[PATCH RT 29/32] sched/core: migrate_enable() must access takedown_cpu_task on !HOTPLUG_CPU

Steven Rostedt
2020-01-17T17:41:57Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

[ Upstream commit a61d1977f692e46bad99a100f264981ba08cb4bd ]

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>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/cpu.c | 2 ++
kernel/sched/core.c | 2 ++
2 files changed, 4 insertions(+)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 5366c8c69c2f..b9d7ac61d707 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -846,7 +846,9 @@ static int take_cpu_down(void *_param)
return 0;
}

+#ifdef CONFIG_PREEMPT_RT_BASE
struct task_struct *takedown_cpu_task;
+#endif

static int takedown_cpu(unsigned int cpu)
{
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e465381b464d..cbd76324babd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7314,9 +7314,11 @@ 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;
--
2.24.1