Re: 2.6.21-rc5-mm4

[Con Kolivas <kernel@kolivas.org>]

On Thursday 05 April 2007 08:10, Andrew Morton wrote:
> Thanks - that'll be the CPU scheduler changes.
>
> Con has produced a patch or two which might address this but afaik we don't
> yet have a definitive fix?
>
> I believe that reverting
> sched-implement-staircase-deadline-cpu-scheduler-staircase-improvements.pat
>ch will prevent it.

I posted a definitive fix which Michal tested for me offlist. Subject was:
 [PATCH] sched: implement staircase deadline cpu scheduler improvements fix

Sorry about relative noise prior to that. Akpm please pick it up.

Here again just in case.

---
Use of memset was bogus. Fix it.

Fix exiting recalc_task_prio without p->array being updated.

Microoptimisation courtesy of Dmitry Adamushko <dmitry.adamushko@gmail.com>

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
 kernel/sched.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

Index: linux-2.6.21-rc5-mm4/kernel/sched.c
===================================================================
--- linux-2.6.21-rc5-mm4.orig/kernel/sched.c	2007-04-04 12:14:29.000000000 +1000
+++ linux-2.6.21-rc5-mm4/kernel/sched.c	2007-04-04 12:49:39.000000000 +1000
@@ -683,11 +683,13 @@ static void dequeue_task(struct task_str
  * The task is being queued on a fresh array so it has its entitlement
  * bitmap cleared.
  */
-static inline void task_new_array(struct task_struct *p, struct rq *rq)
+static void task_new_array(struct task_struct *p, struct rq *rq,
+			   struct prio_array *array)
 {
 	bitmap_zero(p->bitmap, PRIO_RANGE);
 	p->rotation = rq->prio_rotation;
 	p->time_slice = p->quota;
+	p->array = array;
 }
 
 /* Find the first slot from the relevant prio_matrix entry */
@@ -709,6 +711,8 @@ static inline int next_entitled_slot(str
 	DECLARE_BITMAP(tmp, PRIO_RANGE);
 	int search_prio, uprio = USER_PRIO(p->static_prio);
 
+	if (!rq->prio_level[uprio])
+		rq->prio_level[uprio] = MAX_RT_PRIO;
 	/*
 	 * Only priorities equal to the prio_level and above for their
 	 * static_prio are acceptable, and only if it's not better than
@@ -736,11 +740,8 @@ static inline int next_entitled_slot(str
 
 static void queue_expired(struct task_struct *p, struct rq *rq)
 {
-	p->array = rq->expired;
-	task_new_array(p, rq);
+	task_new_array(p, rq, rq->expired);
 	p->prio = p->normal_prio = first_prio_slot(p);
-	p->time_slice = p->quota;
-	p->rotation = rq->prio_rotation;
 }
 
 #ifdef CONFIG_SMP
@@ -800,9 +801,9 @@ static void recalc_task_prio(struct task
 			queue_expired(p, rq);
 			return;
 		} else
-			task_new_array(p, rq);
+			task_new_array(p, rq, array);
 	} else
-		task_new_array(p, rq);
+		task_new_array(p, rq, array);
 
 	queue_prio = next_entitled_slot(p, rq);
 	if (queue_prio >= MAX_PRIO) {
@@ -3445,7 +3446,7 @@ EXPORT_SYMBOL(sub_preempt_count);
 
 static inline void reset_prio_levels(struct rq *rq)
 {
-	memset(rq->prio_level, MAX_RT_PRIO, ARRAY_SIZE(rq->prio_level));
+	memset(rq->prio_level, 0, sizeof(int) * PRIO_RANGE);
 }
 
 /*

-- 
-ck