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authorColin Cross <ccross@android.com>2012-05-16 21:34:23 -0700
committerIngo Molnar <mingo@kernel.org>2012-05-30 14:02:25 +0200
commit454c79999f7eaedcdf4c15c449e43902980cbdf5 (patch)
tree0da7f5fe6328283a2bf36648bc04e74028d5bfd8 /kernel/sched
parent29baa7478ba47d746e3625c91d3b2afbf46b4312 (diff)
downloadlinux-454c79999f7eaedcdf4c15c449e43902980cbdf5.tar.bz2
sched/rt: Fix SCHED_RR across cgroups
task_tick_rt() has an optimization to only reschedule SCHED_RR tasks if they were the only element on their rq. However, with cgroups a SCHED_RR task could be the only element on its per-cgroup rq but still be competing with other SCHED_RR tasks in its parent's cgroup. In this case, the SCHED_RR task in the child cgroup would never yield at the end of its timeslice. If the child cgroup rt_runtime_us was the same as the parent cgroup rt_runtime_us, the task in the parent cgroup would starve completely. Modify task_tick_rt() to check that the task is the only task on its rq, and that the each of the scheduling entities of its ancestors is also the only entity on its rq. Signed-off-by: Colin Cross <ccross@android.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1337229266-15798-1-git-send-email-ccross@android.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/rt.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 295da737b6fe..2a4e8dffbd6b 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1985,6 +1985,8 @@ static void watchdog(struct rq *rq, struct task_struct *p)
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
{
+ struct sched_rt_entity *rt_se = &p->rt;
+
update_curr_rt(rq);
watchdog(rq, p);
@@ -2002,12 +2004,15 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
p->rt.time_slice = RR_TIMESLICE;
/*
- * Requeue to the end of queue if we are not the only element
- * on the queue:
+ * Requeue to the end of queue if we (and all of our ancestors) are the
+ * only element on the queue
*/
- if (p->rt.run_list.prev != p->rt.run_list.next) {
- requeue_task_rt(rq, p, 0);
- set_tsk_need_resched(p);
+ for_each_sched_rt_entity(rt_se) {
+ if (rt_se->run_list.prev != rt_se->run_list.next) {
+ requeue_task_rt(rq, p, 0);
+ set_tsk_need_resched(p);
+ return;
+ }
}
}