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authorKirill Tkhai <tkhai@yandex.ru>2013-11-27 19:59:13 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-08 09:42:11 -0800
commit3f8878956c833443d6c6e498e9ed6a18ee30e0f5 (patch)
tree4d82b3f085f1085301ebee2c9415ff13c09af66b
parenta1192c0e5d037def6763f3873d3340615c241fe7 (diff)
downloadlinux-linaro-stable-3f8878956c833443d6c6e498e9ed6a18ee30e0f5.tar.gz
sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
commit 757dfcaa41844595964f1220f1d33182dae49976 upstream. This patch touches the RT group scheduling case. Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority, while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because changing of priority on a child level does not guarantee that the priority is the highest all over the rq. So, this leak makes RT balancing unusable. The short example: the task having the highest priority among all rq's RT tasks (no one other task has the same priority) are waking on a throttle rt_rq. The rq's cpupri is set to the task's priority equivalent, but real rq->rt.highest_prio.curr is less. The patch below fixes the problem. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> CC: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/49231385567953@web4m.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/sched/rt.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index ead0336007be..580d05b1784d 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -942,6 +942,13 @@ inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
struct rq *rq = rq_of_rt_rq(rt_rq);
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * Change rq's cpupri only if rt_rq is the top queue.
+ */
+ if (&rq->rt != rt_rq)
+ return;
+#endif
if (rq->online && prio < prev_prio)
cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
}
@@ -951,6 +958,13 @@ dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
{
struct rq *rq = rq_of_rt_rq(rt_rq);
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * Change rq's cpupri only if rt_rq is the top queue.
+ */
+ if (&rq->rt != rt_rq)
+ return;
+#endif
if (rq->online && rt_rq->highest_prio.curr != prev_prio)
cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
}