On Wed, 28 Nov 2012, Vivek Bhagat wrote:
> Hi Alan,
>
> In function usb_hcd_giveback_urb() , urb completion handler is called first
> followed by decrement of urb->use_count .
> usb_hcd_giveback_urb(){
> ...
> urb->complete (urb);
> atomic_dec (&urb->use_count);
> ...
> }
>
> In urb completion handler , urb is re-submitted , urb ref count is
> incremented to a value of 2 first and then usb_hcd_giveback_urb reduces
> urb->ref_count to 1 .
> I think urb ref count should be decremented first followed by urb
> completion handler call as below :-
>
> usb_hcd_giveback_urb(){
> ...
> atomic_dec (&urb->use_count);
> urb->complete (urb);
> ...
> }
>
> Please let me know if i am missing something .
>
> Thanks,
> Vivek
On Wed, 28 Nov 2012, amit nagal wrote:
> On Thu, Nov 22, 2012 at 6:50 PM, naveen yadav <yad.naveen@xxxxxxxxx> wrote:
> > urb_count is incremented at only one place in usb_hcd_submit_urb() and
> > decremented in usb_hcd_giveback_urb(). (Also, in error case inside
> > usb_hcd_submit_urb()). After taking print of urb->use_count at all
> Hi Alan ,
>
> In function usb_hcd_giveback_urb() , urb completion handler is called
> first followed by decrement of
> urb->use_count as follow :
> usb_hcd_giveback_urb(){
> ...
> urb->complete (urb);
> atomic_dec (&urb->use_count);
> ...
> }
>
> In urb completion handler , urb is re-submitted , so urb->use_count is
> incremented to a value of 2 first and then usb_hcd_giveback_urb
> reduces urb->use_count to 1 . As urb processing is complete by the
> time urb->complete()
> is called , I think urb->use_count should be decremented first
> followed by urb completion handler call as below :-
>
> usb_hcd_giveback_urb(){
> ...
> atomic_dec (&urb->use_count);
> urb->complete (urb);
> ...
> }
>
> Please let me know if i am missing something .
>
> Thanks,
> Amit Nagal
Vivek and Amit, are you two copies of the same person?
Anyway, you're both right that urb->use_count is not decremented until
after the completion routine returns. But Amit wrote:
> As urb processing is complete by the
> time urb->complete()
> is called , I think urb->use_count should be decremented first
> followed by urb completion handler call as below :-
This is wrong. Processing continues during urb->complete, which may
even resubmit the URB.
Now, maybe your problem is that somehow urb->reject is getting set to 0
at the wrong time. You should check its value as well as the value of
urb->use_count.
Alan Stern
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