netdev - Re: [PATCHv5] usbnet: Resubmit interrupt URB once if halted

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Message-Id: <201104240836.47491.oliver@neukum.org>
Date:	Sun, 24 Apr 2011 08:36:47 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Paul Stewart <pstew@...omium.org>
Cc:	Alan Stern <stern@...land.harvard.edu>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, davem@...emloft.net,
	bhutchings@...arflare.com
Subject: Re: [PATCHv5] usbnet: Resubmit interrupt URB once if halted

Am Freitag, 22. April 2011, 17:59:15 schrieb Paul Stewart:
> >
> >>       free_netdev(net);
> >>       usb_put_dev (xdev);
> >>  }
> >> @@ -1285,6 +1291,10 @@ int usbnet_suspend (struct usb_interface *intf, pm_message_t message)
> >>                * wake the device
> >>                */
> >>               netif_device_attach (dev->net);
> >> +
> >> +             /* Stop interrupt URBs */
> >> +             if (dev->interrupt)
> >> +                     usb_kill_urb(dev->interrupt);
> >>       }
> >>       return 0;
> >>  }
> >
> > There is a subtle question here: When is the best time to kill the
> > interrupt URB?  Without knowing any of the details, I'd guess that the
> > interrupt URB reports asynchronous events and the driver could run into
> > trouble if one of those events occurred while everything else was
> > turned off.  This suggests that the interrupt URB should be killed as
> > soon as possible rather than as late as possible.  But maybe it doesn't
> > matter; it all depends on the design of the driver.
> 
> I'm not sure I can answer this question either.  As it stands, nobody
> was killing them before.  Just trying to make it better.

Hm. Are we looking at the same code? usbnet_suspend now has:

		/*
		 * accelerate emptying of the rx and queues, to avoid
		 * having everything error out.
		 */
		netif_device_detach (dev->net);
		usbnet_terminate_urbs(dev);
		usb_kill_urb(dev->interrupt);

This suggests that if you want to resubmit the interrupt URB in resume()
you do it first. Which drivers use the interrupt URB?

	Regards
		Oliver
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