sched/core: Provide a tsk_nr_cpus_allowed() helper

tsk_nr_cpus_allowed() is an accessor for task->nr_cpus_allowed which allows
us to change the representation of ->nr_cpus_allowed if required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1462969411-17735-2-git-send-email-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -1930,6 +1930,11 @@ extern int arch_task_struct_size __read_mostly;
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
 #define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)
 
+static inline int tsk_nr_cpus_allowed(struct task_struct *p)
+{
+	return p->nr_cpus_allowed;
+}
+
 #define TNF_MIGRATED	0x01
 #define TNF_NO_GROUP	0x02
 #define TNF_SHARED	0x04

kernel/sched/core.c

@@ -1585,7 +1585,7 @@ int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
 {
 	lockdep_assert_held(&p->pi_lock);
 
-	if (p->nr_cpus_allowed > 1)
+	if (tsk_nr_cpus_allowed(p) > 1)
 		cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
 	else
 		cpu = cpumask_any(tsk_cpus_allowed(p));

kernel/sched/deadline.c

@@ -134,7 +134,7 @@ static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
 	struct task_struct *p = dl_task_of(dl_se);
 
-	if (p->nr_cpus_allowed > 1)
+	if (tsk_nr_cpus_allowed(p) > 1)
 		dl_rq->dl_nr_migratory++;
 
 	update_dl_migration(dl_rq);
@@ -144,7 +144,7 @@ static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
 	struct task_struct *p = dl_task_of(dl_se);
 
-	if (p->nr_cpus_allowed > 1)
+	if (tsk_nr_cpus_allowed(p) > 1)
 		dl_rq->dl_nr_migratory--;
 
 	update_dl_migration(dl_rq);
@@ -966,7 +966,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 
 	enqueue_dl_entity(&p->dl, pi_se, flags);
 
-	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
+	if (!task_current(rq, p) && tsk_nr_cpus_allowed(p) > 1)
 		enqueue_pushable_dl_task(rq, p);
 }
 
@@ -1040,9 +1040,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
 	 * try to make it stay here, it might be important.
 	 */
 	if (unlikely(dl_task(curr)) &&
-	    (curr->nr_cpus_allowed < 2 ||
+	    (tsk_nr_cpus_allowed(curr) < 2 ||
 	     !dl_entity_preempt(&p->dl, &curr->dl)) &&
-	    (p->nr_cpus_allowed > 1)) {
+	    (tsk_nr_cpus_allowed(p) > 1)) {
 		int target = find_later_rq(p);
 
 		if (target != -1 &&
@@ -1063,7 +1063,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * Current can't be migrated, useless to reschedule,
 	 * let's hope p can move out.
 	 */
-	if (rq->curr->nr_cpus_allowed == 1 ||
+	if (tsk_nr_cpus_allowed(rq->curr) == 1 ||
 	    cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
 		return;
 
@@ -1071,7 +1071,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * p is migratable, so let's not schedule it and
 	 * see if it is pushed or pulled somewhere else.
 	 */
-	if (p->nr_cpus_allowed != 1 &&
+	if (tsk_nr_cpus_allowed(p) != 1 &&
 	    cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
 		return;
 
@@ -1186,7 +1186,7 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
 {
 	update_curr_dl(rq);
 
-	if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
+	if (on_dl_rq(&p->dl) && tsk_nr_cpus_allowed(p) > 1)
 		enqueue_pushable_dl_task(rq, p);
 }
 
@@ -1287,7 +1287,7 @@ static int find_later_rq(struct task_struct *task)
 	if (unlikely(!later_mask))
 		return -1;
 
-	if (task->nr_cpus_allowed == 1)
+	if (tsk_nr_cpus_allowed(task) == 1)
 		return -1;
 
 	/*
@@ -1433,7 +1433,7 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
 
 	BUG_ON(rq->cpu != task_cpu(p));
 	BUG_ON(task_current(rq, p));
-	BUG_ON(p->nr_cpus_allowed <= 1);
+	BUG_ON(tsk_nr_cpus_allowed(p) <= 1);
 
 	BUG_ON(!task_on_rq_queued(p));
 	BUG_ON(!dl_task(p));
@@ -1472,7 +1472,7 @@ retry:
 	 */
 	if (dl_task(rq->curr) &&
 	    dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
-	    rq->curr->nr_cpus_allowed > 1) {
+	    tsk_nr_cpus_allowed(rq->curr) > 1) {
 		resched_curr(rq);
 		return 0;
 	}
@@ -1619,9 +1619,9 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
 {
 	if (!task_running(rq, p) &&
 	    !test_tsk_need_resched(rq->curr) &&
-	    p->nr_cpus_allowed > 1 &&
+	    tsk_nr_cpus_allowed(p) > 1 &&
 	    dl_task(rq->curr) &&
-	    (rq->curr->nr_cpus_allowed < 2 ||
+	    (tsk_nr_cpus_allowed(rq->curr) < 2 ||
 	     !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
 		push_dl_tasks(rq);
 	}
@@ -1725,7 +1725,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 
 	if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
-		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
+		if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
 			queue_push_tasks(rq);
 #else
 		if (dl_task(rq->curr))

kernel/sched/rt.c

@@ -334,7 +334,7 @@ static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 
 	rt_rq->rt_nr_total++;
-	if (p->nr_cpus_allowed > 1)
+	if (tsk_nr_cpus_allowed(p) > 1)
 		rt_rq->rt_nr_migratory++;
 
 	update_rt_migration(rt_rq);
@@ -351,7 +351,7 @@ static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 	rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 
 	rt_rq->rt_nr_total--;
-	if (p->nr_cpus_allowed > 1)
+	if (tsk_nr_cpus_allowed(p) > 1)
 		rt_rq->rt_nr_migratory--;
 
 	update_rt_migration(rt_rq);
@@ -1324,7 +1324,7 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 
 	enqueue_rt_entity(rt_se, flags);
 
-	if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
+	if (!task_current(rq, p) && tsk_nr_cpus_allowed(p) > 1)
 		enqueue_pushable_task(rq, p);
 }
 
@@ -1413,7 +1413,7 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
 	 * will have to sort it out.
 	 */
 	if (curr && unlikely(rt_task(curr)) &&
-	    (curr->nr_cpus_allowed < 2 ||
+	    (tsk_nr_cpus_allowed(curr) < 2 ||
 	     curr->prio <= p->prio)) {
 		int target = find_lowest_rq(p);
 
@@ -1437,7 +1437,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
 	 * Current can't be migrated, useless to reschedule,
 	 * let's hope p can move out.
 	 */
-	if (rq->curr->nr_cpus_allowed == 1 ||
+	if (tsk_nr_cpus_allowed(rq->curr) == 1 ||
 	    !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
 		return;
 
@@ -1445,7 +1445,7 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
 	 * p is migratable, so let's not schedule it and
 	 * see if it is pushed or pulled somewhere else.
 	 */
-	if (p->nr_cpus_allowed != 1
+	if (tsk_nr_cpus_allowed(p) != 1
 	    && cpupri_find(&rq->rd->cpupri, p, NULL))
 		return;
 
@@ -1579,7 +1579,7 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 	 * The previous task needs to be made eligible for pushing
 	 * if it is still active
 	 */
-	if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
+	if (on_rt_rq(&p->rt) && tsk_nr_cpus_allowed(p) > 1)
 		enqueue_pushable_task(rq, p);
 }
 
@@ -1629,7 +1629,7 @@ static int find_lowest_rq(struct task_struct *task)
 	if (unlikely(!lowest_mask))
 		return -1;
 
-	if (task->nr_cpus_allowed == 1)
+	if (tsk_nr_cpus_allowed(task) == 1)
 		return -1; /* No other targets possible */
 
 	if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
@@ -1762,7 +1762,7 @@ static struct task_struct *pick_next_pushable_task(struct rq *rq)
 
 	BUG_ON(rq->cpu != task_cpu(p));
 	BUG_ON(task_current(rq, p));
-	BUG_ON(p->nr_cpus_allowed <= 1);
+	BUG_ON(tsk_nr_cpus_allowed(p) <= 1);
 
 	BUG_ON(!task_on_rq_queued(p));
 	BUG_ON(!rt_task(p));
@@ -2122,9 +2122,9 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
 {
 	if (!task_running(rq, p) &&
 	    !test_tsk_need_resched(rq->curr) &&
-	    p->nr_cpus_allowed > 1 &&
+	    tsk_nr_cpus_allowed(p) > 1 &&
 	    (dl_task(rq->curr) || rt_task(rq->curr)) &&
-	    (rq->curr->nr_cpus_allowed < 2 ||
+	    (tsk_nr_cpus_allowed(rq->curr) < 2 ||
 	     rq->curr->prio <= p->prio))
 		push_rt_tasks(rq);
 }
@@ -2197,7 +2197,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
 	 */
 	if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
-		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
+		if (tsk_nr_cpus_allowed(p) > 1 && rq->rt.overloaded)
 			queue_push_tasks(rq);
 #else
 		if (p->prio < rq->curr->prio)