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

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Message-ID: <AANLkTi=KbThErL-jXXSVGdkod-p7B7u6eDL5LtnU5SG-@mail.gmail.com>
Date:	Mon, 2 Aug 2010 09:31:33 -0400
From:	Elly Jones <ellyjones@...gle.com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	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

On Mon, Jul 26, 2010 at 12:21 PM, Oliver Neukum <oliver@...kum.org> wrote:
> 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()

If rx_submit() fails, should usbnet_bh() just not tasklet_schedule() itself?

>        Regards
>                Oliver

-- Elly
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