sched,rt: Remove return value from pull_rt_task()

commit 8046d6806247088de5725eaf8a2580b29e50ac5a upstream.

In order to be able to use pull_rt_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/20150611124742.679002000@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[Conflicts: kernel/sched/rt.c]
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
[bwh: Backported to 3.16: use resched_task() instead of resched_curr()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 919319b5db2f9707d23dc9c643be7cb7d03a2895..ad2dcfdeec92bca9b94e9ec663e3e1fe96bb2b88 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -244,7 +244,7 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
 
 #ifdef CONFIG_SMP
 
-static int pull_rt_task(struct rq *this_rq);
+static void pull_rt_task(struct rq *this_rq);
 
 static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
 {
@@ -399,9 +399,8 @@ static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
        return false;
 }
 
-static inline int pull_rt_task(struct rq *this_rq)
+static inline void pull_rt_task(struct rq *this_rq)
 {
-       return 0;
 }
 
 static inline void queue_push_tasks(struct rq *rq)
@@ -1772,14 +1771,15 @@ static void push_rt_tasks(struct rq *rq)
                ;
 }
 
-static int pull_rt_task(struct rq *this_rq)
+static void pull_rt_task(struct rq *this_rq)
 {
-       int this_cpu = this_rq->cpu, ret = 0, cpu;
+       int this_cpu = this_rq->cpu, cpu;
+       bool resched = false;
        struct task_struct *p;
        struct rq *src_rq;
 
        if (likely(!rt_overloaded(this_rq)))
-               return 0;
+               return;
 
        /*
         * Match the barrier from rt_set_overloaded; this guarantees that if we
@@ -1836,7 +1836,7 @@ static int pull_rt_task(struct rq *this_rq)
                        if (p->prio < src_rq->curr->prio)
                                goto skip;
 
-                       ret = 1;
+                       resched = true;
 
                        deactivate_task(src_rq, p, 0);
                        set_task_cpu(p, this_cpu);
@@ -1852,7 +1852,8 @@ skip:
                double_unlock_balance(this_rq, src_rq);
        }
 
-       return ret;
+       if (resched)
+               resched_task(this_rq->curr);
 }
 
 /*
@@ -1948,8 +1949,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
        if (!p->on_rq || rq->rt.rt_nr_running)
                return;
 
-       if (pull_rt_task(rq))
-               resched_task(rq->curr);
+       pull_rt_task(rq);
 }
 
 void __init init_sched_rt_class(void)