Re: [BUG v4.14-rt] kernel BUG at /work/rt/stable-rt.git/kernel/sched/core.c:1639!

[Mike Galbraith]

On Sat, 2018-08-18 at 15:13 +0200, Mike Galbraith wrote:
> seems it has be something from the 4.17 cycle that went back to 4.14-
> stable after 4.1[56]-stable trees went extinct.

See ("sched/core: Require cpu_active() in select_task_rq(), for user tasks")

Fix it like so?

sched: Allow pinned user tasks to be awakened to the CPU they pinned

Since 7af443ee16976, select_fallback_rq() will BUG() if the CPU to
which a task has pinned itself and pinned becomes !cpu_active()
while it slept.  Serving a 10 megaton eviction notice is neither
helpful nor required, the task will migrate when it can do so.

Signed-off-by: Mike Galbraith <efault@xxxxxx>
---
 kernel/sched/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -980,7 +980,7 @@ static inline bool is_cpu_allowed(struct
 	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);