Hi Pete, for me it is fairly easy to reproduce with an ultrasound equipment we
developed in PUC-Rio university using Opalkelly FPGA cards (which include USB
ports). I can run our app + libusbx receiving tons of data for days flawless if
the highvoltage ultrasound power supply is disabled.
However, if i turn the HV power on, there will be very short +100/-100V pulses
being produced thousands times per second. This creates a lot of RF noise. With
HV power on I consistently trigger this infinite loop in a matter of minutes,
among with other transmissions errors which don't cause the app to freeze.
The software can't tell the difference if the HV power is on or off. I have
already tried reading/writing to the buffers passed to libusbx to prove they
are not invalid pointers.
If you want to perform any additional tests or try other theories please let me
know. But i think the failure is well understood: the kernel can't perform a
copy_to_user because the size of the transfer somehow got corrupted either in
outgoing request (most likely) or in incoming transfer, so it won't fit the
provided buffer that expected a different size. Still (as clearly shown in
kernel code) even if copy fails, the urb is freed there, so this explains why
cancel will also fail with this error. Then, by staying in this loop, we will
be waiting forever for a non-existent event to occur.
---
Reply to this email directly or view it on GitHub:
https://github.com/libusbx/libusbx/pull/167#issuecomment-31984952
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