1 files changed, 254 insertions, 421 deletions

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index c5f05b3fb2c..8c34363d6f1 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -1,185 +1,198 @@
 /*
- *  arch/s390/kernel/vtime.c
  *    Virtual cpu timer based timer functions.
  *
- *  S390 version
- *    Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ *    Copyright IBM Corp. 2004, 2012
  *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
  */
 
-#include <linux/module.h>
+#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/delay.h>
-#include <linux/init.h>
+#include <linux/cpu.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>
+#include <asm/cputime.h>
+#include <asm/vtimer.h>
+#include <asm/vtime.h>
+#include <asm/irq.h>
+#include "entry.h"
 
-static ext_int_info_t ext_int_info_timer;
-static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);
+static void virt_timer_expire(void);
 
-#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)
+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)
 {
-	cputime_t cputime;
-	__u64 timer, clock;
-	int rcu_user_flag;
+	u64 timer;
 
-	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);
-	}
+	asm volatile("stpt %0" : "=m" (timer));
+	return timer;
 }
 
-/*
- * 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)
+static inline void set_vtimer(u64 expires)
 {
-	cputime_t cputime;
-	__u64 timer;
+	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;
+	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;
+}
 
-	cputime = S390_lowcore.user_timer >> 12;
-	S390_lowcore.user_timer -= cputime << 12;
-	S390_lowcore.steal_clock -= cputime << 12;
-	account_user_time(tsk, cputime);
+static inline int virt_timer_forward(u64 elapsed)
+{
+	BUG_ON(!irqs_disabled());
 
-	cputime =  S390_lowcore.system_timer >> 12;
-	S390_lowcore.system_timer -= cputime << 12;
-	S390_lowcore.steal_clock -= cputime << 12;
-	account_system_time(tsk, 0, cputime);
+	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.
  */
-void account_system_vtime(struct task_struct *tsk)
+static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
 {
-	cputime_t cputime;
-	__u64 timer;
+	struct thread_info *ti = task_thread_info(tsk);
+	u64 timer, clock, user, system, steal;
 
 	timer = S390_lowcore.last_update_timer;
-	asm volatile ("  STPT %0"    /* Store current cpu timer value */
-		      : "=m" (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);
+	}
 
-	cputime =  S390_lowcore.system_timer >> 12;
-	S390_lowcore.system_timer -= cputime << 12;
-	S390_lowcore.steal_clock -= cputime << 12;
-	account_system_time(tsk, 0, cputime);
+	return virt_timer_forward(user + system);
 }
 
-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)
+void vtime_task_switch(struct task_struct *prev)
 {
-	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;
+	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(current);
+	S390_lowcore.user_timer = ti->user_timer;
+	S390_lowcore.system_timer = ti->system_timer;
 }
-#endif
 
-static void start_cpu_timer(void)
+/*
+ * In s390, accounting pending user time also implies
+ * accounting system time in order to correctly compute
+ * the stolen time accounting.
+ */
+void vtime_account_user(struct task_struct *tsk)
 {
-	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);
+	if (do_account_vtime(tsk, HARDIRQ_OFFSET))
+		virt_timer_expire();
 }
 
-static void stop_cpu_timer(void)
+/*
+ * Update process times based on virtual cpu times stored by entry.S
+ * to the lowcore fields user_timer, system_timer & steal_clock.
+ */
+void vtime_account_irq_enter(struct task_struct *tsk)
 {
-	struct vtimer_queue *vt_list;
+	struct thread_info *ti = task_thread_info(tsk);
+	u64 timer, system;
 
-	vt_list = &__get_cpu_var(virt_cpu_timer);
+	WARN_ON_ONCE(!irqs_disabled());
 
-	/* nothing to do */
-	if (list_empty(&vt_list->list)) {
-		vt_list->idle = VTIMER_MAX_SLICE;
-		goto fire;
-	}
+	timer = S390_lowcore.last_update_timer;
+	S390_lowcore.last_update_timer = get_vtimer();
+	S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
 
-	/* store the actual expire value */
-	asm volatile ("STPT %0" : "=m" (vt_list->idle));
+	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);
 
-	/*
-	 * 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;
+	virt_timer_forward(system);
+}
+EXPORT_SYMBOL_GPL(vtime_account_irq_enter);
 
-	vt_list->offset += vt_list->to_expire - vt_list->idle;
+void vtime_account_system(struct task_struct *tsk)
+__attribute__((alias("vtime_account_irq_enter")));
+EXPORT_SYMBOL_GPL(vtime_account_system);
 
-	/*
-	 * 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);
+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();
+
+	/* 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);
+
+	/* 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_tod_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) || (ACCESS_ONCE(idle->sequence) != sequence));
+	return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
 }
 
 /*
@@ -188,11 +201,11 @@ static void stop_cpu_timer(void)
  */
 static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
 {
-	struct vtimer_list *event;
+	struct vtimer_list *tmp;
 
-	list_for_each_entry(event, head, entry) {
-		if (event->expires > timer->expires) {
-			list_add_tail(&timer->entry, &event->entry);
+	list_for_each_entry(tmp, head, entry) {
+		if (tmp->expires > timer->expires) {
+			list_add_tail(&timer->entry, &tmp->entry);
 			return;
 		}
 	}
@@ -200,312 +213,158 @@ static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
 }
 
 /*
- * Do the callback functions of expired vtimer events.
- * Called from within the interrupt handler.
+ * Handler for expired virtual CPU timer.
  */
-static void do_callbacks(struct list_head *cb_list)
+static void virt_timer_expire(void)
 {
-	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);
-		}
+	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;
 	}
-}
-
-/*
- * 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);
+	if (!list_empty(&virt_timer_list)) {
+		timer = list_first_entry(&virt_timer_list,
+					 struct vtimer_list, entry);
+		atomic64_set(&virt_timer_current, timer->expires);
 	}
-	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;
+	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);
+		}
 	}
-	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));
+	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);
-
-	if (timer->cpu != smp_processor_id())
-		printk("internal_add_vtimer: BUG, running on wrong CPU");
-
-	/* 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;
+	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);
 	}
-
-	/* 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 int prepare_vtimer(struct vtimer_list *timer)
+static void __add_vtimer(struct vtimer_list *timer, int periodic)
 {
-	if (!timer->function) {
-		printk("add_virt_timer: uninitialized timer\n");
-		return -EINVAL;
-	}
-
-	if (!timer->expires || timer->expires > VTIMER_MAX_SLICE) {
-		printk("add_virt_timer: invalid timer expire value!\n");
-		return -EINVAL;
-	}
-
-	if (vtimer_pending(timer)) {
-		printk("add_virt_timer: timer pending\n");
-		return -EBUSY;
-	}
+	unsigned long flags;
 
-	timer->cpu = get_cpu();
-	return 0;
+	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(void *new)
+void add_virt_timer(struct vtimer_list *timer)
 {
-	struct vtimer_list *timer;
-
-	timer = (struct vtimer_list *)new;
-
-	if (prepare_vtimer(timer) < 0)
-		return;
-
-	timer->interval = 0;
-	internal_add_vtimer(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(void *new)
+void add_virt_timer_periodic(struct vtimer_list *timer)
 {
-	struct vtimer_list *timer;
-
-	timer = (struct vtimer_list *)new;
-
-	if (prepare_vtimer(timer) < 0)
-		return;
-
-	timer->interval = timer->expires;
-	internal_add_vtimer(timer);
+	__add_vtimer(timer, 1);
 }
 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)
+static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
 {
-	struct vtimer_queue *vt_list;
 	unsigned long flags;
-	int cpu;
+	int rc;
 
-	if (!timer->function) {
-		printk("mod_virt_timer: uninitialized timer\n");
-		return	-EINVAL;
-	}
-
-	if (!expires || expires > VTIMER_MAX_SLICE) {
-		printk("mod_virt_timer: invalid expire range\n");
-		return -EINVAL;
-	}
+	BUG_ON(!timer->function);
 
-	/*
-	 * 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);
-
-	/* 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;
-	}
-
-	/* check if we run on the right CPU */
-	if (timer->cpu != cpu) {
-		printk("mod_virt_timer: running on wrong CPU, check your code\n");
-		spin_unlock_irqrestore(&vt_list->lock, flags);
-		put_cpu();
-		return -EINVAL;
-	}
-
-	list_del_init(&timer->entry);
+	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;
-
-	/* 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;
+	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);
 
 /*
- * delete a virtual 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;
-	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! */
+	spin_lock_irqsave(&virt_timer_lock, flags);
 	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);
+	spin_unlock_irqrestore(&virt_timer_lock, flags);
 	return 1;
 }
 EXPORT_SYMBOL(del_virt_timer);
@@ -515,55 +374,29 @@ EXPORT_SYMBOL(del_virt_timer);
  */
 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;
-
+	/* set initial cpu timer */
+	set_vtimer(VTIMER_MAX_SLICE);
 }
 
-static int vtimer_idle_notify(struct notifier_block *self,
-			      unsigned long action, void *hcpu)
+static int s390_nohz_notify(struct notifier_block *self, unsigned long action,
+			    void *hcpu)
 {
-	switch (action) {
-	case S390_CPU_IDLE:
-		stop_cpu_timer();
-		break;
-	case S390_CPU_NOT_IDLE:
-		start_cpu_timer();
+	struct s390_idle_data *idle;
+	long cpu = (long) hcpu;
+
+	idle = &per_cpu(s390_idle, cpu);
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_DYING:
+		idle->nohz_delay = 0;
+	default:
 		break;
 	}
 	return NOTIFY_OK;
 }
 
-static struct notifier_block vtimer_idle_nb = {
-	.notifier_call = vtimer_idle_notify,
-};
-
 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");
-
-	if (register_idle_notifier(&vtimer_idle_nb))
-		panic("Couldn't register idle notifier");
-
 	/* Enable cpu timer interrupts on the boot cpu. */
 	init_cpu_vtimer();
+	cpu_notifier(s390_nohz_notify, 0);
 }
-