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Date: Fri, 09 Jan 2009 17:29:22 -0500
From: Gregory Haskins <ghaskins@...ell.com>
To: Arnaldo Carvalho de Melo <acme@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>,
RT <linux-rt-users@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: 2.6.24.7-rt25 and 2.6.26.8-rt12
Arnaldo Carvalho de Melo wrote:
> Em Sat, Dec 20, 2008 at 12:55:20AM -0500, Steven Rostedt escreveu:
>
>> We are pleased to announce the 2.6.24.7-rt25 and 2.6.26.8-rt12 trees,
>> which can be downloaded from the location:
>>
>> http://rt.et.redhat.com/download/
>>
>> Information on the RT patch can be found at:
>>
>> http://rt.wiki.kernel.org/index.php/Main_Page
>>
>> Changes since 2.6.26.6-rt11
>>
>
> I managed to boot 2.6.26.8-rt12 once, but it oopsed when I started a
> market data workload while generating load with a make -j 64 kernel
> compile, couldn't get the proper backtrace because I was swamped with
> /proc/sys/kernel/hung_task_timeout_secs related messages.
Hi Arnaldo,
I believe this may have been a result of the patch:
sched-prioritize-non-migrating-rt-tasks.patch
Please try this patch:
----------------------
commit a8841359ef48279dd3c11f0dca614d7f9da6f7b7
Author: Gregory Haskins <ghaskins@...ell.com>
Date: Fri Jan 9 17:27:43 2009 -0500
sched: revert "sched-prioritize-non-migrating-rt-tasks.patch"
This patch was originally accepted to -rt and later pulled upstream
to -tip. However, it was later dropped due to a better alternative
solutuion. Therefore, we dropped this patch in 28-rt but inadvertently
left it in 26-rt. Now it seems to be causing a crash in 26.8-rt12.
However, it is not worth finding/fixing the problem. We should just
drop the patch in 26-rt as well.
For the convenience of testers out there, please apply this patch to
-rt12 to revert the logic. The proper solution for -rt13 is to just
remove sched-prioritize-non-migrating-rt-tasks.patch from the series
file.
Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
diff --git a/kernel/sched.c b/kernel/sched.c
index c56bfde..88c9519 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -203,8 +203,7 @@ static inline int task_has_rt_policy(struct
task_struct *p)
*/
struct rt_prio_array {
DECLARE_BITMAP(bitmap, MAX_RT_PRIO+1); /* include 1 bit for
delimiter */
- struct list_head xqueue[MAX_RT_PRIO]; /* exclusive queue */
- struct list_head squeue[MAX_RT_PRIO]; /* shared queue */
+ struct list_head queue[MAX_RT_PRIO];
};
struct rt_bandwidth {
@@ -8360,8 +8359,7 @@ static void init_rt_rq(struct rt_rq *rt_rq, struct
rq *rq)
array = &rt_rq->active;
for (i = 0; i < MAX_RT_PRIO; i++) {
- INIT_LIST_HEAD(array->xqueue + i);
- INIT_LIST_HEAD(array->squeue + i);
+ INIT_LIST_HEAD(array->queue + i);
__clear_bit(i, array->bitmap);
}
/* delimiter for bitsearch: */
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 4eec7aa..3b92165 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -519,13 +519,7 @@ static void __enqueue_rt_entity(struct
sched_rt_entity *rt_se)
if (group_rq && (rt_rq_throttled(group_rq) ||
!group_rq->rt_nr_running))
return;
- if (rt_se->nr_cpus_allowed == 1)
- list_add_tail(&rt_se->run_list,
- array->xqueue + rt_se_prio(rt_se));
- else
- list_add_tail(&rt_se->run_list,
- array->squeue + rt_se_prio(rt_se));
-
+ list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
__set_bit(rt_se_prio(rt_se), array->bitmap);
inc_rt_tasks(rt_se, rt_rq);
@@ -537,8 +531,7 @@ static void __dequeue_rt_entity(struct
sched_rt_entity *rt_se)
struct rt_prio_array *array = &rt_rq->active;
list_del_init(&rt_se->run_list);
- if (list_empty(array->squeue + rt_se_prio(rt_se))
- && list_empty(array->xqueue + rt_se_prio(rt_se)))
+ if (list_empty(array->queue + rt_se_prio(rt_se)))
__clear_bit(rt_se_prio(rt_se), array->bitmap);
dec_rt_tasks(rt_se, rt_rq);
@@ -667,21 +660,15 @@ static void dequeue_task_rt(struct rq *rq, struct
task_struct *p, int sleep)
/*
* Put task to the end of the run list without the overhead of dequeue
* followed by enqueue.
- *
- * Note: We always enqueue the task to the shared-queue, regardless of its
- * previous position w.r.t. exclusive vs shared. This is so that
exclusive RR
- * tasks fairly round-robin with all tasks on the runqueue, not just other
- * exclusive tasks.
*/
static
void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
{
struct rt_prio_array *array = &rt_rq->active;
+ struct list_head *queue = array->queue + rt_se_prio(rt_se);
- if (on_rt_rq(rt_se)) {
- list_del_init(&rt_se->run_list);
- list_add_tail(&rt_se->run_list, array->squeue + rt_se_prio(rt_se));
- }
+ if (on_rt_rq(rt_se))
+ list_move_tail(&rt_se->run_list, queue);
}
static void requeue_task_rt(struct rq *rq, struct task_struct *p)
@@ -739,46 +726,13 @@ static int select_task_rq_rt(struct task_struct
*p, int sync)
}
#endif /* CONFIG_SMP */
-static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
- struct rt_rq *rt_rq);
-
/*
* Preempt the current task with a newly woken task if needed:
*/
static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
{
- if (p->prio < rq->curr->prio) {
+ if (p->prio < rq->curr->prio)
resched_task(rq->curr);
- return;
- }
-
-#ifdef CONFIG_SMP
- /*
- * If:
- *
- * - the newly woken task is of equal priority to the current task
- * - the newly woken task is non-migratable while current is migratable
- * - current will be preempted on the next reschedule
- *
- * we should check to see if current can readily move to a different
- * cpu. If so, we will reschedule to allow the push logic to try
- * to move current somewhere else, making room for our non-migratable
- * task.
- */
- if((p->prio == rq->curr->prio)
- && p->rt.nr_cpus_allowed == 1
- && rq->curr->rt.nr_cpus_allowed != 1
- && pick_next_rt_entity(rq, &rq->rt) != &rq->curr->rt) {
- cpumask_t mask;
-
- if (cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
- /*
- * There appears to be other cpus that can accept
- * current, so lets reschedule to try and push it away
- */
- resched_task(rq->curr);
- }
-#endif
}
static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
@@ -792,15 +746,8 @@ static struct sched_rt_entity
*pick_next_rt_entity(struct rq *rq,
idx = sched_find_first_bit(array->bitmap);
BUG_ON(idx >= MAX_RT_PRIO);
- queue = array->xqueue + idx;
- if (!list_empty(queue))
- next = list_entry(queue->next, struct sched_rt_entity,
- run_list);
- else {
- queue = array->squeue + idx;
- next = list_entry(queue->next, struct sched_rt_entity,
- run_list);
- }
+ queue = array->queue + idx;
+ next = list_entry(queue->next, struct sched_rt_entity, run_list);
return next;
}
@@ -889,7 +836,7 @@ static struct task_struct
*pick_next_highest_task_rt(struct rq *rq, int cpu)
continue;
if (next && next->prio < idx)
continue;
- list_for_each_entry(rt_se, array->squeue + idx, run_list) {
+ list_for_each_entry(rt_se, array->queue + idx, run_list) {
struct task_struct *p = rt_task_of(rt_se);
if (pick_rt_task(rq, p, cpu)) {
next = p;
@@ -1331,14 +1278,6 @@ static void set_cpus_allowed_rt(struct
task_struct *p,
}
update_rt_migration(rq);
-
- if (unlikely(weight == 1 || p->rt.nr_cpus_allowed == 1))
- /*
- * If either the new or old weight is a "1", we need
- * to requeue to properly move between shared and
- * exclusive queues.
- */
- requeue_task_rt(rq, p);
}
p->cpus_allowed = *new_mask;
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