Patch "sched,dl: Remove return value from pull_dl_task()" has been added to the 3.14-stable tree

Patch "sched,dl: Remove return value from pull_dl_task()" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    sched,dl: Remove return value from pull_dl_task()

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sched-dl-remove-return-value-from-pull_dl_task.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 0ea60c2054fc3b0c3eb68ac4f6884f3ee78d9925 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 11 Jun 2015 14:46:42 +0200
Subject: sched,dl: Remove return value from pull_dl_task()

From: Peter Zijlstra <peterz@infradead.org>

commit 0ea60c2054fc3b0c3eb68ac4f6884f3ee78d9925 upstream.

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@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124742.859398977@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- 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_
 					   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)


Patches currently in stable-queue which might be from peterz@infradead.org are

queue-3.14/sched-rt-remove-return-value-from-pull_rt_task.patch
queue-3.14/sched-replace-post_schedule-with-a-balance-callback-list.patch
queue-3.14/sched-clean-up-idle-task-smp-logic.patch
queue-3.14/sched-dl-convert-switched_-from-to-_dl-prio_changed_dl-to-balance-callbacks.patch
queue-3.14/sched-dl-remove-return-value-from-pull_dl_task.patch
queue-3.14/sched-allow-balance-callbacks-for-check_class_changed.patch
queue-3.14/sched-rt-convert-switched_-from-to-_rt-prio_changed_rt-to-balance-callbacks.patch