linux-kernel - Re: [PATCH] USB: EHCI: fix for leaking isochronous data

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Date:	Thu, 21 Mar 2013 20:34:39 +0100
From:	Michael Trimarchi <michael@...rulasolutions.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Jason Cooper <jason@...edaemon.net>, Soeren Moch <smoch@....de>,
	Alan Stern <stern@...land.harvard.edu>,
	USB list <linux-usb@...r.kernel.org>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-mm@...ck.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] USB: EHCI: fix for leaking isochronous data

Hi

On 21/03/13 20:10, Arnd Bergmann wrote:
> On Thursday 21 March 2013, Jason Cooper wrote:
>> On Thu, Mar 21, 2013 at 06:04:59PM +0100, Soeren Moch wrote:
> 
>>>
>>> Now I found out what is going on here:
>>>
>>> In itd_urb_transaction() we allocate 9 iTDs for each URB with
>>> number_of_packets == 64 in my case. The iTDs are added to
>>> sched->td_list. For a frame-aligned scheduling we need 8 iTDs, the
>>> 9th one is released back to the front of the streams free_list in
>>> iso_sched_free(). This iTD was cleared after allocation and has a
>>> frame number of 0 now. So for each allocation when now_frame == 0 we
>>> allocate from the dma_pool, not from the free_list. The attached
>>> patch invalidates the frame number in each iTD before it is sent to
>>> the scheduler. This fixes the problem without the need to iterate
>>> over a iTD list.
>>>
>>> Signed-off-by: Soeren Moch <smoch@....de>
>>
>> Wow!  Great work Soeren!  Talk about a long road to a small fix.  Thanks
>> for keeping after it.
> 
> +1
> 
> I hardly understand half of the description above, but that much sounds
> plausible. Is this a bug fix that should get backported to stable kernels?
> 

+ 1
and I can test on my device. Just one comment:
I don't know if -1 is the correct way to init it.

Michael

> 	Arnd
> 

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