From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 14 Aug 2008 13:49:00 +0000 (+0200)
Subject: sched: fix rt-bandwidth hotplug race
X-Git-Tag: firefly_0821_release~18239^2~1
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f1679d08480008e06fd619c71635ed33274e2595;p=firefly-linux-kernel-4.4.55.git

sched: fix rt-bandwidth hotplug race

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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 6163e4cf885b..998ba54b4543 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -298,7 +298,7 @@ static void __disable_runtime(struct rq *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);