[patch] sched-rebalance-fix-2.5.69-A1

From: Ingo Molnar (mingo@elte.hu)
Date: Mon May 19 2003 - 03:43:49 EST


the attached patch fixes a race noticed by Mike Galbraith: the scheduler
can lose a rebalance tick if some task happens to not be rescheduled in
time. This is not a fatal condition, but an inconsistency nevertheless.

        Ingo

--- linux/kernel/sched.c.orig
+++ linux/kernel/sched.c
@@ -1180,7 +1180,7 @@ void scheduler_tick(int user_ticks, int
         /* Task might have expired already, but not scheduled off yet */
         if (p->array != rq->active) {
                 set_tsk_need_resched(p);
- return;
+ goto out;
         }
         spin_lock(&rq->lock);
         /*
@@ -1207,7 +1207,7 @@ void scheduler_tick(int user_ticks, int
                         dequeue_task(p, rq->active);
                         enqueue_task(p, rq->active);
                 }
- goto out;
+ goto out_unlock;
         }
         if (!--p->time_slice) {
                 dequeue_task(p, rq->active);
@@ -1223,8 +1223,9 @@ void scheduler_tick(int user_ticks, int
                 } else
                         enqueue_task(p, rq->active);
         }
-out:
+out_unlock:
         spin_unlock(&rq->lock);
+out:
         rebalance_tick(rq, 0);
 }
 

-
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