On 04/19, Gautham R Shenoy wrote:
>
> @@ -63,12 +74,16 @@ void refrigerator(void)
>       recalc_sigpending(); /* We sent fake signal, clean it up */
>       spin_unlock_irq(&current->sighand->siglock);
>  
> +     task_lock(current);
>       for (;;) {
>               set_current_state(TASK_UNINTERRUPTIBLE);
>               if (!frozen(current))
>                       break;
> +             task_unlock(current);
>               schedule();
> +             task_lock(current);
>       }
> +     task_unlock(current);
>       pr_debug("%s left refrigerator\n", current->comm);
>       current->state = save;

Just curious, why this change?

> +int hold_freezer_for_task(struct task_struct *p)
> +{
> +     int ret = 0;
> +     spin_lock(&freezer_status.lock);
> +     if (freezer_status.count >= 0)
> +     {
> +             set_tsk_thread_flag(p, TIF_FREEZER_HELD);
> +             thaw_process(p);
> +             freezer_status.count++;
> +             ret = 1;
> +     }
> +     spin_unlock(&freezer_status.lock);
> +
> +     return ret;
> +}

I think this can work if it is used only in kthread_stop(). But what if
another task wants to do hold_freezer_for_task(p) ? freezer_status.count
is recursive, but TIF_FREEZER_HELD is not. IOW, I believe this is not
generic enough.

Also, you are planning to add different freezing states (FE_HOTPLUG_CPU,
FE_SUSPEND, etc). In that case each of them needs a separate .count, because
it should be negative when try_to_freeze_tasks() returns. Now consider
the case when we are doing freeze_processes(FE_A | FE_B) ...

Oleg.

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