[PATCH 04/18] sched,rt: Remove return value from pull_rt_task()

Peter Zijlstra
2015-06-11T12:55:05Z

[-- Attachment #1: peterz-sched-post_schedule-2.patch --]
[-- Type: text/plain, Size: 2408 bytes --]

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>
---
kernel/sched/rt.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -260,7 +260,7 @@ int alloc_rt_sched_group(struct task_gro

#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)
{
@@ -415,9 +415,8 @@ static inline bool need_pull_rt_task(str
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)
@@ -1955,14 +1954,15 @@ static void push_irq_work_func(struct ir
}
#endif /* HAVE_RT_PUSH_IPI */

-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
@@ -1973,7 +1973,7 @@ static int pull_rt_task(struct rq *this_
#ifdef HAVE_RT_PUSH_IPI
if (sched_feat(RT_PUSH_IPI)) {
tell_cpu_to_push(this_rq);
- return 0;
+ return;
}
#endif

@@ -2026,7 +2026,7 @@ static int pull_rt_task(struct rq *this_
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);
@@ -2042,7 +2042,8 @@ static int pull_rt_task(struct rq *this_
double_unlock_balance(this_rq, src_rq);
}

- return ret;
+ if (resched)
+ resched_curr(this_rq);
}

/*
@@ -2138,8 +2139,7 @@ static void switched_from_rt(struct rq *
if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
return;

- if (pull_rt_task(rq))
- resched_curr(rq);
+ pull_rt_task(rq);
}

void __init init_sched_rt_class(void)