linux-kernel - [tip:sched/urgent] sched/rt: Use root_domain of rt

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Date:	Thu, 24 Jan 2013 12:33:10 -0800
From:	tip-bot for Shawn Bohrer <sbohrer@...advisors.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	bitbucket@...ine.de, sbohrer@...advisors.com, rostedt@...dmis.org,
	stable@...nel.org, tglx@...utronix.de
Subject: [tip:sched/urgent] sched/rt:
  Use root_domain of rt_rq not current processor

Commit-ID:  df42ae62b3a0bd1a04b68f467a84150af6274a09
Gitweb:     http://git.kernel.org/tip/df42ae62b3a0bd1a04b68f467a84150af6274a09
Author:     Shawn Bohrer <sbohrer@...advisors.com>
AuthorDate: Mon, 14 Jan 2013 11:55:31 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 24 Jan 2013 16:37:57 +0100

sched/rt: Use root_domain of rt_rq not current processor

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@...advisors.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Acked-by: Mike Galbraith <bitbucket@...ine.de>
Cc: peterz@...radead.org
Cc: <stable@...nel.org>
Link: http://lkml.kernel.org/r/1358186131-29494-1-git-send-email-sbohrer@rgmadvisors.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 418feb0..4f02b28 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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