From 93c4258bc009109bee258c30fa2a53680c8b1f9a Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Thu, 26 Aug 2021 15:37:38 +0200 Subject: [PATCH 299/323] sched: Fix get_push_task() vs migrate_disable() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz push_rt_task() attempts to move the currently running task away if the next runnable task has migration disabled and therefore is pinned on the current CPU. The current task is retrieved via get_push_task() which only checks for nr_cpus_allowed == 1, but does not check whether the task has migration disabled and therefore cannot be moved either. The consequence is a pointless invocation of the migration thread which correctly observes that the task cannot be moved. Return NULL if the task has migration disabled and cannot be moved to another CPU. Cc: stable-rt@vger.kernel.org Fixes: a7c81556ec4d3 ("sched: Fix migrate_disable() vs rt/dl balancing") Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210826133738.yiotqbtdaxzjsnfj@linutronix.de Signed-off-by: Steven Rostedt (VMware) --- kernel/sched/sched.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ad854a670701..bda12827832e 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1949,6 +1949,9 @@ static inline struct task_struct *get_push_task(struct rq *rq) if (p->nr_cpus_allowed == 1) return NULL; + if (p->migration_disabled) + return NULL; + rq->push_busy = true; return get_task_struct(p); } -- 2.43.0