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Subject[PATCH] sched: fix rt-bandwidth hotplug race
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Subject: sched: fix rt-bandwidth hotplug race
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu Aug 14 15:42:44 CEST 2008

When we hot-unplug a cpu and rebuild the sched-domain, all cpus will be
detatched. Alex observed the case where a runqueue was stealing bandwidth
from an already disabled runqueue to satisfy its own needs.

Stop this by skipping over already disabled runqueues.

Reported-by: Alex Nixon <alex.nixon@citrix.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Alex Nixon <alex.nixon@citrix.com>
---
kernel/sched_rt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/kernel/sched_rt.c
===================================================================
--- linux-2.6.orig/kernel/sched_rt.c
+++ linux-2.6/kernel/sched_rt.c
@@ -298,7 +298,7 @@ static void __disable_runtime(struct rq
struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
s64 diff;

- if (iter == rt_rq)
+ if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
continue;

spin_lock(&iter->rt_runtime_lock);



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