On Tue, 16 Sep 2014, Joe Lawrence wrote:
> > Anyway, the log above means that a QH was linked before the HC died,
> > but then it was never unlinked. Please add a line at the start of
> > ehci_endpoint_disable, printing out the value of ep->hcpriv for
> > comparison with the values listed above.
>
> Will do.
>
> > Also, let's see the contents of *qh and *(qh->hw) for the left-over QH
> > at *(ehci->async->qh_next.qh). You can get those right away from your
> > crash dump data, right?
>
> Yep, interestingly enough, *(ehci->async->qh_next.qh) appears to be
> mostly full of zeros:
> crash> struct ehci_qh 0xffff88083d6b4558 << *(ehci->async->qh_next.qh)
> struct ehci_qh {
> hw = 0x0,
> qh_dma = 0x0,
> qh_next = {
> qh = 0x0,
> itd = 0x0,
> sitd = 0x0,
> fstn = 0x0,
> hw_next = 0x0,
> ptr = 0x0
> },
> qtd_list = {
> next = 0x0,
> prev = 0x0
> },
> intr_node = {
> next = 0x0,
> prev = 0x0
> },
> dummy = 0x0,
> unlink_node = {
> next = 0x0,
> prev = 0x0
> },
> unlink_cycle = 0x6,
> qh_state = 0x0,
> xacterrs = 0x0,
> usecs = 0x0,
> gap_uf = 0x0,
> c_usecs = 0x0,
> tt_usecs = 0x0,
> period = 0x0,
> start = 0x0,
> dev = 0x6,
> is_out = 0x0,
> clearing_tt = 0x0,
> dequeue_during_giveback = 0x0,
> exception = 0x0
> }
So this QH was destroyed properly, but somehow the link pointer in
ehci->async continued to point at it. And it got destroyed without
passing through single_unlink_async.
Maybe you should also add a check at the end of ehci_endpoint_disable,
just before the done: label. For example,
BUG_ON(ehci->async->qh_next.qh == qh);
Then if you really want to be thorough, in single_unlink_async, just
after the "while" loop, print the values of prev, prev->qh_next.qh, qh,
and qh->qh_next.qh. And in qh_link_async, just after the wmb(), print
the values of head->qh_next.qh and qh. (This could end up generating
quite a lot of output...)
Alan Stern
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