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From: John Stultz on 13 Aug 2010 14:40
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(a)us.ibm.com>
CC: Jason Wessel <jason.wessel(a)windriver.com>
CC: Larry Finger <Larry.Finger(a)lwfinger.net>
CC: Ingo Molnar <mingo(a)elte.hu>
CC: Linus Torvalds <torvalds(a)linux-foundation.org>
---
kernel/time/timekeeping.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e960d82..49010d8 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -710,9 +710,10 @@ static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
/* 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;

--
1.6.0.4

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