sched: Make sched_class::set_cpus_allowed() unconditional

Give every class a set_cpus_allowed() method, this enables some small optimization in the RT,DL implementation by avoiding a double cpumask_weight() call. Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
cail · Aug 12, 2015 · c5b2803 · c5b2803
1 parent 25834c7
commit c5b2803
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Showing 7 changed files with 36 additions and 18 deletions.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
@@ -1151,17 +1151,22 @@ static int migration_cpu_stop(void *data)
 	return 0;
 }
 
-void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+/*
+ * sched_class::set_cpus_allowed must do the below, but is not required to
+ * actually call this function.
+ */
+void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
 {
-	lockdep_assert_held(&p->pi_lock);
-
-	if (p->sched_class->set_cpus_allowed)
-		p->sched_class->set_cpus_allowed(p, new_mask);
-
 	cpumask_copy(&p->cpus_allowed, new_mask);
 	p->nr_cpus_allowed = cpumask_weight(new_mask);
 }
 
+void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+{
+	lockdep_assert_held(&p->pi_lock);
+	p->sched_class->set_cpus_allowed(p, new_mask);
+}
+
 /*
  * Change a given task's CPU affinity. Migrate the thread to a
  * proper CPU and schedule it away if the CPU it's executing on

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
@@ -1696,21 +1696,21 @@ static void set_cpus_allowed_dl(struct task_struct *p,
 		raw_spin_unlock(&src_dl_b->lock);
 	}
 
-	/*
-	 * 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))
-		return;
-
 	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))
-		return;
+		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
@@ -1727,6 +1727,10 @@ static void set_cpus_allowed_dl(struct task_struct *p,
 	}
 
 	update_dl_migration(&rq->dl);
+
+done:
+	cpumask_copy(&p->cpus_allowed, new_mask);
+	p->nr_cpus_allowed = weight;
 }
 
 /* Assumes rq->lock is held */

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -8252,6 +8252,7 @@ const struct sched_class fair_sched_class = {
 
 	.task_waking		= task_waking_fair,
 	.task_dead		= task_dead_fair,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.set_curr_task          = set_curr_task_fair,

diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
@@ -96,6 +96,7 @@ const struct sched_class idle_sched_class = {
 
 #ifdef CONFIG_SMP
 	.select_task_rq		= select_task_rq_idle,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.set_curr_task          = set_curr_task_idle,

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
@@ -2084,17 +2084,17 @@ static void set_cpus_allowed_rt(struct task_struct *p,
 
 	BUG_ON(!rt_task(p));
 
-	if (!task_on_rq_queued(p))
-		return;
-
 	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))
-		return;
+		goto done;
+
+	if (!task_on_rq_queued(p))
+		goto done;
 
 	rq = task_rq(p);
 
@@ -2113,6 +2113,10 @@ static void set_cpus_allowed_rt(struct task_struct *p,
 	}
 
 	update_rt_migration(&rq->rt);
+
+done:
+	cpumask_copy(&p->cpus_allowed, new_mask);
+	p->nr_cpus_allowed = weight;
 }
 
 /* Assumes rq->lock is held */

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
@@ -1255,6 +1255,8 @@ extern void trigger_load_balance(struct rq *rq);
 extern void idle_enter_fair(struct rq *this_rq);
 extern void idle_exit_fair(struct rq *this_rq);
 
+extern void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask);
+
 #else
 
 static inline void idle_enter_fair(struct rq *rq) { }

diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
@@ -123,6 +123,7 @@ const struct sched_class stop_sched_class = {
 
 #ifdef CONFIG_SMP
 	.select_task_rq		= select_task_rq_stop,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.set_curr_task          = set_curr_task_stop,