Strange Panic During Reboot

[Cy Schubert]

I'm getting the following panic during shutdown of a 6.1-PRERELEASE system 
cvsupped yesterday. Strangely enabling DDB in the kernel "fixes" the 
problem. The computer is an old P120 (which I should probably replace). It 
occurs every time when DDB is disabled but when DDB is enabled, it does not 
panic.

All buffers synced.
Uptime: 19m16s
(da0:ahc0:0:0:0): SYNCHRONIZE CACHE. CDB: 35 0 0 0 0 0 0 0 0 0 
(da0:ahc0:0:0:0): Sense Error Code 0xe0 at block no. -1073741792 (decimal)
kernel trap 12 with interrupts disabled


Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x1c
fault code              = supervisor write, page not present
instruction pointer     = 0x20:0xc0539553
stack pointer           = 0x28:0xc6da2a68
frame pointer           = 0x28:0xc6da2ab4
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = resume, IOPL = 0
current process         = 1728 (reboot)
trap number             = 12
panic: page fault
Uptime: 19m16s

I suspect that memory is mapped a tiny bit differently with DDB enabled and 
thus we don't tickle a bug somewhere.

Thoughts?



-- 
Regards,                         Phone:  (250)387-8437
Cy Schubert                        Fax:  (250)387-5231
Team Leader, Solaris Team        Email:  Cy.Schubert at osg.gov.bc.ca
Open Systems Group, CITS
Ministry of Labour and Citizens' Services
Province of BC            
                    FreeBSD UNIX:  cy at FreeBSD.org