[PATCH] sched: prevent compiler from optimising sched_avg_update loop

GCC 4.4.1 on ARM has been observed to replace the while loop
in sched_avg_update with a call to uldivmod, resulting in the
following build failure at link-time:

kernel/built-in.o: In function `sched_avg_update':
/linux-2.6/kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
/linux-2.6/kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
make: *** [.tmp_vmlinux1] Error 1

This patch [taken against 2.6.34-rc2] replaces the loop with a call to
div_s64 which allows the Kernel to link.

Cc: Catalin Marinas <catalin.marinas <at> arm.com>
Cc: Ingo Molnar <mingo <at> elte.hu>
Cc: Andrew Morton <akpm <at> linux-foundation.org>
Cc: Peter Zijlstra <peterz <at> infradead.org>
Signed-off-by: Will Deacon <will.deacon <at> arm.com>
---
 kernel/sched.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 9ab3cd7..6b74f21 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
 <at>  <at>  -1238,11 +1238,10  <at>  <at>  static u64 sched_avg_period(void)
 static void sched_avg_update(struct rq *rq)
 {
 	s64 period = sched_avg_period();
+	s64 elapsed_periods = div_s64(rq->clock - rq->age_stamp - 1, period);