Re: anchors and their use

On Tue, 22 May 2007, Oliver Neukum wrote:

> Am Mittwoch, 16. Mai 2007 17:30 schrieb Alan Stern:
> 
> > This won't build because you forgot to export usb_unanchor_urb().
> > 
> > You could make usb_init_anchor() non-inline.  I'm not sure where 
> > tradeoff lies, but you might be over the limit.
> > 
> > I don't like the way you combined the error handling in usb-skeleton 
> > with the anchor stuff.  Better to keep the two things in separate 
> > patches.
> 
> Hi,
> 
> I hope this version addresses your concerns

Very good.  I did notice two more things:

	Timeouts are specified in jiffies, so your timeout argument
	should be long or unsigned long, not int.

	There's a race if two threads call usb_unanchor_urb() for the
	same URB at the same time.  You need to recheck while holding 
	the anchor's spinlock that urb->anchor is still equal to 
	anchor.  You might also want to add

		WARN_ON(urb->anchor != NULL);

	to usb_anchor_urb(), just as a precaution.

Alan Stern


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