Re: limits of usb_kill_urb()
Alan Stern <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Thu, 15 Mar 2007, Oliver Neukum wrote: > Hi, > > I am looking at code in which an interrupt completion handler can either > > a) resubmit itself > b) submit a control URB > > the control URB will in turn submit the interrupt URB again. > > It seems to me that usb_kill_urb() alone cannot be used to cancel IO > without a race condition, as the following race always exists. Yes, certainly. usb_kill_urb() handles only the common case. > This problem exists if more than two URBs are involved, too. If you take > completion as nodes in a directed graph and submissions as edges, you > need to watch for cycles. > > Comments? Should I add a warning to Documentation/URB.txt? It wouldn't be a bad idea to do so. Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel