[S390] extend virtual timer interface by mod_virt_timer_periodic

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>

2 files changed, 34 insertions, 24 deletions

diff --git a/arch/s390/include/asm/timer.h b/arch/s390/include/asm/timer.h
index e4bcab739c1..814243cafdf 100644
--- a/arch/s390/include/asm/timer.h
+++ b/arch/s390/include/asm/timer.h
@@ -41,6 +41,7 @@ extern void init_virt_timer(struct vtimer_list *timer);
 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);
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index ecf0304e61c..694b44374a2 100644
--- a/arch/s390/kernel/vtime.c
+++ b/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 *timer, __u64 expires)
         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 *timer, __u64 expires)
         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)