[PATCH 3/3] temp hack to make tick based schedule happen

[Aaron Lu <aaron.lu@linux.alibaba.com>]

When a hyperthread is forced idle and the other hyperthread has a single
CPU intensive task running, the running task can occupy the hyperthread
for a long time with no scheduling point and starve the other
hyperthread.

Fix this temporarily by always checking if the task has exceed its
timeslice and if so, do a schedule.

Signed-off-by: Aaron Lu <ziqian.lzq@antfin.com>
---
 kernel/sched/fair.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 43babc2a12a5..730c9359e9c9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4093,6 +4093,9 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 		return;
 	}
 
+	if (cfs_rq->nr_running <= 1)
+		return;
+
 	/*
 	 * Ensure that a task that missed wakeup preemption by a
 	 * narrow margin doesn't have to wait for a full slice.
@@ -4261,8 +4264,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 		return;
 #endif
 
-	if (cfs_rq->nr_running > 1)
-		check_preempt_tick(cfs_rq, curr);
+	check_preempt_tick(cfs_rq, curr);
 }
 
 
-- 
2.19.1.3.ge56e4f7