linux-kernel - [PATCH] sched_rt: Use root_domain of rt

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Date:	Mon, 14 Jan 2013 11:55:31 -0600
From:	Shawn Bohrer <sbohrer@...advisors.com>
To:	peterz@...radead.org, mingo@...e.hu
Cc:	Mike Galbraith <bitbucket@...ine.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org,
	Shawn Bohrer <sbohrer@...advisors.com>
Subject: [PATCH] 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>
---
 kernel/sched/rt.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

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;

-- 
1.7.7.6

-- 

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