Subject: Re: ok to remove DDB_ONPANIC=1 from XEN{0,U}?
To: Jonathan A. Kollasch <>
From: Greg Troxel <>
List: current-users
Date: 12/01/2005 13:15:02
"Jonathan A. Kollasch" <> writes:

> On Thu, Dec 01, 2005 at 11:30:28AM -0500, Greg Troxel wrote to port-xen:
> > After splitting GENERIC.local/INSTALL.local, I'm going over my configs
> > and putting what I want (IPSEC, stf(4)) in GENERIC.local.   I found
> > that I also had disabled DDB_ONPANIC, and think this doesn't belong in
> > XEN's GENERIC equivalent since it is unsuitable for production.  Any
> > objections to committing the following?
> While it may be unsuitable for production, there is precedence for
> having DDB_ONPANIC set in GENERIC. All archs I know about (alpha, i386,
> macppc) have it set by default. Not having it set makes postmortem
> debugging nearly impossible. IMHO this should be unset by sysctl after
> boot if desired.

Thanks for pointing that out - I was confused.  Having "options DDB"
leads to ddb-on-panic unless one has

  options	DDB_ONPANIC=0

because src/sys/ddb/ddb_variables.c has

 * If this is non-zero, the DDB will be entered when the system
 * panics.  Initialize it so that it's patchable.
#define DDB_ONPANIC	1
int		db_onpanic = DDB_ONPANIC;

Currently pmax GENERIC sets DDB_ONPANIC to 0, but the rest of the
GENERICs don't.  I'd like to have the default be not to enter DDB on
panic because rebooting is a better response for people who haven't
thought about this.

But, I've set ddb.onpanic=0 in /etc/sysctl.conf on most of my

Still,  I think XEN* should match GENERIC unless there's a reason, in
which case there should be a comment.

        Greg Troxel <>