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Subject[PATCH RT 19/23] sched/core: migrate_enable() must access takedown_cpu_task on !HOTPLUG_CPU
Date
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

v4.14.170-rt75-rc2 stable review patch.
If anyone has any objections, please let me know.

-----------


[ 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: Tom Zanussi <zanussi@kernel.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 17b1ed41bc06..861712ebb81d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -858,7 +858,9 @@ 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 ceddb1e27caf..e10e3956bb29 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6987,9 +6987,11 @@ 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;
--
2.14.1
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