linux-kernel - [PATCH 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

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Message-Id: <1428310399-13489-7-git-send-email-wanpeng.li@linux.intel.com>
Date:	Mon,  6 Apr 2015 16:53:19 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: [PATCH 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl or stop task 
can slip in, in which case need to reschedule. This patch add the reschedule
when the scenario occurs.

Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
---
 kernel/sched/rt.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 575da76..cc973e8 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
 	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
 		return;
 
-	if (pull_rt_task(rq))
+	/*
+	 * pull_rt_task() can drop (and re-acquire) rq->lock; this
+	 * means a dl or stop task can slip in, in which case we need
+	 * to reschedule.
+	 */
+	if (pull_rt_task(rq) ||
+		(unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
+			rq->dl.dl_nr_running)))
 		resched_curr(rq);
 }
 
@@ -2197,6 +2204,16 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
 		 */
 		if (oldprio < p->prio)
 			pull_rt_task(rq);
+
+		/*
+		 * pull_rt_task() can drop (and re-acquire) rq->lock; this
+		 * means a dl or stop task can slip in, in which case we need
+		 * to reschedule.
+		 */
+		if (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
+			rq->dl.dl_nr_running))
+			resched_curr(rq);
+
 		/*
 		 * If there's a higher priority task waiting to run
 		 * then reschedule. Note, the above pull_rt_task
-- 
1.9.1

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