 	return elapsed >= atomic64_read(&virt_timer_current);
 }

 /*
  * Update process times based on virtual cpu times stored by entry.S
  * to the lowcore fields user_timer, system_timer & steal_clock.
  */
 static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
 {
 	struct thread_info *ti = task_thread_info(tsk);
 	u64 timer, clock, user, system, steal;

 	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_timer += S390_lowcore.last_update_clock - clock;

 	user = S390_lowcore.user_timer - ti->user_timer;
 	S390_lowcore.steal_timer -= user;
 	ti->user_timer = S390_lowcore.user_timer;
 	account_user_time(tsk, user, user);

 	system = S390_lowcore.system_timer - ti->system_timer;
 	S390_lowcore.steal_timer -= system;
 	ti->system_timer = S390_lowcore.system_timer;
 	account_system_time(tsk, hardirq_offset, system, system);

 	steal = S390_lowcore.steal_timer;
 	if ((s64) steal > 0) {
 		S390_lowcore.steal_timer = 0;
 		account_steal_time(steal);
 	}

 	return virt_timer_forward(user + system);
 }

 void account_vtime(struct task_struct *prev, struct task_struct *next)
 {
 	struct thread_info *ti;

 	do_account_vtime(prev, 0);
 	ti = task_thread_info(prev);
 	ti->user_timer = S390_lowcore.user_timer;
 	ti->system_timer = S390_lowcore.system_timer;
 	ti = task_thread_info(next);
 	S390_lowcore.user_timer = ti->user_timer;
 	S390_lowcore.system_timer = ti->system_timer;
 }

 void account_process_tick(struct task_struct *tsk, int user_tick)
 {
 	if (do_account_vtime(tsk, HARDIRQ_OFFSET))
 		virt_timer_expire();
 }

 /*
  * 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)
 {
 	struct thread_info *ti = task_thread_info(tsk);
 	u64 timer, system;

 	timer = S390_lowcore.last_update_timer;
 	S390_lowcore.last_update_timer = get_vtimer();
 	S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

 	system = S390_lowcore.system_timer - ti->system_timer;
 	S390_lowcore.steal_timer -= system;
 	ti->system_timer = S390_lowcore.system_timer;
 	account_system_time(tsk, 0, system, system);

 	virt_timer_forward(system);
 }
 EXPORT_SYMBOL_GPL(account_system_vtime);

 void __kprobes vtime_stop_cpu(void)
 {
 	struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
 	unsigned long long idle_time;
 	unsigned long psw_mask;

 	trace_hardirqs_on();
 	/* Don't trace preempt off for idle. */
 	stop_critical_timings();

 	/* Wait for external, I/O or machine check interrupt. */
 	psw_mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_DAT |
 		PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
 	idle->nohz_delay = 0;

 	/* Call the assembler magic in entry.S */
 	psw_idle(idle, psw_mask);

 	/* Reenable preemption tracer. */
 	start_critical_timings();

 	/* Account time spent with enabled wait psw loaded as idle time. */
 	idle->sequence++;
 	smp_wmb();
 	idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
 	idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
 	idle->idle_time += idle_time;
 	idle->idle_count++;
 	account_idle_time(idle_time);
 	smp_wmb();
 	idle->sequence++;
 }

 cputime64_t s390_get_idle_time(int cpu)
 {
 	struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
 	unsigned long long now, idle_enter, idle_exit;
 	unsigned int sequence;

 	do {
 		now = get_clock();
 		sequence = ACCESS_ONCE(idle->sequence);
 		idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
 		idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
 	} while ((sequence & 1) || (idle->sequence != sequence));
 	return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
 }

 /*
  * 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 *tmp;

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

 /*
  * Handler for expired virtual CPU timer.
  */
 static void virt_timer_expire(void)
 {
 	struct vtimer_list *timer, *tmp;
 	unsigned long elapsed;
 	LIST_HEAD(cb_list);

 	/* walk timer list, fire all expired timers */
 	spin_lock(&virt_timer_lock);
 	elapsed = atomic64_read(&virt_timer_elapsed);
 	list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
 		if (timer->expires < elapsed)
 			/* move expired timer to the callback queue */
 			list_move_tail(&timer->entry, &cb_list);
 		else
 			timer->expires -= elapsed;
 	}
 	if (!list_empty(&virt_timer_list)) {
 		timer = list_first_entry(&virt_timer_list,
 					 struct vtimer_list, entry);
 		atomic64_set(&virt_timer_current, timer->expires);
 	}
 	atomic64_sub(elapsed, &virt_timer_elapsed);
 	spin_unlock(&virt_timer_lock);

 	/* Do callbacks and recharge periodic timers */
 	list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
 		list_del_init(&timer->entry);
 		timer->function(timer->data);
 		if (timer->interval) {
 			/* Recharge interval timer */
 			timer->expires = timer->interval +
 				atomic64_read(&virt_timer_elapsed);
 			spin_lock(&virt_timer_lock);
 			list_add_sorted(timer, &virt_timer_list);
 			spin_unlock(&virt_timer_lock);
 		}
 	}
 }

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

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

 static void internal_add_vtimer(struct vtimer_list *timer)
 {
 	if (list_empty(&virt_timer_list)) {
 		/* First timer, just program it. */
 		atomic64_set(&virt_timer_current, timer->expires);
 		atomic64_set(&virt_timer_elapsed, 0);
 		list_add(&timer->entry, &virt_timer_list);
 	} else {
 		/* Update timer against current base. */
 		timer->expires += atomic64_read(&virt_timer_elapsed);
 		if (likely((s64) timer->expires <
 			   (s64) atomic64_read(&virt_timer_current)))
 			/* The new timer expires before the current timer. */
 			atomic64_set(&virt_timer_current, timer->expires);
 		/* Insert new timer into the list. */
 		list_add_sorted(timer, &virt_timer_list);
 	}
 }

 static void __add_vtimer(struct vtimer_list *timer, int periodic)
 {
 	unsigned long flags;

 	timer->interval = periodic ? timer->expires : 0;
 	spin_lock_irqsave(&virt_timer_lock, flags);
 	internal_add_vtimer(timer);
 	spin_unlock_irqrestore(&virt_timer_lock, flags);
 }

 /*
  * add_virt_timer - add an oneshot virtual CPU timer
  */
 void add_virt_timer(struct vtimer_list *timer)
 {
 	__add_vtimer(timer, 0);
 }
 EXPORT_SYMBOL(add_virt_timer);

 /*
  * add_virt_timer_int - add an interval virtual CPU timer
  */
 void add_virt_timer_periodic(struct vtimer_list *timer)
 {
 	__add_vtimer(timer, 1);
 }
 EXPORT_SYMBOL(add_virt_timer_periodic);

 static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
 {
 	unsigned long flags;
 	int rc;

 	BUG_ON(!timer->function);

 	if (timer->expires == expires && vtimer_pending(timer))
 		return 1;
 	spin_lock_irqsave(&virt_timer_lock, flags);
 	rc = vtimer_pending(timer);
 	if (rc)
 		list_del_init(&timer->entry);
 	timer->interval = periodic ? expires : 0;
 	timer->expires = expires;
 	internal_add_vtimer(timer);
 	spin_unlock_irqrestore(&virt_timer_lock, flags);
 	return rc;
 }

 /*
  * returns whether it has modified a pending timer (1) or not (0)
  */
 int mod_virt_timer(struct vtimer_list *timer, u64 expires)
 {
 	return __mod_vtimer(timer, expires, 0);
 }
 EXPORT_SYMBOL(mod_virt_timer);

 /*
  * returns whether it has modified a pending timer (1) or not (0)
  */
 int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
 {
 	return __mod_vtimer(timer, expires, 1);
 }
 EXPORT_SYMBOL(mod_virt_timer_periodic);

 /*
  * 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;

 	if (!vtimer_pending(timer))
 		return 0;
 	spin_lock_irqsave(&virt_timer_lock, flags);
 	list_del_init(&timer->entry);
 	spin_unlock_irqrestore(&virt_timer_lock, flags);
 	return 1;
 }
 EXPORT_SYMBOL(del_virt_timer);

 /*
  * Start the virtual CPU timer on the current CPU.
  */
 void __cpuinit init_cpu_vtimer(void)
 {
 	/* set initial cpu timer */
 	set_vtimer(VTIMER_MAX_SLICE);
 }

 static int __cpuinit s390_nohz_notify(struct notifier_block *self,
 				      unsigned long action, void *hcpu)
 {
 	struct s390_idle_data *idle;
 	long cpu = (long) hcpu;

 	idle = &per_cpu(s390_idle, cpu);
 	switch (action) {
 	case CPU_DYING:
 	case CPU_DYING_FROZEN:
 		idle->nohz_delay = 0;
 	default:
 		break;
 	}
 	return NOTIFY_OK;
 }

 void __init vtime_init(void)
 {
 	/* Enable cpu timer interrupts on the boot cpu. */
 	init_cpu_vtimer();
 	cpu_notifier(s390_nohz_notify, 0);
 }
	/*
	* Virtual cpu timer based timer functions.
	*
	* Copyright IBM Corp. 2004, 2012
	* Author(s): Jan Glauber <jan.glauber@de.ibm.com>
	*/

	#include <linux/kernel_stat.h>
	#include <linux/notifier.h>
	#include <linux/kprobes.h>
	#include <linux/export.h>
	#include <linux/kernel.h>
	#include <linux/timex.h>
	#include <linux/types.h>
	#include <linux/time.h>
	#include <linux/cpu.h>
	#include <linux/smp.h>

	#include <asm/irq_regs.h>
	#include <asm/cputime.h>
	#include <asm/vtimer.h>
	#include <asm/irq.h>
	#include "entry.h"

	static void virt_timer_expire(void);

	DEFINE_PER_CPU(struct s390_idle_data, s390_idle);

	static LIST_HEAD(virt_timer_list);
	static DEFINE_SPINLOCK(virt_timer_lock);
	static atomic64_t virt_timer_current;
	static atomic64_t virt_timer_elapsed;

	static inline u64 get_vtimer(void)
	{
	u64 timer;

	asm volatile("stpt %0" : "=m" (timer));
	return timer;
	}

	static inline void set_vtimer(u64 expires)
	{
	u64 timer;

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

	static inline int virt_timer_forward(u64 elapsed)
	{
	BUG_ON(!irqs_disabled());

	if (list_empty(&virt_timer_list))
	return 0;
	elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
	return elapsed >= atomic64_read(&virt_timer_current);
	}

	/*
	* Update process times based on virtual cpu times stored by entry.S
	* to the lowcore fields user_timer, system_timer & steal_clock.
	*/
	static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
	{
	struct thread_info *ti = task_thread_info(tsk);
	u64 timer, clock, user, system, steal;

	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_timer += S390_lowcore.last_update_clock - clock;

	user = S390_lowcore.user_timer - ti->user_timer;
	S390_lowcore.steal_timer -= user;
	ti->user_timer = S390_lowcore.user_timer;
	account_user_time(tsk, user, user);

	system = S390_lowcore.system_timer - ti->system_timer;
	S390_lowcore.steal_timer -= system;
	ti->system_timer = S390_lowcore.system_timer;
	account_system_time(tsk, hardirq_offset, system, system);

	steal = S390_lowcore.steal_timer;
	if ((s64) steal > 0) {
	S390_lowcore.steal_timer = 0;
	account_steal_time(steal);
	}

	return virt_timer_forward(user + system);
	}

	void account_vtime(struct task_struct prev, struct task_struct next)
	{
	struct thread_info *ti;

	do_account_vtime(prev, 0);
	ti = task_thread_info(prev);
	ti->user_timer = S390_lowcore.user_timer;
	ti->system_timer = S390_lowcore.system_timer;
	ti = task_thread_info(next);
	S390_lowcore.user_timer = ti->user_timer;
	S390_lowcore.system_timer = ti->system_timer;
	}

	void account_process_tick(struct task_struct *tsk, int user_tick)
	{
	if (do_account_vtime(tsk, HARDIRQ_OFFSET))
	virt_timer_expire();
	}

	/*
	* 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)
	{
	struct thread_info *ti = task_thread_info(tsk);
	u64 timer, system;

	timer = S390_lowcore.last_update_timer;
	S390_lowcore.last_update_timer = get_vtimer();
	S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

	system = S390_lowcore.system_timer - ti->system_timer;
	S390_lowcore.steal_timer -= system;
	ti->system_timer = S390_lowcore.system_timer;
	account_system_time(tsk, 0, system, system);

	virt_timer_forward(system);
	}
	EXPORT_SYMBOL_GPL(account_system_vtime);

	void __kprobes vtime_stop_cpu(void)
	{
	struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
	unsigned long long idle_time;
	unsigned long psw_mask;

	trace_hardirqs_on();
	/* Don't trace preempt off for idle. */
	stop_critical_timings();

	/* Wait for external, I/O or machine check interrupt. */
	psw_mask = psw_kernel_bits \| PSW_MASK_WAIT \| PSW_MASK_DAT \|
	PSW_MASK_IO \| PSW_MASK_EXT \| PSW_MASK_MCHECK;
	idle->nohz_delay = 0;

	/* Call the assembler magic in entry.S */
	psw_idle(idle, psw_mask);

	/* Reenable preemption tracer. */
	start_critical_timings();

	/* Account time spent with enabled wait psw loaded as idle time. */
	idle->sequence++;
	smp_wmb();
	idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
	idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
	idle->idle_time += idle_time;
	idle->idle_count++;
	account_idle_time(idle_time);
	smp_wmb();
	idle->sequence++;
	}

	cputime64_t s390_get_idle_time(int cpu)
	{
	struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
	unsigned long long now, idle_enter, idle_exit;
	unsigned int sequence;

	do {
	now = get_clock();
	sequence = ACCESS_ONCE(idle->sequence);
	idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
	idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
	} while ((sequence & 1) \|\| (idle->sequence != sequence));
	return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
	}

	/*
	* 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 *tmp;

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

	/*
	* Handler for expired virtual CPU timer.
	*/
	static void virt_timer_expire(void)
	{
	struct vtimer_list timer, tmp;
	unsigned long elapsed;
	LIST_HEAD(cb_list);

	/* walk timer list, fire all expired timers */
	spin_lock(&virt_timer_lock);
	elapsed = atomic64_read(&virt_timer_elapsed);
	list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
	if (timer->expires < elapsed)
	/* move expired timer to the callback queue */
	list_move_tail(&timer->entry, &cb_list);
	else
	timer->expires -= elapsed;
	}
	if (!list_empty(&virt_timer_list)) {
	timer = list_first_entry(&virt_timer_list,
	struct vtimer_list, entry);
	atomic64_set(&virt_timer_current, timer->expires);
	}
	atomic64_sub(elapsed, &virt_timer_elapsed);
	spin_unlock(&virt_timer_lock);

	/* Do callbacks and recharge periodic timers */
	list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
	list_del_init(&timer->entry);
	timer->function(timer->data);
	if (timer->interval) {
	/* Recharge interval timer */
	timer->expires = timer->interval +
	atomic64_read(&virt_timer_elapsed);
	spin_lock(&virt_timer_lock);
	list_add_sorted(timer, &virt_timer_list);
	spin_unlock(&virt_timer_lock);
	}
	}
	}

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

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

	static void internal_add_vtimer(struct vtimer_list *timer)
	{
	if (list_empty(&virt_timer_list)) {
	/* First timer, just program it. */
	atomic64_set(&virt_timer_current, timer->expires);
	atomic64_set(&virt_timer_elapsed, 0);
	list_add(&timer->entry, &virt_timer_list);
	} else {
	/* Update timer against current base. */
	timer->expires += atomic64_read(&virt_timer_elapsed);
	if (likely((s64) timer->expires <
	(s64) atomic64_read(&virt_timer_current)))
	/* The new timer expires before the current timer. */
	atomic64_set(&virt_timer_current, timer->expires);
	/* Insert new timer into the list. */
	list_add_sorted(timer, &virt_timer_list);
	}
	}

	static void __add_vtimer(struct vtimer_list *timer, int periodic)
	{
	unsigned long flags;

	timer->interval = periodic ? timer->expires : 0;
	spin_lock_irqsave(&virt_timer_lock, flags);
	internal_add_vtimer(timer);
	spin_unlock_irqrestore(&virt_timer_lock, flags);
	}

	/*
	* add_virt_timer - add an oneshot virtual CPU timer
	*/
	void add_virt_timer(struct vtimer_list *timer)
	{
	__add_vtimer(timer, 0);
	}
	EXPORT_SYMBOL(add_virt_timer);

	/*
	* add_virt_timer_int - add an interval virtual CPU timer
	*/
	void add_virt_timer_periodic(struct vtimer_list *timer)
	{
	__add_vtimer(timer, 1);
	}
	EXPORT_SYMBOL(add_virt_timer_periodic);

	static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
	{
	unsigned long flags;
	int rc;

	BUG_ON(!timer->function);

	if (timer->expires == expires && vtimer_pending(timer))
	return 1;
	spin_lock_irqsave(&virt_timer_lock, flags);
	rc = vtimer_pending(timer);
	if (rc)
	list_del_init(&timer->entry);
	timer->interval = periodic ? expires : 0;
	timer->expires = expires;
	internal_add_vtimer(timer);
	spin_unlock_irqrestore(&virt_timer_lock, flags);
	return rc;
	}

	/*
	* returns whether it has modified a pending timer (1) or not (0)
	*/
	int mod_virt_timer(struct vtimer_list *timer, u64 expires)
	{
	return __mod_vtimer(timer, expires, 0);
	}
	EXPORT_SYMBOL(mod_virt_timer);

	/*
	* returns whether it has modified a pending timer (1) or not (0)
	*/
	int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
	{
	return __mod_vtimer(timer, expires, 1);
	}
	EXPORT_SYMBOL(mod_virt_timer_periodic);

	/*
	* 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;

	if (!vtimer_pending(timer))
	return 0;
	spin_lock_irqsave(&virt_timer_lock, flags);
	list_del_init(&timer->entry);
	spin_unlock_irqrestore(&virt_timer_lock, flags);
	return 1;
	}
	EXPORT_SYMBOL(del_virt_timer);

	/*
	* Start the virtual CPU timer on the current CPU.
	*/
	void __cpuinit init_cpu_vtimer(void)
	{
	/* set initial cpu timer */
	set_vtimer(VTIMER_MAX_SLICE);
	}

	static int __cpuinit s390_nohz_notify(struct notifier_block *self,
	unsigned long action, void *hcpu)
	{
	struct s390_idle_data *idle;
	long cpu = (long) hcpu;

	idle = &per_cpu(s390_idle, cpu);
	switch (action) {
	case CPU_DYING:
	case CPU_DYING_FROZEN:
	idle->nohz_delay = 0;
	default:
	break;
	}
	return NOTIFY_OK;
	}

	void __init vtime_init(void)
	{
	/* Enable cpu timer interrupts on the boot cpu. */
	init_cpu_vtimer();
	cpu_notifier(s390_nohz_notify, 0);
	}