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authorJohn Blackwood <john.blackwood@ccur.com>2008-08-26 15:09:43 -0400
committerIngo Molnar <mingo@elte.hu>2008-08-28 11:13:24 +0200
commitf3ade837808121ff8bab9c56725f4fe40ec85a56 (patch)
treeeb9a8d87bff0a7d11eade583a7582e3c765e3b80
parent354879bb977e06695993435745f06a0f6d39ce2b (diff)
sched: fix sched_rt_rq_enqueue() resched idle
When sysctl_sched_rt_runtime is set to something other than -1 and the CONFIG_RT_GROUP_SCHED kernel parameter is NOT enabled, we get into a state where we see one or more CPUs idling forvever even though there are real-time tasks in their rt runqueue that are able to run (no longer throttled). The sequence is: - A real-time task is running when the timer sets the rt runqueue to throttled, and the rt task is resched_task()ed and switched out, and idle is switched in since there are no non-rt tasks to run on that cpu. - Eventually the do_sched_rt_period_timer() runs and un-throttles the rt runqueue, but we just exit the timer interrupt and go back to executing the idle task in the idle loop forever. If we change the sched_rt_rq_enqueue() routine to use some of the code from the CONFIG_RT_GROUP_SCHED enabled version of this same routine and resched_task() the currently executing task (idle in our case) if it is a lower priority task than the higher rt task in the now un-throttled runqueue, the problem is no longer observed. Signed-off-by: John Blackwood <john.blackwood@ccur.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched_rt.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 998ba54b454..07d9b330790 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -199,6 +199,8 @@ static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
+ if (rt_rq->rt_nr_running)
+ resched_task(rq_of_rt_rq(rt_rq)->curr);
}
static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)