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Re: install/46355: Should INSTALL kernels drop to DDB on panic?
The following reply was made to PR install/46355; it has been noted by GNATS.
From: Martin Husemann <martin%duskware.de@localhost>
Subject: Re: install/46355: Should INSTALL kernels drop to DDB on panic?
Date: Thu, 19 Apr 2012 09:49:49 +0200
On Thu, Apr 19, 2012 at 05:55:00AM +0000, Matthew Mondor wrote:
> I noticed that the INSTALL kernel includes the GENERIC config file,
> which defaults to dump core on panic. Thus, INSTALL will attempt to
> drop core instead of entering DDB if it panics at boot.
No, it will not, but let's make a short detour:
The original plan was: make the kernel drop to ddb by default, but then,
once /etc/rc runs and we have a working disk, switch to "dump core".
# Default on panic: dump core and reboot. See savecore(8) for information.
# Switch this to 1 if you want to enter the kernel debugger on crashes
# instead. See ddb(4) for an introduction and also try the "help" command
# at the db> prompt.
# If you understand the implication and want to change the behaviour before
# /etc/rc.d/sysctl is run, use the kernel option DDB_ONPANIC, see options(4).
So short summary: all GENERIC/MODULAR kernels should effectively have
DDB_ONPANIC=1 (or 2) as default, but 1 is the default if the option is
missing (see src/sys/ddb/db_variables.c). It seems that the kernels we
use for install do not have the option, so everything should be fine.
If you see an instant reboot instead of ddb somewhere after a panic,
something else is wrong.
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