From 7f9672079f5db72ba078f0e7cd1772b795ac0312 Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Sat, 22 Oct 2016 09:33:49 +1100
Subject: [PATCH 85/89] Resched when needed after calling do_set_cpus_allowed
 from outside the scheduler code, consolidating smp_send_reschedule to only be
 called if the remote CPU is online.

---
 kernel/sched/MuQSS.c | 65 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 42 insertions(+), 23 deletions(-)

diff --git a/kernel/sched/MuQSS.c b/kernel/sched/MuQSS.c
index 7fb2052..a921794 100644
--- a/kernel/sched/MuQSS.c
+++ b/kernel/sched/MuQSS.c
@@ -676,6 +676,12 @@ static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
 	next->on_cpu = 1;
 }
 
+static inline void smp_sched_reschedule(int cpu)
+{
+	if (likely(cpu_online(cpu)))
+		smp_send_reschedule(cpu);
+}
+
 /*
  * resched_task - mark a task 'to be rescheduled now'.
  *
@@ -702,7 +708,7 @@ void resched_task(struct task_struct *p)
 	}
 
 	if (set_nr_and_not_polling(p))
-		smp_send_reschedule(cpu);
+		smp_sched_reschedule(cpu);
 	else
 		trace_sched_wake_idle_without_ipi(cpu);
 }
@@ -1113,7 +1119,7 @@ static void resched_curr(struct rq *rq)
 	}
 
 	if (set_nr_and_not_polling(rq->curr))
-		smp_send_reschedule(cpu);
+		smp_sched_reschedule(cpu);
 	else
 		trace_sched_wake_idle_without_ipi(cpu);
 }
@@ -1208,7 +1214,7 @@ static inline void resched_idle(struct rq *rq)
 		return;
 	}
 
-	smp_send_reschedule(rq->cpu);
+	smp_sched_reschedule(rq->cpu);
 }
 
 static struct rq *resched_best_idle(struct task_struct *p, int cpu)
@@ -1588,7 +1594,7 @@ void kick_process(struct task_struct *p)
 	preempt_disable();
 	cpu = task_cpu(p);
 	if ((cpu != smp_processor_id()) && task_curr(p))
-		smp_send_reschedule(cpu);
+		smp_sched_reschedule(cpu);
 	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(kick_process);
@@ -1844,7 +1850,7 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
 
 	if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
 		if (!set_nr_if_polling(rq->idle))
-			smp_send_reschedule(cpu);
+			smp_sched_reschedule(cpu);
 		else
 			trace_sched_wake_idle_without_ipi(cpu);
 	}
@@ -1865,7 +1871,7 @@ void wake_up_if_idle(int cpu)
 	} else {
 		rq_lock_irqsave(rq, &flags);
 		if (likely(is_idle_task(rq->curr)))
-			smp_send_reschedule(cpu);
+			smp_sched_reschedule(cpu);
 		/* Else cpu is not in idle, do nothing here */
 		rq_unlock_irqrestore(rq, &flags);
 	}
@@ -3812,13 +3818,9 @@ static void check_smt_siblings(struct rq *this_rq)
 		rq = cpu_rq(other_cpu);
 		if (rq_idle(rq))
 			continue;
-		if (unlikely(!rq->online))
-			continue;
 		p = rq->curr;
-		if (!smt_schedule(p, this_rq)) {
-			set_tsk_need_resched(p);
-			smp_send_reschedule(other_cpu);
-		}
+		if (!smt_schedule(p, this_rq))
+			resched_curr(rq);
 	}
 }
 
@@ -3830,14 +3832,8 @@ static void wake_smt_siblings(struct rq *this_rq)
 		struct rq *rq;
 
 		rq = cpu_rq(other_cpu);
-		if (unlikely(!rq->online))
-			continue;
-		if (rq_idle(rq)) {
-			struct task_struct *p = rq->curr;
-
-			set_tsk_need_resched(p);
-			smp_send_reschedule(other_cpu);
-		}
+		if (rq_idle(rq))
+			resched_idle(rq);
 	}
 }
 #else
@@ -5578,7 +5574,7 @@ void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_ma
 	p->nr_cpus_allowed = cpumask_weight(new_mask);
 }
 
-void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+static void __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
 {
 	struct rq *rq = task_rq(p);
 
@@ -5593,6 +5589,29 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
 		 */
 		lockdep_assert_held(&rq->lock);
 	}
+}
+
+/*
+ * Calling do_set_cpus_allowed from outside the scheduler code may make the
+ * task not be able to run on its current CPU so we resched it here.
+ */
+void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+{
+	__do_set_cpus_allowed(p, new_mask);
+	if (needs_other_cpu(p, task_cpu(p))) {
+		set_task_cpu(p, valid_task_cpu(p));
+		resched_task(p);
+	}
+}
+
+/*
+ * For internal scheduler calls to do_set_cpus_allowed which will resched
+ * themselves if needed.
+ */
+static void _do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+{
+	__do_set_cpus_allowed(p, new_mask);
+	/* __set_cpus_allowed_ptr will handle the reschedule in this variant */
 	if (needs_other_cpu(p, task_cpu(p)))
 		set_task_cpu(p, valid_task_cpu(p));
 }
@@ -5790,7 +5809,7 @@ void wake_up_idle_cpu(int cpu)
 		return;
 
 	if (set_nr_and_not_polling(cpu_rq(cpu)->idle))
-		smp_send_reschedule(cpu);
+		smp_sched_reschedule(cpu);
 	else
 		trace_sched_wake_idle_without_ipi(cpu);
 }
@@ -5850,7 +5869,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 
 	queued = task_queued(p);
 
-	do_set_cpus_allowed(p, new_mask);
+	_do_set_cpus_allowed(p, new_mask);
 
 	if (p->flags & PF_KTHREAD) {
 		/*
-- 
2.7.4