> On Sat, 2016-08-20 at 14:14 +0200, Julio Guerra wrote: >>>> Another example: >>>>> 00 00 00 00 00 00 00 01 >>>> ... >>>>> 01 00 00 00 00 00 00 00 >>>> ... >>>>> 00 01 00 00 00 00 00 00 >>>> ... >>>>> 00 00 01 00 00 00 00 00 >>>> after a random number of times, while usbmon shows the usb payload >>>> "00 00 00 00 00 00 00 01". >>> >>> Hi, how many bytes does read() return? >>> >> >> Exactly 8 bytes, always. I set the tty in raw non-canonical mode with >> vmin = 8 and vtime = 0. I also tried with vmin = 1 and did the copy of >> exactly 8 bytes by looping in userspace, without any improvement. >> >> I wrote a small workaround for now that detects this problem (because I >> exactly know what the buffer is supposed to look like) to close() and >> re-open() the device. The next read buffer is then correct. >> > > Please activate dynamic debugging for the tty and cdc_acm driver. > We need to know where the corruption happens. > I didn't find anything helpful in /sys/kernel/debug/dynamic_debug regarging the tty module (I enabled tty_io debugs and it doesn't appear in the logs), but I enabled cdc_acm debugs. Nothing is observable in the logs when the bug appears. I logged everything as a comment of the gist: https://gist.github.com/Julio-Guerra/b6529994f814771c825649bdb8d927c2#gistcomment-1875985 Note that re-running the script restarts the underlying kernel buffer correctly, it does not restart from its previous bugged state. Let me know if you want other debug traces enabled. -- Julio Guerra
Attachment:
signature.asc
Description: OpenPGP digital signature
