Re: cn_queue.c

[Andrew Morton <akpm@osdl.org>]

Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
>
> cn_queue_free_dev() will wait until dev->refcnt hits zero 
>  before freeing any resources,
>  but it can happen only after cn_queue_del_callback() does 
>  it's work on given callback device [actually when all callbacks 
>  are removed].
>  When new callback is added into device, it's refcnt is incremented
>  [before adition btw, if addition fails in the middle, reference is
>  decremented], when callbak is removed, device's reference counter
>  is decremented aromically after all work is finished.

hm.

How come cn_queue_del_callback() uses all those barriers if no other CPU
can grab new references against cbq->cb->refcnt?

cn_queue_free_callback() forgot to do flush_workqueue(), so
cn_queue_wrapper() can still be running while cn_queue_free_callback()
frees up the cn_callback_entry, I think.