Re: Question about hub_thread

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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