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Subject[patch 05/14] extend virtual timer interface by mod_virt_timer_periodic
From: Jan Glauber <jang@linux.vnet.ibm.com>

In case mod_virt_timer is used to add a non pending timer the timer
is always added as a one-shot timer. If mod_virt_timer is used for
periodic timers they may therfore be degraded to one-shot timers.

Add mod_virt_timer_periodic to the interface to allow safe re-programming
of the interval value.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/include/asm/timer.h | 1
arch/s390/kernel/vtime.c | 57 ++++++++++++++++++++++++------------------
2 files changed, 34 insertions(+), 24 deletions(-)
Index: quilt-2.6/arch/s390/include/asm/timer.h
===================================================================
--- quilt-2.6.orig/arch/s390/include/asm/timer.h
+++ quilt-2.6/arch/s390/include/asm/timer.h
@@ -41,6 +41,7 @@ extern void init_virt_timer(struct vtime
extern void add_virt_timer(void *new);
extern void add_virt_timer_periodic(void *new);
extern int mod_virt_timer(struct vtimer_list *timer, __u64 expires);
+extern int mod_virt_timer_periodic(struct vtimer_list *timer, __u64 expires);
extern int del_virt_timer(struct vtimer_list *timer);

extern void init_cpu_vtimer(void);
Index: quilt-2.6/arch/s390/kernel/vtime.c
===================================================================
--- quilt-2.6.orig/arch/s390/kernel/vtime.c
+++ quilt-2.6/arch/s390/kernel/vtime.c
@@ -425,17 +425,7 @@ void add_virt_timer_periodic(void *new)
}
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)
+int __mod_vtimer(struct vtimer_list *timer, __u64 expires, int periodic)
{
struct vtimer_queue *vq;
unsigned long flags;
@@ -444,39 +434,35 @@ int mod_virt_timer(struct vtimer_list *t
BUG_ON(!timer->function);
BUG_ON(!expires || expires > VTIMER_MAX_SLICE);

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

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

- /* check if we run on the right CPU */
- BUG_ON(timer->cpu != cpu);
-
/* disable interrupts before test if timer is pending */
spin_lock_irqsave(&vq->lock, flags);

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

+ /* check if we run on the right CPU */
+ BUG_ON(timer->cpu != cpu);
+
list_del_init(&timer->entry);
timer->expires = expires;
-
- /* also change the interval if we have an interval timer */
- if (timer->interval)
+ if (periodic)
timer->interval = expires;

/* the timer can't expire anymore so we can release the lock */
@@ -484,9 +470,32 @@ int mod_virt_timer(struct vtimer_list *t
internal_add_vtimer(timer);
return 1;
}
+
+/*
+ * If we change a pending timer the function must be called on the CPU
+ * where the timer is running on.
+ *
+ * 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);

/*
+ * If we change a pending timer the function must be called on the CPU
+ * where the timer is running on.
+ *
+ * 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)
--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.



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