We get
kernel/built-in.o: In function `load_balance':
/tmp/distcc_1108/kernel/sched.c:1188: undefined reference to `__udivdi3'
Because CAN_MIGRATE_TASK's use of NS_TO_JIFFIES requires a 64-bit divide.
Fix that by using JIFFIES_TO_NS on the rhs of the expression instead, and
rework it to make the code more understandable.
kernel/sched.c | 32 ++++++++++++++++++++++++--------
1 files changed, 24 insertions(+), 8 deletions(-)
diff -puN kernel/sched.c~o14int-div-fix kernel/sched.c
--- 25/kernel/sched.c~o14int-div-fix 2003-08-30 15:42:03.000000000 -0700
+++ 25-akpm/kernel/sched.c 2003-08-30 15:42:03.000000000 -0700
@@ -1129,6 +1129,29 @@ static inline void pull_task(runqueue_t
}
/*
+ * Previously:
+ *
+ * #define CAN_MIGRATE_TASK(p,rq,this_cpu) \
+ * ((!idle || (NS_TO_JIFFIES(now - (p)->timestamp) > \
+ * cache_decay_ticks)) && !task_running(rq, p) && \
+ * cpu_isset(this_cpu, (p)->cpus_allowed))
+ */
+
+static inline int
+can_migrate_task(task_t *tsk, runqueue_t *rq, int this_cpu, int idle)
+{
+ unsigned long delta = sched_clock() - tsk->timestamp;
+
+ if (!idle && (delta <= JIFFIES_TO_NS(cache_decay_ticks)))
+ return 0;
+ if (task_running(rq, tsk))
+ return 0;
+ if (!cpu_isset(this_cpu, tsk->cpus_allowed))
+ return 0;
+ return 1;
+}
+
+/*
* Current runqueue is empty, or rebalance tick: if there is an
* inbalance (current runqueue is too short) then pull from
* busiest runqueue(s).
@@ -1142,14 +1165,12 @@ static void load_balance(runqueue_t *thi
runqueue_t *busiest;
prio_array_t *array;
struct list_head *head, *curr;
- unsigned long long now;
task_t *tmp;
busiest = find_busiest_queue(this_rq, this_cpu, idle, &imbalance, cpumask);
if (!busiest)
goto out;
- now = sched_clock();
/*
* We only want to steal a number of tasks equal to 1/2 the imbalance,
* otherwise we'll just shift the imbalance to the new queue:
@@ -1195,14 +1216,9 @@ skip_queue:
* 3) are cache-hot on their current CPU.
*/
-#define CAN_MIGRATE_TASK(p,rq,this_cpu) \
- ((idle || (NS_TO_JIFFIES(now - (p)->timestamp) > \
- cache_decay_ticks)) && !task_running(rq, p) && \
- cpu_isset(this_cpu, (p)->cpus_allowed))
-
curr = curr->prev;
- if (!CAN_MIGRATE_TASK(tmp, busiest, this_cpu)) {
+ if (!can_migrate_task(tmp, busiest, this_cpu, idle)) {
if (curr != head)
goto skip_queue;
idx++;
_