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

[Martin Husemann <martin%duskware.de@localhost>]

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