Messages in this thread | | | Date | Thu, 21 Mar 2013 22:45:16 +0100 | From | Soeren Moch <> | Subject | Re: [PATCH] USB: EHCI: fix for leaking isochronous data |
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On 03/21/13 22:12, 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.
Correct. Approximately twice a second we allocate 9 iTDs from the dma_pool in my case (the frame numbers run from 0 to 511 - not up to 2047, which I thought they should). But since we allocate iTDs every 8 frames in my case (for each active stream), the pool allocations occur only when we hit the allocation sequence frame 0,8,16,... (not one of the other 7 opportunities frame 1,9,17,... - frame 7,15,23,...)
> Very good; tomorrow I will send your patch in. > > Alan Stern > Thank you. And also thanks to all who helped to track down this issue.
Soeren
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