Since an update to kernel 3.13 my system suffers from a bug, probably
in the EHCI scheduler. I have an em28xx based DVB USB stick which is
connected to a EHCI host and uses an isochronous endpoint to transfer
data from the device to the host. Initially I thought this to be related
to the em28xx module itself, and posted a bug report there [1].
Enabling some additional debug information showed the EHCI scheduler
overflow:
kernel: ehci-pci 0000:00:1d.0: request ffff8800ccc59000 would overflow
(8136+63 >= 8192)
My best guess is that some URB's are not removed from the queue, but my
device driver keeps submitting them when opening a new stream. It does
not seem to happen during a stream (i.e. when resubmitting a completed
URB). It only occurs when opening and closing streams repeatedly (i.e.
when stopping and submitting URB's). So maybe kill()ing or stopping
URB's does not work properly.
My hardware information is attached to the bug report. I'm using an
Intel NUC (Celeron), with a QS77 chipset. I cannot reproduce the bug on
a 3.12 kernel (Arch Linux; kernel 3.12.8-1). Looking at the recent
kernel I cannot find any updates since then, and nobody reported this as
a bug as far as I know. So it might be related to my specific hardware,
although someone else reported the same problem in 3.13 kernels in the
bug report [1].
[1] https://bugzilla.kernel.org/show_bug.cgi?id=72891
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