Messages in this thread Patch in this message | | | Date | Thu, 21 Mar 2013 18:04:59 +0100 | From | Soeren Moch <> | Subject | Re: [PATCH] USB: EHCI: fix for leaking isochronous data |
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On 03/17/13 18:36, Alan Stern wrote: > On Sun, 17 Mar 2013, Soeren Moch wrote: > >> For each device only one isochronous endpoint is used (EP IN4, 1x 940 >> Bytes, Interval 1). >> When the ENOMEM error occurs, a huge number of iTDs is in the free_list >> of one stream. This number is much higher than the 2*M entries, which >> should be there according to your description. > > Okay, but how did they get there? With each URB requiring 9 iTDs, and > about 5 URBs active at any time, there should be about 5*9 = 45 iTDs in > use and 2*9 = 18 iTDs on the free list. By the time each URB > completes, it should have released all 9 iTDs back to the free list, > and each time an URB is submitted, it should be able to acquire all 9 > of the iTDs that it needs from the free list -- it shouldn't have to > allocate any from the DMA pool. > > Looks like you'll have to investigate what's going on inside > itd_urb_transaction(). Print out some useful information whenever the > size of stream->free_list is above 50, such as the value of num_itds, > how many of the loop iterations could get an iTD from the free list, > and the value of itd->frame in the case where the "goto alloc_itd" > statement is followed. > > It might be a good idea also to print out the size of the free list in > itd_complete(), where it calls ehci_urb_done(), and include the value > of ehci->now_frame. >
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@web.de>
--- linux-3.9.0-rc3-guru/drivers/usb/host/ehci-sched.c.orig 2013-03-21 17:36:21.000000000 +0100 +++ linux-3.9.0-rc3-guru/drivers/usb/host/ehci-sched.c 2013-03-21 17:38:56.000000000 +0100 @@ -1214,6 +1214,7 @@ itd_urb_transaction ( memset (itd, 0, sizeof *itd); itd->itd_dma = itd_dma; + itd->frame = -1; list_add (&itd->itd_list, &sched->td_list); } spin_unlock_irqrestore (&ehci->lock, flags); @@ -1915,6 +1916,7 @@ sitd_urb_transaction ( memset (sitd, 0, sizeof *sitd); sitd->sitd_dma = sitd_dma; + sitd->frame = -1; list_add (&sitd->sitd_list, &iso_sched->td_list); } | |