kern/38873: ddb(4) 'next' command is noisy and slow

[dyoung%cuw.ojctech.com@localhost]

>Number:         38873
>Category:       kern
>Synopsis:       ddb(4) 'next' command is noisy and slow
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 05 22:25:00 +0000 2008
>Originator:     David Young
>Release:        NetBSD 4.99.64
>Organization:
OJC Technologies
>Environment:
System: NetBSD cuw 4.99.64 NetBSD 4.99.64 (elan) #321: Thu Jun  5 15:13:10 CDT 
2008  
dyoung%cuw.ojctech.com@localhost:/u5/dyoung-scratch/scratch-pm/i386/O/sys/arch/i386/compile/elan
 i386
Architecture: i386
Machine: i386
>Description:
With recent changes to ddb(4) and/or trap handling, there is a lot of
console noise while the ddb(4) 'next' command runs, for example,

db{0}> next 
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247901 cs c0240008 eflags 392 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247903 cs 8 eflags 392 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247904 cs c0240008 eflags 392 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247905 cs c0240008 eflags 392 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247906 cs c0240008 eflags 392 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c0247909 cs c06d0008 eflags 396 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c024790c cs 8 eflags 396 cr2 bbbb3633 ilevel 6
fatal trace trap in supervisor mode
trap type 5 code 0 eip c024790f cs 8 eflags 396 cr2 bbbb3633 ilevel 6

This disrupts the "flow" of a ddb(4) session.  It also slows
debugging on a 19200-bps serial console.

>How-To-Repeat:
Break to debugger.  Type 'next'.
>Fix: