Re: Kaffeine problem with CFS

Ingo Molnar
2007-04-18T15:48:23Z

* S.Çağlar Onur <caglar@pardus.org.tr> wrote:

> - schedule();
> + msleep(1);

> which Ingo sends me to try also has the same effect on me. I cannot
> reproduce hangs anymore with that patch applied top of CFS while one
> console checks out SVN repos and other one compiles a small test
> software.

great! Could you please unapply the hack above and try the proper fix
below, does this one solve the hangs too?

Ingo

Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -264,15 +264,26 @@ static void dequeue_task_fair(struct rq

/*
* sched_yield() support is very simple via the rbtree, we just
- * dequeue and enqueue the task, which causes the task to
- * roundrobin to the end of the tree:
+ * dequeue the task and move it to the rightmost position, which
+ * causes the task to roundrobin to the end of the tree.
*/
static void requeue_task_fair(struct rq *rq, struct task_struct *p)
{
dequeue_task_fair(rq, p);
p->on_rq = 0;
- enqueue_task_fair(rq, p);
+ /*
+ * Temporarily insert at the last position of the tree:
+ */
+ p->fair_key = LLONG_MAX;
+ __enqueue_task_fair(rq, p);
p->on_rq = 1;
+
+ /*
+ * Update the key to the real value, so that when all other
+ * tasks from before the rightmost position have executed,
+ * this task is picked up again:
+ */
+ p->fair_key = rq->fair_clock - p->wait_runtime + p->nice_offset;
}

/*
@@ -380,7 +391,10 @@ static void task_tick_fair(struct rq *rq
* Dequeue and enqueue the task to update its
* position within the tree:
*/
- requeue_task_fair(rq, curr);
+ dequeue_task_fair(rq, curr);
+ curr->on_rq = 0;
+ enqueue_task_fair(rq, curr);
+ curr->on_rq = 1;

/*
* Reschedule if another task tops the current one.