[PATCH 2/2] sched: Fix "divide error: 0000" in find_busiest_group

[Terry Loftin <terry.loftin@hp.com>]

Add a check to sched_avg_update() to detect and reset age_stamp if the
clock value has wrapped.  Because __cycles_2_ns() includes an offset
to account for start up time, the clock may not wrap to zero, so use
the current clock value instead.

Signed-off-by: Terry Loftin <terry.loftin@hp.com>
Signed-off-by: Bob Montgomery <bob.montgomery@hp.com>
---
diff --git a/kernel/sched.c b/kernel/sched.c
index 18d38e4..b39cae1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1256,6 +1256,8 @@ static void sched_avg_update(struct rq *rq)
 {
 	s64 period = sched_avg_period();

+	if (unlikely(rq->age_stamp > rq->clock))
+		rq->age_stamp = rq->clock;
 	while ((s64)(rq->clock - rq->age_stamp) > period) {
 		/*
 		 * Inline assembly required to prevent the compiler