Re: [PATCH]sched: Isochronous class v2 for unprivileged soft rtscheduling

[Alexander Nyberg]

> My simple yield DoS don't work anymore. But i found another way.
> Running this as SCHED_ISO:

Yep, bad accounting in queue_iso() which relied on p->array == rq->active
This fixes it:


Index: vanilla/kernel/sched.c
===================================================================
--- vanilla.orig/kernel/sched.c	2005-01-20 18:05:59.000000000 +0100
+++ vanilla/kernel/sched.c	2005-01-20 18:41:26.000000000 +0100
@@ -2621,15 +2621,19 @@
 static task_t* queue_iso(runqueue_t *rq, prio_array_t *array)
 {
 	task_t *p = list_entry(rq->iso_queue.next, task_t, iso_list);
-	if (p->prio == MAX_RT_PRIO)
-		goto out;
+	prio_array_t *old_array = p->array;
+	
+	old_array->nr_active--;
 	list_del(&p->run_list);
-	if (list_empty(array->queue + p->prio))
-		__clear_bit(p->prio, array->bitmap);
+	if (list_empty(old_array->queue + p->prio))
+		__clear_bit(p->prio, old_array->bitmap);
+	
 	p->prio = MAX_RT_PRIO;
 	list_add_tail(&p->run_list, array->queue + p->prio);
 	__set_bit(p->prio, array->bitmap);
-out:
+	array->nr_active++;
+	p->array = array;
+	
 	return p;
 }
 


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