[tip:sched/core] sched: Change the sched_class::set_cpus_allowed( ) calling context

From: tip-bot for Peter Zijlstra
Date: Wed Aug 12 2015 - 08:39:39 EST

Commit-ID: 6c37067e27867db172b988cc11b9ff921175dee5
Gitweb: http://git.kernel.org/tip/6c37067e27867db172b988cc11b9ff921175dee5
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 15 May 2015 17:43:36 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 12 Aug 2015 12:06:10 +0200

sched: Change the sched_class::set_cpus_allowed() calling context

Change the calling context of sched_class::set_cpus_allowed() such
that we can assume the task is inactive.

This allows us to easily make changes that affect accounting done by
enqueue/dequeue. This does in fact completely remove
set_cpus_allowed_rt() and greatly reduces set_cpus_allowed_dl().

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dedekind1@xxxxxxxxx
Cc: juri.lelli@xxxxxxx
Cc: mgorman@xxxxxxx
Cc: riel@xxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Link: http://lkml.kernel.org/r/20150515154833.667516139@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 23 +++++++++++++++++++++++
kernel/sched/deadline.c | 39 ++-------------------------------------
kernel/sched/rt.c | 45 +--------------------------------------------
3 files changed, 26 insertions(+), 81 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 740f90b..9917c96 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1163,8 +1163,31 @@ void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_ma

void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
+ struct rq *rq = task_rq(p);
+ bool queued, running;
+
lockdep_assert_held(&p->pi_lock);
+
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+
+ if (queued) {
+ /*
+ * Because __kthread_bind() calls this on blocked tasks without
+ * holding rq->lock.
+ */
+ lockdep_assert_held(&rq->lock);
+ dequeue_task(rq, p, 0);
+ }
+ if (running)
+ put_prev_task(rq, p);
+
p->sched_class->set_cpus_allowed(p, new_mask);
+
+ if (running)
+ p->sched_class->set_curr_task(rq);
+ if (queued)
+ enqueue_task(rq, p, 0);
}

/*
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index dc357fa..b473056 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1668,9 +1668,8 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
static void set_cpus_allowed_dl(struct task_struct *p,
const struct cpumask *new_mask)
{
- struct rq *rq;
struct root_domain *src_rd;
- int weight;
+ struct rq *rq;

BUG_ON(!dl_task(p));

@@ -1696,41 +1695,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
raw_spin_unlock(&src_dl_b->lock);
}

- weight = cpumask_weight(new_mask);
-
- /*
- * Only update if the process changes its state from whether it
- * can migrate or not.
- */
- if ((p->nr_cpus_allowed > 1) == (weight > 1))
- goto done;
-
- /*
- * Update only if the task is actually running (i.e.,
- * it is on the rq AND it is not throttled).
- */
- if (!on_dl_rq(&p->dl))
- goto done;
-
- /*
- * The process used to be able to migrate OR it can now migrate
- */
- if (weight <= 1) {
- if (!task_current(rq, p))
- dequeue_pushable_dl_task(rq, p);
- BUG_ON(!rq->dl.dl_nr_migratory);
- rq->dl.dl_nr_migratory--;
- } else {
- if (!task_current(rq, p))
- enqueue_pushable_dl_task(rq, p);
- rq->dl.dl_nr_migratory++;
- }
-
- update_dl_migration(&rq->dl);
-
-done:
- cpumask_copy(&p->cpus_allowed, new_mask);
- p->nr_cpus_allowed = weight;
+ set_cpus_allowed_common(p, new_mask);
}

/* Assumes rq->lock is held */
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 63692ef..d2ea593 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2076,49 +2076,6 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
push_rt_tasks(rq);
}

-static void set_cpus_allowed_rt(struct task_struct *p,
- const struct cpumask *new_mask)
-{
- struct rq *rq;
- int weight;
-
- BUG_ON(!rt_task(p));
-
- weight = cpumask_weight(new_mask);
-
- /*
- * Only update if the process changes its state from whether it
- * can migrate or not.
- */
- if ((p->nr_cpus_allowed > 1) == (weight > 1))
- goto done;
-
- if (!task_on_rq_queued(p))
- goto done;
-
- rq = task_rq(p);
-
- /*
- * The process used to be able to migrate OR it can now migrate
- */
- if (weight <= 1) {
- if (!task_current(rq, p))
- dequeue_pushable_task(rq, p);
- BUG_ON(!rq->rt.rt_nr_migratory);
- rq->rt.rt_nr_migratory--;
- } else {
- if (!task_current(rq, p))
- enqueue_pushable_task(rq, p);
- rq->rt.rt_nr_migratory++;
- }
-
- update_rt_migration(&rq->rt);
-
-done:
- cpumask_copy(&p->cpus_allowed, new_mask);
- p->nr_cpus_allowed = weight;
-}
-
/* Assumes rq->lock is held */
static void rq_online_rt(struct rq *rq)
{
@@ -2327,7 +2284,7 @@ const struct sched_class rt_sched_class = {
#ifdef CONFIG_SMP
.select_task_rq = select_task_rq_rt,

- .set_cpus_allowed = set_cpus_allowed_rt,
+ .set_cpus_allowed = set_cpus_allowed_common,
.rq_online = rq_online_rt,
.rq_offline = rq_offline_rt,
.task_woken = task_woken_rt,
--
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