On 9/6/22 16:50, Peter Zijlstra wrote:
On Tue, Sep 06, 2022 at 04:40:03PM -0400, Waiman Long wrote: I've not followed the earlier stuff due to being unreadable; just reacting to this..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); + }This cannot be right. There might be previous set_cpus_allowed_ptr() callers that are blocked and waiting for the task to land on a valid CPU.
You are probably right. I haven't fully understand all the migration disable code yet. However, if migration is disabled, there are some corner cases we need to handle properly.
Cheers, Longman
