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From: Mike Galbraith <efault@gmx.de>
Date: Sun, 19 Aug 2018 08:28:35 +0200
Subject: [PATCH 228/342] sched: Allow pinned user tasks to be awakened to the
CPU they pinned
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=1a7a03ac5f6eb866ddd317630b747d6e8f81013b
Since commit 7af443ee16976 ("sched/core: Require cpu_active() in
select_task_rq(), for user tasks") select_fallback_rq() will BUG() if
the CPU to which a task has pinned itself and pinned becomes
!cpu_active() while it slept.
The task will continue running on the to-be-removed CPU and will remove
itself from the CPU during takedown_cpu() (while cpuhp_pin_lock will be
acquired) and move to another CPU based on its mask after the
migrate_disable() section has been left.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 11afaa2c618a..dba425296275 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -904,7 +904,7 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
return false;
- if (is_per_cpu_kthread(p))
+ if (is_per_cpu_kthread(p) || __migrate_disabled(p))
return cpu_online(cpu);
return cpu_active(cpu);
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