From: Martin Schwidefsky <[email protected]>
[patch 3/14] s390: stop_hz_timer vs. xtime updates.
The calculation of the value return by next_timer_interrupt from
jiffies to jiffies_64 is racy against xtime updates. We need to
protect the calculation with read_seqbegin/read_seqretry.
Signed-off-by: Martin Schwidefsky <[email protected]>
---
arch/s390/kernel/time.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletion(-)
diff -urpN linux-2.6/arch/s390/kernel/time.c linux-2.6-patched/arch/s390/kernel/time.c
--- linux-2.6/arch/s390/kernel/time.c 2005-10-28 02:02:08.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/time.c 2005-10-28 14:04:45.000000000 +0200
@@ -241,6 +241,8 @@ int sysctl_hz_timer = 1;
*/
static inline void stop_hz_timer(void)
{
+ unsigned long flags;
+ unsigned long seq, next;
__u64 timer, todval;
if (sysctl_hz_timer != 0)
@@ -261,7 +263,11 @@ static inline void stop_hz_timer(void)
* This cpu is going really idle. Set up the clock comparator
* for the next event.
*/
- timer = (__u64) (next_timer_interrupt() - jiffies) + jiffies_64;
+ next = next_timer_interrupt();
+ do {
+ seq = read_seqbegin_irqsave(&xtime_lock, flags);
+ timer = (__u64)(next - jiffies) + jiffies_64;
+ } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
todval = -1ULL;
/* Be careful about overflows. */
if (timer < (-1ULL / CLK_TICKS_PER_JIFFY)) {