On Fri, 10 Aug 2007, jidong xiao wrote:
> Here are the piece of code from 2.6.22.1,
>
> 2817 static int hub_thread(void *__unused)
> 2818 {
> 2819 do {
> 2820 hub_events();
> 2821 wait_event_interruptible(khubd_wait,
> 2822 !list_empty(&hub_event_list) ||
> 2823 kthread_should_stop());
> 2824 try_to_freeze();
> 2825 } while (!kthread_should_stop() ||
> !list_empty(&hub_event_list)) ;
> 2826
> 2827 pr_debug("%s: khubd exiting\n", usbcore_name);
> 2828 return 0;
> 2829 }
>
> I have a question.
>
> try_to_freeze should be the only way for this thread to go suspended.
>
> If we have already gone sleeping via wait_event_interruptible(), then
> if there is signal to wakeup this thread and ask it to go to
> suspended,then wait_event_interruptible will return and
> try_to_freeze() will be invoked and hence this thread will go into
> refrigerator.
>
> But if we are still running inside hub_events(),then if we received
> any signal, what will happen?still try_to_freeze will be executed?why?
Nothing will happen. The thread will continue to run inside
hub_events() and it won't freeze until hub_events() returns.
Alan Stern
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