This patch fixes a divide-by-zero error that I hit on a two-way i386
machine. rq->nr_running is tested to be non-zero, but may change by the
time it is used in the division. Saving the value to a local variable
ensures that the same value that is checked is used in the division.
Signed-off-by: Dave Kleikamp <[email protected]>
Cc: Con Kolivas <[email protected]>
diff -urp linux-2.6.13-rc5-mm1/kernel/sched.c linux/kernel/sched.c
--- linux-2.6.13-rc5-mm1/kernel/sched.c 2005-08-11 09:41:30.000000000 -0500
+++ linux/kernel/sched.c 2005-08-11 09:47:27.000000000 -0500
@@ -989,15 +989,16 @@ void kick_process(task_t *p)
static inline unsigned long __source_load(int cpu, int type, enum idle_type idle)
{
runqueue_t *rq = cpu_rq(cpu);
+ unsigned long running = rq->nr_running;
unsigned long source_load, cpu_load = rq->cpu_load[type-1],
- load_now = rq->nr_running * SCHED_LOAD_SCALE;
+ load_now = running * SCHED_LOAD_SCALE;
if (type == 0)
source_load = load_now;
else
source_load = min(cpu_load, load_now);
- if (rq->nr_running > 1 || (idle == NOT_IDLE && rq->nr_running))
+ if (running > 1 || (idle == NOT_IDLE && running))
/*
* If we are busy rebalancing the load is biased by
* priority to create 'nice' support across cpus. When
@@ -1006,7 +1007,7 @@ static inline unsigned long __source_loa
* prevent idle rebalance from trying to pull tasks from a
* queue with only one running task.
*/
- source_load = source_load * rq->prio_bias / rq->nr_running;
+ source_load = source_load * rq->prio_bias / running;
return source_load;
}
@@ -1022,16 +1023,17 @@ static inline unsigned long source_load(
static inline unsigned long __target_load(int cpu, int type, enum idle_type idle)
{
runqueue_t *rq = cpu_rq(cpu);
+ unsigned long running = rq->nr_running;
unsigned long target_load, cpu_load = rq->cpu_load[type-1],
- load_now = rq->nr_running * SCHED_LOAD_SCALE;
+ load_now = running * SCHED_LOAD_SCALE;
if (type == 0)
target_load = load_now;
else
target_load = max(cpu_load, load_now);
- if (rq->nr_running > 1 || (idle == NOT_IDLE && rq->nr_running))
- target_load = target_load * rq->prio_bias / rq->nr_running;
+ if (running > 1 || (idle == NOT_IDLE && running))
+ target_load = target_load * rq->prio_bias / running;
return target_load;
}
--
David Kleikamp
IBM Linux Technology Center
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