>Number:         503
>Category:       port-hp300
>Synopsis:       pmap related panics while doing dump/restore in singleuser
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    gnats-admin (GNATS administrator)
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 30 03:05:05 1994
>Originator:     Jason R. Thorpe
>Organization:
--------------------------------------------------------------------------
Jason R. Thorpe               thorpej@cs.orst.edu                 758-2003
Systems Administrator            CSWest Room 12                   737-2229
CS Dept, Oregon State University           http://www.cs.orst.edu/~thorpej
               "I brought my BOWLING BALL -- and some DRUGS!"
                      -- ztp
>Release:        NetBSD 1.0_BETA (sup'd approx 2 weeks ago)
>Environment:
	
System: NetBSD basalt 1.0_BETA NetBSD 1.0_BETA (BASALT) #4: Fri Sep 30 00:17:49 PDT 1994 thorpej@helix:/usr/src/sys/arch/hp300/compile/BASALT hp300

hp 380, 24meg mem, scsi, hpib, hs-hpib, dca, dcm, catseye, lan, etc.

maxusers at 24 in kernel config.

>Description:
	While bringing up my new 380, it came time to dump what was on the
	hpib disks onto the scsi disk.  I typically use dump/restore in 
	a pipeline to do this.

	After booting into single user mode, fsck -p'ing, mounting all
	physical partitions, I proceded as follows:

	# mount /dev/sd0a /mnt
	# dump 0sf 222000 - / | (cd /mnt; restore rf -)

	The dump gets through Pass I, Pass II, and does the following
	at the beginning of Pass III

	vm_fault(f1000, 7e6000, 1, 0) -> 1
	  type 8, code [mmu,,ssw]: 545
	trap type 8, code = 545, v = 7e6000
	kernel: MMU fault trap
	stopped at	_free+0x30:	movaw	(a3),a1

	a trace gives the following:

	_free
	_pmap_remove_mapping
	_pmap_enter
	_pmap_enter_ptpage
	_pmap_enter
	_vm_fault
	_pmap_enter_ptpage
	_pmap_enter
	_vm_fault
	_trap
	_addrerr

Pretty sure it's not a hardware problem - the machine, just a couple of
days ago, was running HP-UX 9.00, HP VUE, FrameMaker, etc, etc, etc.

>How-To-Repeat:
	See above.
>Fix:
	Well, I don't have a clue.  The thing is great in multiuser.

	I really believe that this is related to the `freezing'
	problems that I have on a 380 at work, which dies randomly when
	maxusers is set at 32 or higher.  Ever since I brought maxusers
	down to 16, the machine has been great.  So guess what I'm going
	to try here...I'll admit that 24 was a strange number in this
	case, and I'm wondering why I ever picked it...I guess 8 just
	sounded too low...
>Audit-Trail:
>Unformatted: