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To: Bruce Evans <bde@zeta.org.au>
cc: j@uriah.heep.sax.de, peter@jhome.dialix.com,
        CVS-committers@freefall.freebsd.org, cvs-all@freefall.freebsd.org,
        cvs-sys@freefall.freebsd.org, gpalmer@freefall.freebsd.org
Subject: Re: cvs commit: src/sys/i386/conf LINT src/sys/kern subr_prf.c 
In-reply-to: Your message of "Mon, 04 Mar 1996 23:04:30 +1100."
             <199603041204.XAA11681@godzilla.zeta.org.au> 
From: David Greenman <davidg@Root.COM>
Reply-To: davidg@Root.COM
Date: Mon, 04 Mar 1996 04:40:55 -0800
Sender: owner-cvs-sys@FreeBSD.ORG
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>>>>   Add a new option: DDB_UNATTENDED. Stops machine dropping into DDB
>>>>...
>>>I would have loved to see a sysctl variable for this instead.  This
>>>...
>
>>I agree.. It is amazingly simple to add sysctl variables after PHK's upgrade
>>of the sysctl code.  It's now as simple as adding two (or three) lines to the
>>code..  One #include, an int variable and a SYSCTL_INT(.. OID_AUTO..) line.
>
>It's almost as simple as
>
>	echo "set ddb_unattended = 1" | gdb -k -w /kernel /dev/mem
>
>:-).  Only variables that need a procdedure to set dependent variables
>can't be handled using gdb.
>
>Using a single variable to control debugger entries is actually not
>simple.  Debugger() is called from 18 modules and you don't want to
>have to change all of these and all future callers to test the variable
>and decide what to do.  The variable should probably be tested in
>Debugger() (panic if it is set), but then you need a separate entry
>point(s) to force ordinary entry to ddb from the console(s).
>Similarly for other entries to ddb (for stray trace traps, breakpoints,
>and other exceptions).  Similarly if cons_unavail is set.

   All that we really need is a "ddb_on_panic" sysctl variable. The other
cases I (and I'm sure most others) don't care about.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project