On 5 Sep 2022 10:47:36 +0800 Jing-Ting Wu <jing-ting.wu@xxxxxxxxxxxx> wrote
>
> We meet the HANG_DETECT happened in T SW version with kernel-5.15.
> Many tasks have been blocked for a long time.
>
> Root cause:
> migration_cpu_stop() is not complete due to is_migration_disabled(p) is
> true, complete is false and complete_all() never get executed.
> It let other task wait the rwsem.
See if handing task over to stopper again in case of migration disabled
could survive your tests.
Hillf
--- linux-5.15/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2322,9 +2322,7 @@ static int migration_cpu_stop(void *data
* holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
* we're holding p->pi_lock.
*/
- if (task_rq(p) == rq) {
- if (is_migration_disabled(p))
- goto out;
+ if (task_rq(p) == rq && !is_migration_disabled(p)) {
if (pending) {
p->migration_pending = NULL;
