[PATCH 07/81] sched/rt: Use root_domain of rt_rq not current processor

From: Herton Ronaldo Krzesinski
Date: Tue Feb 19 2013 - 14:16:43 EST -stable review patch. If anyone has any objections, please let me know.


From: Shawn Bohrer <sbohrer@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Acked-by: Mike Galbraith <bitbucket@xxxxxxxxx>
Cc: peterz@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1358186131-29494-1-git-send-email-sbohrer@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@xxxxxxxxxxxxx>
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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