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[PATCH] 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 <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Martin Schwidefsky 2005-11-07 00:59:02 -08:00 committed by Linus Torvalds
parent e1c3ad96f6
commit 1b44e98d7d
1 changed files with 7 additions and 1 deletions
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8
arch/s390/kernel/time.c
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@ -237,6 +237,8 @@ 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)
@ -257,7 +259,11 @@ 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)) {