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

From: Arnd Bergmann
Date: Thu Mar 21 2013 - 15:11:24 EST

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.


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?

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