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@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dedekind1@gmail.com
Cc: juri.lelli@arm.com
Cc: mgorman@suse.de
Cc: riel@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20150515154833.667516139@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 740f90b..9917c96 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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,