On Sun, May 21, 2006 at 09:00:51PM +0000, Linux Kernel wrote:
> commit 92f63cd000059366af18712367216d96180e0ec0
> tree 4f88c3875afaa8183d6cfcff685e03ac7684d82d
> parent 0662b71322e211dba9a4bc0e6fbca7861a2b5a7d
> author Martin Schwidefsky <[email protected]> Sun, 21 May 2006 05:00:25 -0700
> committer Linus Torvalds <[email protected]> Mon, 22 May 2006 02:59:21 -0700
>
> [PATCH] s390: next_timer_interrupt overflow in stop_hz_timer
>
> The 32 bit unsigned substraction (next - jiffies) in stop_hz_timer can
> overflow if jiffies gets advanced between next_timer_interrupt and the read
> under the xtime lock. The cast to a u64 then results in a large value
> which causes the cpu to wait too long. Fix this by casting next and
> jiffies independently to u64 before subtracting them.
>
> (Spotted by Zachary Amsden <[email protected]>)
>
> Signed-off-by: Martin Schwidefsky <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> Signed-off-by: Linus Torvalds <[email protected]>
>
> arch/s390/kernel/time.c | 2 +-
> 1 files changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
> index 029f099..ce19ad4 100644
> --- a/arch/s390/kernel/time.c
> +++ b/arch/s390/kernel/time.c
> @@ -272,7 +272,7 @@ static inline void stop_hz_timer(void)
> next = next_timer_interrupt();
> do {
> seq = read_seqbegin_irqsave(&xtime_lock, flags);
> - timer = (__u64)(next - jiffies) + jiffies_64;
> + timer = (__u64 next) - (__u64 jiffies) + jiffies_64;
> } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
> todval = -1ULL;
> /* Be careful about overflows. */
arch/s390/kernel/time.c: In function 'stop_hz_timer':
arch/s390/kernel/time.c:275: error: expected ')' before 'next'
arch/s390/kernel/time.c:275: error: expected ')' before 'jiffies'
Dave
--
http://www.codemonkey.org.uk
On Mon, 2006-05-22 at 16:14 -0400, Dave Jones wrote:
> arch/s390/kernel/time.c: In function 'stop_hz_timer':
> arch/s390/kernel/time.c:275: error: expected ')' before 'next'
> arch/s390/kernel/time.c:275: error: expected ')' before 'jiffies'
Argh,
I really have to stop doing things in a hurry. This result in stupid
things like missing parentheses for a type cast.
blue skies,
Martin.
Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH
"Reality continues to ruin my life." - Calvin.
--
From: Martin Schwidefsky <[email protected]>
[patch] s390: fix typo in stop_hz_timer.
Add missing parentheses for type cast to u64.
Signed-off-by: Martin Schwidefsky <[email protected]>
---
arch/s390/kernel/time.c | 2 +-
1 files changed, 1 insertion(+), 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 2006-05-23 09:10:41.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/time.c 2006-05-23 09:04:47.000000000 +0200
@@ -273,7 +273,7 @@ static inline void stop_hz_timer(void)
next = next_timer_interrupt();
do {
seq = read_seqbegin_irqsave(&xtime_lock, flags);
- timer = (__u64 next) - (__u64 jiffies) + jiffies_64;
+ timer = ((__u64) next) - ((__u64) jiffies) + jiffies_64;
} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
todval = -1ULL;
/* Be careful about overflows. */