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Subject[081/114] time: Workaround gcc loop optimization that causes 64bit div errors
2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------
From: John Stultz <johnstul@us.ibm.com>

commit c7dcf87a6881bf796faee83003163eb3de41a309 upstream.

Early 4.3 versions of gcc apparently aggressively optimize the raw
time accumulation loop, replacing it with a divide.

On 32bit systems, this causes the following link errors:
undefined reference to `__umoddi3'
undefined reference to `__udivdi3'

The gcc issue has been fixed in 4.4 and greater.

This patch replaces the accumulation loop with a do_div, as suggested
by Linus.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
CC: Jason Wessel <jason.wessel@windriver.com>
CC: Larry Finger <Larry.Finger@lwfinger.net>
CC: Ingo Molnar <mingo@elte.hu>
CC: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/time/timekeeping.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -756,9 +756,10 @@ static cycle_t logarithmic_accumulation(
/* Accumulate raw time */
raw_nsecs = timekeeper.raw_interval << shift;
raw_nsecs += raw_time.tv_nsec;
- while (raw_nsecs >= NSEC_PER_SEC) {
- raw_nsecs -= NSEC_PER_SEC;
- raw_time.tv_sec++;
+ if (raw_nsecs >= NSEC_PER_SEC) {
+ u64 raw_secs = raw_nsecs;
+ raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
+ raw_time.tv_sec += raw_secs;
}
raw_time.tv_nsec = raw_nsecs;




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