Bug 18303

Kernel panics when issuing
dd if=/dev/zero of=/dev/da0e count=1024

Has been repeated 5-6 times in row.

SCSI adapter is Adaptec 2940UW with two
IBM SCSI disks.
Additional info:
$dmesg
Copyright (c) 1992-1999 FreeBSD Inc.
Copyright (c) 1982, 1986, 1989, 1991, 1993
        The Regents of the University of California. All rights reserved.
FreeBSD 3.4-RELEASE #0: Thu Dec 30 02:57:15 GMT 1999
    jkh@highwing.cdrom.com:/usr/src/sys/compile/GENERIC
Timecounter "i8254"  frequency 1193182 Hz
CPU: AMD-K6(tm) 3D processor (451.02-MHz 586-class CPU)
  Origin = "AuthenticAMD"  Id = 0x58c  Stepping = 12
  Features=0x8021bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,PGE,MMX>
  AMD Features=0x80000800<SYSCALL,3DNow!>
real memory  = 268435456 (262144K bytes)
config> di zp0
config> di ze0
config> di lnc0
config> di le0
config> di ie0
config> di fe0
config> di ex0
config> di ep0
config> di ed0
config> di cs0
config> di wt0
config> di scd0
config> di mcd0
config> di matcdc0
config> di fdc0
config> di bt0
config> di aic0
config> di aha0
config> di adv0
config> q
avail memory = 257769472 (251728K bytes)
Preloaded elf kernel "kernel" at 0xc035c000.
Preloaded userconfig_script "/boot/kernel.conf" at 0xc035c09c.
Probing for devices on PCI bus 0:
chip0: <AcerLabs M1541 (Aladdin-V) PCI host bridge> rev 0x04 on pci0.0.0
chip1: <AcerLabs M5243 PCI-PCI bridge> rev 0x04 on pci0.1.0
chip2: <AcerLabs M15x3 Power Management Unit> rev 0x00 on pci0.3.0
chip3: <AcerLabs M1533 portable PCI-ISA bridge> rev 0xc3 on pci0.7.0
ahc0: <Adaptec 2940 Pro Ultra SCSI adapter> rev 0x01 int a irq 12 on pci0.9.0
ahc0: aic7880 Wide Channel A, SCSI Id=7, 16/255 SCBs
xl0: <3Com 3c905C-TX Fast Etherlink XL> rev 0x78 int a irq 10 on pci0.11.0
xl0: Ethernet address: 00:50:da:de:fe:79
xl0: autoneg complete, link status good (half-duplex, 100Mbps)
ide_pci0: <Acer Aladdin IV/V (M5229) Bus-master IDE controller> rev 0xc1 int a irq 0 on pci0.15.0
Probing for devices on PCI bus 1:
vga0: <Matrox model 1001 graphics accelerator> rev 0x02 int a irq 11 on pci1.0.0
Probing for PnP devices:
Probing for devices on the ISA bus:
sc0 on isa
sc0: VGA color <16 virtual consoles, flags=0x0>
atkbdc0 at 0x60-0x6f on motherboard
atkbd0 irq 1 on isa
psm0 not found
sio0 at 0x3f8-0x3ff irq 4 flags 0x10 on isa
sio0: type 16550A
sio1 at 0x2f8-0x2ff irq 3 on isa
sio1: type 16550A
wdc0 at 0x1f0-0x1f7 irq 14 on isa
wdc0: unit 0 (wd0): <ST34313A>
wd0: 4126MB (8452080 sectors), 8944 cyls, 15 heads, 63 S/T, 512 B/S
wdc1 at 0x170-0x177 irq 15 on isa
wdc1: unit 0 (atapi): <ASUS CD-S400/A/V1.1C>, removable, accel, dma, iordy
acd0: drive speed 6531 - 6875KB/sec, 128KB cache
acd0: supported read types: CD-R, CD-RW, CD-DA
acd0: Audio: play, 255 volume levels
acd0: Mechanism: ejectable tray
acd0: Medium: CD-ROM 120mm data disc loaded, unlocked
ppc0 at 0x378 irq 7 flags 0x40 on isa
ppc0: SMC-like chipset (ECP/EPP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 16/16/7 bytes threshold
lpt0: <generic printer> on ppbus 0
lpt0: Interrupt-driven port
ppi0: <generic parallel i/o> on ppbus 0
plip0: <PLIP network interface> on ppbus 0
vga0 at 0x3b0-0x3df maddr 0xa0000 msize 131072 on isa
npx0 on motherboard
npx0: INT 16 interface
Waiting 15 seconds for SCSI devices to settle
changing root device to wd0s1a
WARNING: / was not properly dismounted
da1 at ahc0 bus 0 target 6 lun 0
da1: <IBM DNES-318350W SA30> Fixed Direct Access SCSI-3 device
da1: 40.000MB/s transfers (20.000MHz, offset 8, 16bit), Tagged Queueing Enabled
da1: 17501MB (35843670 512 byte sectors: 64H 32S/T 17501C)
da0 at ahc0 bus 0 target 5 lun 0
da0: <IBM DNES-318350W SA30> Fixed Direct Access SCSI-3 device
da0: 40.000MB/s transfers (20.000MHz, offset 8, 16bit), Tagged Queueing Enabled
da0: 17501MB (35843670 512 byte sectors: 64H 32S/T 17501C)

$ fdisk /dev/da0
******* Working on device /dev/da0 *******
parameters extracted from in-core disklabel are:
cylinders=306356 heads=13 sectors/track=9 (117 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=306356 heads=13 sectors/track=9 (117 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165,(FreeBSD/NetBSD/386BSD)
    start 0, size 35843670 (17501 Meg), flag 80 (active)
        beg: cyl 0/ sector 1/ head 0;
        end: cyl 1023/ sector 9/ head 12
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
$ fdisk /dev/da1
******* Working on device /dev/da1 *******
parameters extracted from in-core disklabel are:
cylinders=306356 heads=13 sectors/track=9 (117 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=306356 heads=13 sectors/track=9 (117 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165,(FreeBSD/NetBSD/386BSD)
    start 0, size 35843670 (17501 Meg), flag 80 (active)
        beg: cyl 0/ sector 1/ head 0;
        end: cyl 1023/ sector 9/ head 12
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>

# /dev/da0c:
type: SCSI
disk: da0s1
label:
flags:
bytes/sector: 512
sectors/track: 9
tracks/cylinder: 43
sectors/cylinder: 387
cylinders: 92619
sectors/unit: 35843670
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # milliseconds
track-to-track seek: 0  # milliseconds
drivedata: 0

8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 35843670        0    unused        0     0         # (Cyl.    0 - 92619*)
  e:  2097152        0     vinum                        # (Cyl.    0 - 5418*)
  f: 33746518  2097152     vinum                        # (Cyl. 5418*- 92619*)
$ disklabel /dev/da1c
# /dev/da1c:
type: SCSI
disk: da1s1
label:
flags:
bytes/sector: 512
sectors/track: 9
tracks/cylinder: 43
sectors/cylinder: 387
cylinders: 92619
sectors/unit: 35843670
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # milliseconds
track-to-track seek: 0  # milliseconds
drivedata: 0

8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 35843670        0    unused        0     0         # (Cyl.    0 - 92619*)
  e:  2097152        0     vinum                        # (Cyl.    0 - 5418*)
  f: 33746518  2097152     vinum                        # (Cyl. 5418*- 92619*)

How-To-Repeat: dd if=/dev/zero of=/dev/da0e count=1024