On Fri, Nov 16, 2018 at 04:38:27PM -0800, Roman Gushchin wrote:
> +void cgroup_freezer_migrate_task(struct task_struct *task,
> +                              struct cgroup *src, struct cgroup *dst)
> +{
> +     lockdep_assert_held(&css_set_lock);
> +
> +     /*
> +      * Kernel threads are not supposed to be frozen at all.
> +      */
> +     if (task->flags & PF_KTHREAD)
> +             return;
> +
> +     /*
> +      * Adjust counters of freezing and frozen tasks.
> +      */
> +     if (test_bit(CGRP_FREEZE, &src->flags)) {
> +             src->freezer.nr_tasks_to_freeze--;
> +             WARN_ON_ONCE(src->freezer.nr_tasks_to_freeze < 0);
> +     }
> +
> +     /*
> +      * If the task is frozen, let's bump nr_tasks_to_freeze even
> +      * if the target cgroup isn't frozen: the counter will be decreased
> +      * in cgroup_leave_frozen().
> +      */
> +     if (test_bit(CGRP_FREEZE, &dst->flags) || task->frozen)
> +             dst->freezer.nr_tasks_to_freeze++;
> +
> +     if (task->frozen) {
> +             src->freezer.nr_frozen_tasks--;
> +             dst->freezer.nr_frozen_tasks++;
> +             WARN_ON_ONCE(src->freezer.nr_frozen_tasks < 0);
> +             WARN_ON_ONCE(dst->freezer.nr_frozen_tasks >
> +                          dst->freezer.nr_tasks_to_freeze);
> +     }

If a non-frozen task is being moved into a frozen cgroup, shouldn't
that also trigger frozen state update?

Thanks.

-- 
tejun

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