Fix up jiffy comparison function in the scheduler.

The jiffy comparison in reblance_tick() has always used a simple integer
comparison and I have followed that convention for the patchset that
rebalances sched domains via a tasklet.

However, jiffies may wrap around zero. If we do not use the time_after()
function then comparisons may not give the intended results.

Fix this up by using jiffy comparison functions.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc4-mm2/kernel/sched.c
===================================================================
--- linux-2.6.19-rc4-mm2.orig/kernel/sched.c	2006-11-06 13:53:52.366233053 -0600
+++ linux-2.6.19-rc4-mm2/kernel/sched.c	2006-11-06 13:58:38.467745413 -0600
@@ -2766,8 +2766,10 @@ static void idle_balance(int this_cpu, s
 			/* If we've pulled tasks over stop searching: */
 			pulled_task = load_balance_newidle(this_cpu,
 							this_rq, sd);
-			next_balance = min(next_balance,
-				sd->last_balance + sd->balance_interval);
+			if (time_after(next_balance,
+				  sd->last_balance + sd->balance_interval))
+				next_balance = sd->last_balance
+						+ sd->balance_interval;
 			if (pulled_task)
 				break;
 		}
@@ -2891,7 +2893,7 @@ static void rebalance_domains(unsigned l
 		if (unlikely(!interval))
 			interval = 1;
 
-		if (jiffies - sd->last_balance >= interval) {
+		if (time_after_eq(jiffies, sd->last_balance + interval)) {
 			if (load_balance(this_cpu, this_rq, sd, idle)) {
 				/*
 				 * We've pulled tasks over so either we're no
@@ -2910,8 +2912,8 @@ static void rebalance_domains(unsigned l
 		 * then idle_balance will reset next_balance so that we
 		 * rebalance earlier.
 		 */
-		next_balance = min(next_balance,
-				sd->last_balance + interval);
+		if (time_after(next_balance, sd->last_balance + interval))
+			next_balance = sd->last_balance + interval;
 	}
 	this_rq->next_balance = next_balance;
 }
@@ -3168,7 +3170,7 @@ void scheduler_tick(void)
 		task_running_tick(rq, p);
 #ifdef CONFIG_SMP
 	update_load(rq);
-	if (jiffies >= rq->next_balance)
+	if (time_after_eq(jiffies, rq->next_balance))
 		tasklet_schedule(&rebalance);
 #endif
 }