Messages in this thread Patch in this message | | | Date | Tue, 6 Sep 2022 16:40:03 -0400 | Subject | Re: BUG: HANG_DETECT waiting for migration_cpu_stop() complete | From | Waiman Long <> |
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On 9/6/22 16:01, Waiman Long wrote: > On 9/6/22 14:30, Tejun Heo wrote: >> Hello, >> >> (cc'ing Waiman in case he has a better idea) >> >> On Mon, Sep 05, 2022 at 04:22:29PM +0800, Jing-Ting Wu wrote: >>> https://lore.kernel.org/lkml/YvrWaml3F+x9Dk+T@slm.duckdns.org/ is for >>> fix cgroup_threadgroup_rwsem <-> cpus_read_lock() deadlock. >>> But this issue is cgroup_threadgroup_rwsem <-> cpuset_rwsem deadlock. >> If I'm understanding what you're writing correctly, this isn't a >> deadlock. >> The cpuset_hotplug_workfn simply isn't being woken up while holding >> cpuset_rwsem and others are just waiting for that lock to be released. > > I believe it is probably a bug in the scheduler core code. > __set_cpus_allowed_ptr_locked() calls affine_move_task() to move to a > random cpu within the new set allowable CPUs. However, if migration is > disabled, it shouldn't call affine_move_task() at all. Instead, I > would suggest that if the current cpu is within the new allowable > cpus, it should just skip doing affine_move_task(). Otherwise, it > should fail __set_cpus_allowed_ptr_locked().
Maybe like
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 838623b68031..5d9ea1553ec0 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2794,9 +2794,9 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p, if (cpumask_equal(&p->cpus_mask, new_mask)) goto out;
- if (WARN_ON_ONCE(p == current && - is_migration_disabled(p) && - !cpumask_test_cpu(task_cpu(p), new_mask))) { + if (is_migration_disabled(p) && + !cpumask_test_cpu(task_cpu(p), new_mask)) { + WARN_ON_ONCE(p == current); ret = -EBUSY; goto out; } @@ -2818,7 +2818,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p, if (flags & SCA_USER) user_mask = clear_user_cpus_ptr(p);
- ret = affine_move_task(rq, p, rf, dest_cpu, flags); + if (!is_migration_disabled(p) || (flags & SCA_MIGRATE_ENABLE)) { + ret = affine_move_task(rq, p, rf, dest_cpu, flags); + } else { + task_rq_unlock(rq, p, rf); + }
kfree(user_mask);
I haven't tested it myself, though. Cheers, Longman
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