From: Mike Galbraith Date: Sun, 19 Aug 2018 08:28:35 +0200 Subject: [PATCH] sched: Allow pinned user tasks to be awakened to the CPU they pinned Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.1-rt3.tar.xz 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 Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -903,7 +903,7 @@ 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);