[ 3.5.y.z extended stable ] Patch "sched/rt: Use root_domain of rt_rq not current processor" has been added to staging queue

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Tue Feb 12 21:17:29 UTC 2013

This is a note to let you know that I have just added a patch titled

    sched/rt: Use root_domain of rt_rq not current processor

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From 19be79ad04de970ea0ec2f1cb2693dac0e607b2d Mon Sep 17 00:00:00 2001
From: Shawn Bohrer <sbohrer at rgmadvisors.com>
Date: Mon, 14 Jan 2013 11:55:31 -0600
Subject: [PATCH] sched/rt: Use root_domain of rt_rq not current processor

commit aa7f67304d1a03180f463258aa6f15a8b434e77d upstream.

When the system has multiple domains do_sched_rt_period_timer()
can run on any CPU and may iterate over all rt_rq in
cpu_online_mask.  This means when balance_runtime() is run for a
given rt_rq that rt_rq may be in a different rd than the current
processor.  Thus if we use smp_processor_id() to get rd in
do_balance_runtime() we may borrow runtime from a rt_rq that is
not part of our rd.

This changes do_balance_runtime to get the rd from the passed in
rt_rq ensuring that we borrow runtime only from the correct rd
for the given rt_rq.

This fixes a BUG at kernel/sched/rt.c:687! in __disable_runtime
when we try reclaim runtime lent to other rt_rq but runtime has
been lent to a rt_rq in another rd.

Signed-off-by: Shawn Bohrer <sbohrer at rgmadvisors.com>
Acked-by: Steven Rostedt <rostedt at goodmis.org>
Acked-by: Mike Galbraith <bitbucket at online.de>
Cc: peterz at infradead.org
Link: http://lkml.kernel.org/r/1358186131-29494-1-git-send-email-sbohrer@rgmadvisors.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 kernel/sched/rt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 573e1ca..2a05e56 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -566,7 +566,7 @@ static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 static int do_balance_runtime(struct rt_rq *rt_rq)
 	struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
-	struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
+	struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
 	int i, weight, more = 0;
 	u64 rt_period;


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