On Sat, 4 Jul 2009, Ramya Desai wrote:

quoted text
> Dear Experts,
> 
> I am trying to create a new URB in the completion call back.
> Here I am giving the code that I am using.
> 
> void my_usb_stor_blocking_completion(struct urb *urb)
> {
> 
> struct urb *rr_urb ;
> 
> //
> //
> //
> 
> 	rr_urb = (struct urb*)kmalloc(sizeof(struct urb), GFP_KERNEL);

Don't use kmalloc to allocate URBs; use usb_alloc_urb.

You must not use GFP_KERNEL in a completion routine.  Use GFP_ATOMIC 
instead.

quoted text
>                 if( NULL == rr_urb)
>                    return -ENOMEM;

You can't return -ENOMEM because this function returns void.

quoted text
>                 memcpy(rr_urb, urb, sizeof(struct urb));

Why do the memcpy?  usb_fill_bulk_urb will just overwrite the data.

quoted text
>                 usb_fill_bulk_urb(rr_urb,
> current_urb_context->pusb_dev, current_urb_context->stat_bulkin_pipe,
> prd_ready, 4,
> 		      			my_usb_stor_blocking_completion,(void*)current_urb_context);
> 
> //
> //
> //
> 
> }
> 
> With this code, the system is going to hanging.
> Is there any thing I need to do while creating a URB ?

Fix those mistakes.  No other special action is needed.

In fact, you might not have to create a new URB at all.  You might be 
able to re-use the URB that was passed to 
my_usb_stor_blocking_completion().

Alan Stern

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