Messages in this thread | | | Date | Thu, 21 Mar 2013 23:16:09 +0100 | From | Soeren Moch <> | Subject | Re: [PATCH] USB: EHCI: fix for leaking isochronous data |
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On 21.03.2013 22:20, Andrew Lunn wrote: > On Thu, Mar 21, 2013 at 05:12:01PM -0400, Alan Stern wrote: >> On Thu, 21 Mar 2013, Alan Stern wrote: >> >>> On Thu, 21 Mar 2013, 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. >>> >>> Okay, that is a problem. But it shouldn't be such a big problem, >>> because now_frame should not be equal to 0 very often. >> >> Oh, wait, now I get it. We never reach a steady state, because the >> free list never shrinks, but occasionally it does increase when >> now_frame is equal to 0. Even though that doesn't happen very often, >> the effects add up. >> >> Very good; tomorrow I will send your patch in. > > Hi Alan, Soeren > > Could you word the description a bit better. If Alan did not get it > without a bit of thought, few others are going to understand it > without a better explanation. > > Thanks > Andrew >
Alan,
can you come up with a better explanation, please? I think your description how it is supposed to work from here http://marc.info/?l=linux-usb&m=136345559432055&w=2 is required to understand the problem and the fix.
Thanks, Soeren
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