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authorKirill Tkhai <ktkhai@parallels.com>2014-03-06 13:32:01 +0400
committerIngo Molnar <mingo@kernel.org>2014-03-11 12:05:39 +0100
commit4c6c4e38c4e9a454889298dcc498174968d14a09 (patch)
treeffb6a22c1f3a58667b3c745fe055b6dab3065443 /kernel/sched/sched.h
parente4aa358b6c23f98b2715594f6b1e9a4996a55f04 (diff)
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sched/core: Fix endless loop in pick_next_task()
1) Single cpu machine case. When rq has only RT tasks, but no one of them can be picked because of throttling, we enter in endless loop. pick_next_task_{dl,rt} return NULL. In pick_next_task_fair() we permanently go to retry if (rq->nr_running != rq->cfs.h_nr_running) return RETRY_TASK; (rq->nr_running is not being decremented when rt_rq becomes throttled). No chances to unthrottle any rt_rq or to wake fair here, because of rq is locked permanently and interrupts are disabled. 2) In case of SMP this can cause a hang too. Although we unlock rq in idle_balance(), interrupts are still disabled. The solution is to check for available tasks in DL and RT classes instead of checking for sum. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1394098321.19290.11.camel@tkhai Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/sched.h')
-rw-r--r--kernel/sched/sched.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 378bff7..f2de7a1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -423,6 +423,18 @@ struct rt_rq {
#endif
};
+#ifdef CONFIG_RT_GROUP_SCHED
+static inline int rt_rq_throttled(struct rt_rq *rt_rq)
+{
+ return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
+}
+#else
+static inline int rt_rq_throttled(struct rt_rq *rt_rq)
+{
+ return rt_rq->rt_throttled;
+}
+#endif
+
/* Deadline class' related fields in a runqueue */
struct dl_rq {
/* runqueue is an rbtree, ordered by deadline */
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