[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>

1 files changed, 9 insertions, 3 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));
 }
 
 /*