netdev - Re: [patch] usbnet: fix 100% CPU use on suspended device

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Date:	Mon, 26 Jul 2010 18:21:14 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Elly Jones <ellyjones@...gle.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: [patch] usbnet: fix 100% CPU use on suspended device

Am Montag, 26. Juli 2010, 17:13:23 schrieb Alan Stern:
> On Mon, 26 Jul 2010, Elly Jones wrote:
> 
> > > This isn't right.  The problem should be fixed some other way.  Under
> > > what circumstances are URBs submitted incorrectly?
> > 
> > When the device is autosuspended. What is the proper thing for a
> > device to do here?
> 
> From looking at the code, it appears that the EVENT_DEV_ASLEEP flag
> should be tested in usbnet_bh() the way it is in rx_submit().  But I'm
> not an expert on usbnet; we should ask someone who is, like Oliver.

Sorry, I didn't notice this thread.

The correct way to check for autosuspend in usbnet is to look
at EVENT_DEV_ASLEEP under txq.lock. That being said, usbnet_bh()
uses rx_submit() which does the correct check. The bug seems to be
a lack of error handling in usbnet_bh() regarding the return of rx_submit()

	Regards
		Oliver
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