Hi Chris,
thanks for the error report.
There seems to be a missing ep_unlink() somewhere
(or the ep_unlink doesn't really unlink every ed,
or there is a race between ep_link and ep_unlink).
So we have to find the place where the unlink is missing ...
thanks
Roman
Parrott, Chris wrote:
> Greetings:
>
> I encountered an apparent bug in the OHCI host controller driver in Linux.
> This one appears as a hang after I open, close, open, close, and then open a
> Belkin USB serial adapter device attached to the USB with a Compaq OHCI USB
> host controller chip. I originally discovered this problem while attempting
> to spawn gettys on the serial adapter. I subsequently reduced it down to
> just this sequence of operations.
>
> The Belkin serial adapter has two bulk endpoints (one in, one out) and one
> interrupt endpoint (in). The hang occurs when sohci_submit_urb() in
> usb-ohci.c calls ep_link() to link the interrupt endpoint descriptor into
> the OHCI interrupt descriptor tree. For some reason, the endpoint
> descriptor is linked with hwNextED pointing back at itself, which creates an
> infinite loop in the schedule. When the OHCI hardware tries to execute this
> schedule, you get the system hang.
>
> I have created a fix which just checks to see if the endpoint descriptor is
> already linked into the tree, and if so, then nothing else should happen.
> This seems more like a band-aid than a proper fix to me, so I would welcome
> any comments as to how this might be improved to better deal with the
> situation. I would also like to know if this attempted fix would cause any
> unintended breakage that I am not aware of.
>
> The following patch should work against most recent 2.4.x kernels. I used a
> 2.4.8 tree for this one.
>
> Many thanks in advance,
>
> +chris
>
> Chris Parrott
> Linux Software Engineer
> EchoStar Technologies Corp.
> 94 Inverness Terrace East, Englewood, CO 80112
> phone: (303) 706-5383
> email: [EMAIL PROTECTED]
>
>
>
> --- linux/drivers/usb/usb-ohci.c.old Mon Oct 29 14:20:06 2001
> +++ linux/drivers/usb/usb-ohci.c Mon Oct 29 14:22:27 2001
> @@ -1023,9 +1023,13 @@
> inter = 1;
> for (ed_p = &(ohci->hcca->int_table[ep_rev (5, i) +
> int_branch]);
> (*ed_p != 0) && ((dma_to_ed (ohci,
> le32_to_cpup (ed_p)))->int_interval >= interval);
> - ed_p = &((dma_to_ed (ohci, le32_to_cpup
> (ed_p)))->hwNextED))
> + ed_p = &((dma_to_ed (ohci, le32_to_cpup
> (ed_p)))->hwNextED)) {
> inter = ep_rev (6, (dma_to_ed (ohci,
> le32_to_cpup (ed_p)))->int_interval);
> - ed->hwNextED = *ed_p;
> + if (*ed_p == ed->dma)
> + break;
> + }
> + if (*ed_p != ed->dma)
> + ed->hwNextED = *ed_p;
> *ed_p = cpu_to_le32 (ed->dma);
> }
> #ifdef DEBUG
>
>
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>
>
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