sym53c875: reading /proc causes SCSI parity error

["Matthias Benkmann" <matthias@winterdrache.de>]

I have a reproducible problem that somehow reading from /proc causes a 
SCSI parity error.

When I am inside a chroot environment (on my IDE hard disk) with proc 
mounted on /proc and execute the following script from / (of chroot)

-----------------------
#!/bin/sh

case "z$1" in
  z) echo Finding
     find . -path "./old-distro" -prune -or -path "./static" -prune -or -
path "./usr/src" -prune -or -type f -exec $0 {} \;
     ;;
  *) strings $1 | grep -q /static || exit 0
     echo '*************'$1'****************'
     strings $1 | grep -A 3 -B 3 /static
     ;;
esac

exit 0
----------------------

and then (not concurrently, can be a minute later) access my SCSI hard 
disk, I get

sym53c875-0: SCSI parity error detected: SCR1=132 DBC=1e000000 SBCL=26
sym53c875-0: restart (scsi reset).
sym53c875-0: Downloading SCSI SCRIPTS.


When I access my SCSI hard disk first and use the script afterwards (again 
there can be some time in between), I get

sym53c875-0: SCSI parity error detected: SCR1=132 DBC=50000000 SBCL=0
sym53c875-0: SCSI parity error detected: SCR1=132 DBC=870b0000 SBCL=0
sym53c875-0:0: ERROR (81:0) (8-0-0) (f/95) @ (script 28:f31c0004).
sym53c875-0: script cmd = e21c0004
sym53c875-0: regdump: da 00 00 95 47 0f 00 0f 35 08 80 00 80 00 0f 02.
sym53c875-0: restart (scsi reset).
sym53c875-0: Downloading SCSI SCRIPTS.


I can repeat this as often as I want. The errors stop occuring when I 
unmount /proc (inside chroot). I can only guess that somehow reading from 
/proc (note that I forgot to prune /proc in the find command) causes the 
error. Are there some files in /proc that are not safe for reading?
And why does it only occur in chroot?

The error occurs with my normal 2.2.17 kernel and with the 2.4.12-ac3 
kernel. I have a Tekram DC 390U SCSI controller.

MSB

Linux version 2.2.17 (root@(none)) (gcc version 2.95.2 19991024 (release)) 
#1 Fri Feb 2 14:06:58 CET 2001
Detected 501122 kHz processor.
Console: colour VGA+ 80x25
Calibrating delay loop... 999.42 BogoMIPS
Memory: 257900k/262128k available (940k kernel code, 412k reserved, 2808k 
data, 68k init)
Dentry hash table entries: 32768 (order 6, 256k)
Buffer cache hash table entries: 262144 (order 8, 1024k)
Page cache hash table entries: 65536 (order 6, 256k)
CPU: L1 I Cache: 32K  L1 D Cache: 32K
CPU: AMD-K6(tm) 3D processor stepping 0c
Checking 386/387 coupling... OK, FPU using exception 16 error reporting.
Checking 'hlt' instruction... OK.
POSIX conformance testing by UNIFIX
mtrr: v1.35a (19990819) Richard Gooch (rgooch@atnf.csiro.au)
PCI: PCI BIOS revision 2.10 entry at 0xf0720
PCI: Using configuration type 1
PCI: Probing PCI hardware
Linux NET4.0 for Linux 2.2
Based upon Swansea University Computer Society NET3.039
NET4: Unix domain sockets 1.0 for Linux NET4.0.
NET4: Linux TCP/IP 1.0 for NET4.0
IP Protocols: ICMP, UDP, TCP
TCP: Hash tables configured (ehash 262144 bhash 65536)
Starting kswapd v 1.5 
Serial driver version 4.27 with no serial options enabled
ttyS00 at 0x03f8 (irq = 4) is a 16550A
ttyS01 at 0x02f8 (irq = 3) is a 16550A
es1370: version v0.31 time 14:08:53 Feb  2 2001
es1370: found adapter at io 0xd800 irq 15
es1370: features: joystick off, line in, mic impedance 0
RAM disk driver initialized:  16 RAM disks of 4096K size
loop: registered device at major 7
Uniform Multi-Platform E-IDE driver Revision: 6.30
ide: Assuming 33MHz system bus speed for PIO modes; override with 
idebus=xx
ALI15X3: IDE controller on PCI bus 00 dev 78
ALI15X3: chipset revision 193
ALI15X3: not 100% native mode: will probe irqs later
    ide0: BM-DMA at 0xb800-0xb807, BIOS settings: hda:DMA, hdb:pio
ALI15X3: simplex device:  DMA disabled
ide1: ALI15X3 Bus-Master DMA disabled (BIOS)
hda: ST340823A, ATA DISK drive
ide: Assuming 33MHz system bus speed for PIO modes; override with 
idebus=xx
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: ST340823A, 38166MB w/512kB Cache, CHS=4865/255/63, UDMA(33)
Floppy drive(s): fd0 is 1.44M
FDC 0 is a post-1991 82077
sym53c8xx: at PCI bus 0, device 10, function 0
sym53c8xx: setting PCI_COMMAND_PARITY...(fix-up)
sym53c8xx: 53c875 detected with Tekram NVRAM
sym53c875-0: rev=0x03, base=0xd6000000, io_port=0xd400, irq=12
sym53c875-0: Tekram format NVRAM, ID 7, Fast-20, Parity Checking
sym53c875-0: on-chip RAM at 0xd5800000
sym53c875-0: restart (scsi reset).
sym53c875-0: Downloading SCSI SCRIPTS.
scsi0 : sym53c8xx - version 1.3g
scsi : 1 host.
  Vendor: IBM       Model: DDRS-34560        Rev: S97B
  Type:   Direct-Access                      ANSI SCSI revision: 02
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
  Vendor: FUJITSU   Model: M2513E            Rev: 0040
  Type:   Optical Device                     ANSI SCSI revision: 02
Detected scsi removable disk sdb at scsi0, channel 0, id 1, lun 0
  Vendor: TEAC      Model: CD-ROM CD-532S    Rev: 1.0A
  Type:   CD-ROM                             ANSI SCSI revision: 02
Detected scsi CD-ROM sr0 at scsi0, channel 0, id 3, lun 0
sym53c875-0-<0,0>: tagged command queue depth set to 8
scsi : detected 1 SCSI cdrom 2 SCSI disks total.
sym53c875-0-<3,*>: FAST-20 SCSI 20.0 MB/s (50 ns, offset 16)
sr0: scsi3-mmc drive: 0x/0x caddy
Uniform CD-ROM driver Revision: 3.11
sym53c875-0-<0,*>: FAST-20 SCSI 20.0 MB/s (50 ns, offset 15)
SCSI device sda: hdwr sector= 512 bytes. Sectors= 8925000 [4357 MB] [4.4 
GB]
sym53c875-0-<1,*>: FAST-10 SCSI 10.0 MB/s (100 ns, offset 15)
sdb : READ CAPACITY failed.
sdb : status = 1, message = 00, host = 0, driver = 28 
sdb : extended sense code = 2 
sdb : block size assumed to be 512 bytes, disk size 1GB.  
ne2k-pci.c:vpre-1.00e 5/27/99 D. Becker/P. Gortmaker 
http://cesdis.gsfc.nasa.gov/linux/drivers/ne2k-pci.html
ne2k-pci.c: PCI NE2000 clone 'RealTek RTL-8029' at I/O 0xd000, IRQ 10.
eth0: RealTek RTL-8029 found at 0xd000, IRQ 10, 00:00:21:C6:1E:30.
Partition check:
 sda: sda1 sda2 < sda5 sda6 sda7 >
 sdb:scsidisk I/O error: dev 08:10, sector 0
 unable to read partition table
 hda: hda1 hda2
VFS: Mounted root (ext2 filesystem) readonly.
Freeing unused kernel memory: 68k freed
Adding Swap: 72256k swap-space (priority -1)
strings uses obsolete /proc/pci interface



----
Indecision is the key to flexibility.