linux-kernel - [PATCH for v3.14.58 6/7] sched,dl: Remove return value from pull_dl

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Message-Id: <1451985388-19492-6-git-send-email-byungchul.park@lge.com>
Date:	Tue,  5 Jan 2016 18:16:27 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	stable@...r.kernel.org
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org,
	ktkhai@...allels.com, rostedt@...dmis.org, juri.lelli@...il.com,
	pang.xunlei@...aro.org, oleg@...hat.com,
	wanpeng.li@...ux.intel.com, umgwanakikbuti@...il.com,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH for v3.14.58 6/7] sched,dl: Remove return value from pull_dl_task()

From: Peter Zijlstra <peterz@...radead.org>

In order to be able to use pull_dl_task() from a callback, we need to
do away with the return value.

Since the return value indicates if we should reschedule, do this
inside the function. Since not all callers currently do this, this can
increase the number of reschedules due rt balancing.

Too many reschedules is not a correctness issues, too few are.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: ktkhai@...allels.com
Cc: rostedt@...dmis.org
Cc: juri.lelli@...il.com
Cc: pang.xunlei@...aro.org
Cc: oleg@...hat.com
Cc: wanpeng.li@...ux.intel.com
Cc: umgwanakikbuti@...il.com
Link: http://lkml.kernel.org/r/20150611124742.859398977@infradead.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Byungchul Park <byungchul.park@....com>

Conflicts:
	kernel/sched/deadline.c
---
 kernel/sched/deadline.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index aaefe1b..ec1f21d 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1351,15 +1351,16 @@ static void push_dl_tasks(struct rq *rq)
 		;
 }
 
-static int pull_dl_task(struct rq *this_rq)
+static void pull_dl_task(struct rq *this_rq)
 {
-	int this_cpu = this_rq->cpu, ret = 0, cpu;
+	int this_cpu = this_rq->cpu, cpu;
 	struct task_struct *p;
+	bool resched = false;
 	struct rq *src_rq;
 	u64 dmin = LONG_MAX;
 
 	if (likely(!dl_overloaded(this_rq)))
-		return 0;
+		return;
 
 	/*
 	 * Match the barrier from dl_set_overloaded; this guarantees that if we
@@ -1414,7 +1415,7 @@ static int pull_dl_task(struct rq *this_rq)
 					   src_rq->curr->dl.deadline))
 				goto skip;
 
-			ret = 1;
+			resched = true;
 
 			deactivate_task(src_rq, p, 0);
 			set_task_cpu(p, this_cpu);
@@ -1427,7 +1428,8 @@ skip:
 		double_unlock_balance(this_rq, src_rq);
 	}
 
-	return ret;
+	if (resched)
+		resched_task(this_rq->curr);
 }
 
 static void pre_schedule_dl(struct rq *rq, struct task_struct *prev)
-- 
1.9.1

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