1 files changed, 44 insertions, 0 deletions
diff --git a/debian/patches-rt/sched-core-migrate_enable-must-access-takedown_cpu_t.patch b/debian/patches-rt/sched-core-migrate_enable-must-access-takedown_cpu_t.patch
new file mode 100644
index 000000000..384a89080
--- /dev/null
+++ b/debian/patches-rt/sched-core-migrate_enable-must-access-takedown_cpu_t.patch
@@ -0,0 +1,44 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Fri, 29 Nov 2019 17:24:55 +0100
+Subject: [PATCH] sched/core: migrate_enable() must access takedown_cpu_task on
+ !HOTPLUG_CPU
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz
+
+The variable takedown_cpu_task is never declared/used on !HOTPLUG_CPU
+except for migrate_enable(). This leads to a link error.
+
+Don't use takedown_cpu_task in !HOTPLUG_CPU.
+
+Reported-by: Dick Hollenbeck <dick@softplc.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/cpu.c        |    2 ++
+ kernel/sched/core.c |    2 ++
+ 2 files changed, 4 insertions(+)
+
+--- a/kernel/cpu.c
++++ b/kernel/cpu.c
+@@ -887,7 +887,9 @@ static int take_cpu_down(void *_param)
+ 	return 0;
+ }
+ 
++#ifdef CONFIG_PREEMPT_RT
+ struct task_struct *takedown_cpu_task;
++#endif
+ 
+ static int takedown_cpu(unsigned int cpu)
+ {
+--- a/kernel/sched/core.c
++++ b/kernel/sched/core.c
+@@ -8129,9 +8129,11 @@ void migrate_enable(void)
+ 
+ 	p->migrate_disable = 0;
+ 	rq->nr_pinned--;
++#ifdef CONFIG_HOTPLUG_CPU
+ 	if (rq->nr_pinned == 0 && unlikely(!cpu_active(cpu)) &&
+ 	    takedown_cpu_task)
+ 		wake_up_process(takedown_cpu_task);
++#endif
+ 
+ 	if (!p->migrate_disable_scheduled)
+ 		goto out;