USB_KILL_URB(9) 						   USB Core APIs						   USB_KILL_URB(9)

NAME

       usb_kill_urb - cancel a transfer request and wait for it to finish

SYNOPSIS

       void usb_kill_urb(struct urb * urb);

ARGUMENTS

       urb
	   pointer to URB describing a previously submitted request, may be NULL

DESCRIPTION

       This routine cancels an in-progress request. It is guaranteed that upon return all completion handlers will have finished and the URB will
       be totally idle and available for reuse. These features make this an ideal way to stop I/O in a disconnect callback or close function. If
       the request has not already finished or been unlinked the completion handler will see urb->status == -ENOENT.

       While the routine is running, attempts to resubmit the URB will fail with error -EPERM. Thus even if the URB's completion handler always
       tries to resubmit, it will not succeed and the URB will become idle.

       The URB must not be deallocated while this routine is running. In particular, when a driver calls this routine, it must insure that the
       completion handler cannot deallocate the URB.

       This routine may not be used in an interrupt context (such as a bottom half or a completion handler), or when holding a spinlock, or in
       other situations where the caller can't schedule.

       This routine should not be called by a driver after its disconnect method has returned.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							   USB_KILL_URB(9)