usb/160436: ucom wedges machine on parity error ?

Poul-Henning Kamp phk at
Sat Sep 3 20:00:21 UTC 2011

>Number:         160436
>Category:       usb
>Synopsis:       ucom wedges machine on parity error ?
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-usb
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Sep 03 20:00:20 UTC 2011
>Originator:     Poul-Henning Kamp
>Release:        FreeBSD 8.2-STABLE i386
FreeBSD 8.2-STABLE FreeBSD 8.2-STABLE #0: Wed Aug 31 08:43:34 UTC 2011     root at  i386

	Soekris NET4801


	I'm running Soekris NET4801 doing data collection, it has been
	running stable for years.

	Recently I added a USB-serial port running in raw mode
	at 300/7/EVEN

	The machine started freezing hard and recovered only when the
	watchdog kicked in.

	When frozen, there is no serial console reaction, no packet
	traffic and no signs of a panic message.

	I tried two different USB-serial dongles, one UPLCOM and
	one UFTDI, apart from a possibly slightly different frequency,
	no difference.

	Disabling the software on the USB serial port, made the freezes
	go away.

	I have now moved the parity check into software, running the
	port as 300/8/NONE instead, and the problem has not been seen

	Has anybody ever tested a parity error on a USB serial port ?




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