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Commit c7dcf87a authored by John Stultz's avatar John Stultz Committed by Linus Torvalds
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time: Workaround gcc loop optimization that causes 64bit div errors 



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: default avatarJohn 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2be1f3a7

kernel/time/timekeeping.c

+4 −3
Original line number Diff line number Diff line
@@ -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;