Re: kern/55774: Kernel panics if another PC is powered on with serial cable attached between two

[Andrius V <vezhlys%gmail.com@localhost>]

The following reply was made to PR kern/55774; it has been noted by GNATS.

From: Andrius V <vezhlys%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/55774: Kernel panics if another PC is powered on with serial
 cable attached between two
Date: Mon, 2 Nov 2020 20:21:39 +0200

 Hi,
 
 Yes, it is ddb on break. I didn't know about this functionality and
 somehow it took me a while to realize the pattern. Thank you for the
 help and information. The bug can be closed.
 
 Regards,
 Andrius V
 
 On Mon, Nov 2, 2020 at 7:35 AM Martin Husemann <martin%duskware.de@localhost> wrote:
 >
 > The following reply was made to PR kern/55774; it has been noted by GNATS.
 >
 > From: Martin Husemann <martin%duskware.de@localhost>
 > To: gnats-bugs%netbsd.org@localhost
 > Cc:
 > Subject: Re: kern/55774: Kernel panics if another PC is powered on with
 >  serial cable attached between two
 > Date: Mon, 2 Nov 2020 06:32:13 +0100
 >
 >  On Mon, Nov 02, 2020 at 12:55:23AM +0100, Joerg Sonnenberger wrote:
 >  > That's not a panic, but ddb-on-break?
 >
 >  Exactly. Easy workaround: set the ddb trigger sequence to something
 >  else (popular option: +++++), see cnmagic(9) for a description of
 >  the format and then set it via /etc/sysctl.conf like:
 >
 >  hw.cnmagic=+++++
 >
 >  Background: many PCs force the TX signal of all on-board com interfaces
 >  to 0V for an extended period during power on. This signals a "break"
 >  condition to the peer, and the console code reacts to it by invoking
 >  the kernel debugger.
 >
 >  Martin
 >