From 5c9877d89fb1382f91ec5164c0322737bb5a9d14 Mon Sep 17 00:00:00 2001
From: Scott Wood <swood@redhat.com>
Date: Sat, 12 Oct 2019 01:52:12 -0500
Subject: [PATCH 483/518] sched: migrate_enable: Use select_fallback_rq()

[ Upstream commit adfa969d4cfcc995a9d866020124e50f1827d2d1 ]

migrate_enable() currently open-codes a variant of select_fallback_rq().
However, it does not have the "No more Mr. Nice Guy" fallback and thus
it will pass an invalid CPU to the migration thread if cpus_mask only
contains a CPU that is !active.

Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
 kernel/sched/core.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 99bf52f77fcd5..757030bf86f8e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7010,6 +7010,7 @@ void migrate_enable(void)
 	if (p->migrate_disable_update) {
 		struct rq *rq;
 		struct rq_flags rf;
+		int cpu = task_cpu(p);
 
 		rq = task_rq_lock(p, &rf);
 		update_rq_clock(rq);
@@ -7019,21 +7020,15 @@ void migrate_enable(void)
 
 		p->migrate_disable_update = 0;
 
-		WARN_ON(smp_processor_id() != task_cpu(p));
-		if (!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
-			const struct cpumask *cpu_valid_mask = cpu_active_mask;
-			struct migration_arg arg;
-			unsigned int dest_cpu;
-
-			if (p->flags & PF_KTHREAD) {
-				/*
-				 * Kernel threads are allowed on online && !active CPUs
-				 */
-				cpu_valid_mask = cpu_online_mask;
-			}
-			dest_cpu = cpumask_any_and(cpu_valid_mask, &p->cpus_mask);
-			arg.task = p;
-			arg.dest_cpu = dest_cpu;
+		WARN_ON(smp_processor_id() != cpu);
+		if (!cpumask_test_cpu(cpu, &p->cpus_mask)) {
+			struct migration_arg arg = { p };
+			struct rq_flags rf;
+
+			rq = task_rq_lock(p, &rf);
+			update_rq_clock(rq);
+			arg.dest_cpu = select_fallback_rq(cpu, p);
+			task_rq_unlock(rq, p, &rf);
 
 			unpin_current_cpu();
 			preempt_lazy_enable();
-- 
2.41.0

