This is a note to let you know that I've just added the patch titled
sched: Fix sched rt group scheduling when hierachy is enabled
to the 2.6.37-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fix-sched-rt-group-scheduling-when-hierachy-is-enabled.patch
and it can be found in the queue-2.6.37 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 0c3b9168017cbad2c4af3dd65ec93fe646eeaa62 Mon Sep 17 00:00:00 2001
From: Balbir Singh <[email protected]>
Date: Thu, 3 Mar 2011 17:04:35 +0530
Subject: sched: Fix sched rt group scheduling when hierachy is enabled
From: Balbir Singh <[email protected]>
commit 0c3b9168017cbad2c4af3dd65ec93fe646eeaa62 upstream.
The current sched rt code is broken when it comes to hierarchical
scheduling, this patch fixes two problems
1. It adds redundant enqueuing (harmless) when it finds a queue
has tasks enqueued, but it has no run time and it is not
throttled.
2. The most important change is in sched_rt_rq_enqueue/dequeue.
The code just picks the rt_rq belonging to the current cpu
on which the period timer runs, the patch fixes it, so that
the correct rt_se is enqueued/dequeued.
Tested with a simple hierarchy
/c/d, c and d assigned similar runtimes of 50,000 and a while
1 loop runs within "d". Both c and d get throttled, without
the patch, the task just stops running and never runs (depends
on where the sched_rt b/w timer runs). With the patch, the
task is throttled and runs as expected.
[ bharata, suggestions on how to pick the rt_se belong to the
rt_rq and correct cpu ]
Signed-off-by: Balbir Singh <[email protected]>
Acked-by: Bharata B Rao <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched_rt.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -199,11 +199,12 @@ static void dequeue_rt_entity(struct sch
static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
- int this_cpu = smp_processor_id();
struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
struct sched_rt_entity *rt_se;
- rt_se = rt_rq->tg->rt_se[this_cpu];
+ int cpu = cpu_of(rq_of_rt_rq(rt_rq));
+
+ rt_se = rt_rq->tg->rt_se[cpu];
if (rt_rq->rt_nr_running) {
if (rt_se && !on_rt_rq(rt_se))
@@ -215,10 +216,10 @@ static void sched_rt_rq_enqueue(struct r
static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
{
- int this_cpu = smp_processor_id();
struct sched_rt_entity *rt_se;
+ int cpu = cpu_of(rq_of_rt_rq(rt_rq));
- rt_se = rt_rq->tg->rt_se[this_cpu];
+ rt_se = rt_rq->tg->rt_se[cpu];
if (rt_se && on_rt_rq(rt_se))
dequeue_rt_entity(rt_se);
@@ -546,8 +547,11 @@ static int do_sched_rt_period_timer(stru
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;
raw_spin_unlock(&rt_rq->rt_runtime_lock);
- } else if (rt_rq->rt_nr_running)
+ } else if (rt_rq->rt_nr_running) {
idle = 0;
+ if (!rt_rq_throttled(rt_rq))
+ enqueue = 1;
+ }
if (enqueue)
sched_rt_rq_enqueue(rt_rq);
Patches currently in stable-queue which might be from [email protected]
are
queue-2.6.37/sched-fix-sched-rt-group-scheduling-when-hierachy-is-enabled.patch
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