This is a note to let you know that I've just added the patch titled
sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled
to the 3.4-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-rt-fix-isolated-cpus-leaving-root_task_group-indefinitely-throttled.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e221d028bb08b47e624c5f0a31732c642db9d19a Mon Sep 17 00:00:00 2001
From: Mike Galbraith <efault@xxxxxx>
Date: Tue, 7 Aug 2012 10:02:38 +0200
Subject: sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled
From: Mike Galbraith <efault@xxxxxx>
commit e221d028bb08b47e624c5f0a31732c642db9d19a upstream.
Root task group bandwidth replenishment must service all CPUs, regardless of
where the timer was last started, and regardless of the isolation mechanism,
lest 'Quoth the Raven, "Nevermore"' become rt scheduling policy.
Signed-off-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1344326558.6968.25.camel@xxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/rt.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -782,6 +782,19 @@ static int do_sched_rt_period_timer(stru
const struct cpumask *span;
span = sched_rt_period_mask();
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * FIXME: isolated CPUs should really leave the root task group,
+ * whether they are isolcpus or were isolated via cpusets, lest
+ * the timer run on a CPU which does not service all runqueues,
+ * potentially leaving other CPUs indefinitely throttled. If
+ * isolation is really required, the user will turn the throttle
+ * off to kill the perturbations it causes anyway. Meanwhile,
+ * this maintains functionality for boot and/or troubleshooting.
+ */
+ if (rt_b == &root_task_group.rt_bandwidth)
+ span = cpu_online_mask;
+#endif
for_each_cpu(i, span) {
int enqueue = 0;
struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
Patches currently in stable-queue which might be from efault@xxxxxx are
queue-3.4/sched-rt-fix-isolated-cpus-leaving-root_task_group-indefinitely-throttled.patch
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