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

From: Michael Trimarchi
Date: Thu Mar 21 2013 - 15:34:49 EST


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@xxxxxx>
>> 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.


> Arnd

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