[PATCH] s390: idle timer setup

Fix overflow in calculation of the new tod value in stop_hz_timer and fix
wrong virtual timer list idle time in case the virtual timer is already
expired in stop_cpu_timer.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 22 insertions, 15 deletions

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 061e81138dc2..8ca485676780 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -244,7 +244,7 @@ int sysctl_hz_timer = 1;
  */
 static inline void stop_hz_timer(void)
 {
-        __u64 timer;
+        __u64 timer, todval;
 
         if (sysctl_hz_timer != 0)
                 return;
@@ -265,8 +265,14 @@ static inline void stop_hz_timer(void)
          * for the next event.
          */
         timer = (__u64) (next_timer_interrupt() - jiffies) + jiffies_64;
-        timer = jiffies_timer_cc + timer * CLK_TICKS_PER_JIFFY;
-        asm volatile ("SCKC %0" : : "m" (timer));
+        todval = -1ULL;
+        /* Be careful about overflows. */
+        if (timer < (-1ULL / CLK_TICKS_PER_JIFFY)) {
+                timer = jiffies_timer_cc + timer * CLK_TICKS_PER_JIFFY;
+                if (timer >= jiffies_timer_cc)
+                        todval = timer;
+        }
+        asm volatile ("SCKC %0" : : "m" (todval));
 }
 
 /*
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index bb6cf02418a2..fa0726507b3d 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -122,12 +122,17 @@ static void start_cpu_timer(void)
         struct vtimer_queue *vt_list;
 
         vt_list = &per_cpu(virt_cpu_timer, smp_processor_id());
-        set_vtimer(vt_list->idle);
+
+        /* 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);
 }
 
 static void stop_cpu_timer(void)
 {
-        __u64 done;
         struct vtimer_queue *vt_list;
 
         vt_list = &per_cpu(virt_cpu_timer, smp_processor_id());
@@ -138,21 +143,17 @@ static void stop_cpu_timer(void)
                 goto fire;
         }
 
-        /* store progress */
-        asm volatile ("STPT %0" : "=m" (done));
+        /* store the actual expire value */
+        asm volatile ("STPT %0" : "=m" (vt_list->idle));
 
         /*
-         * If done is negative we do not stop the CPU timer
-         * because we will get instantly an interrupt that
-         * will start the CPU timer again.
+         * If the CPU timer is negative we don't reprogramm
+         * it because we will get instantly an interrupt.
          */
-        if (done & 1LL<<63)
+        if (vt_list->idle & 1LL<<63)
                 return;
-        else
-                vt_list->offset += vt_list->to_expire - done;
 
-        /* save the actual expire value */
-        vt_list->idle = done;
+        vt_list->offset += vt_list->to_expire - vt_list->idle;
 
         /*
          * We cannot halt the CPU timer, we just write a value that