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Date: Tue, 17 Sep 1996 19:13:16 -0700 (PDT)
Message-Id: <199609180213.TAA09645@silvia.HIP.Berkeley.EDU>
To: gibbs@freebsd.org
CC: scsi@freebsd.org
Subject: A couple of SCSI problems
From: asami@freebsd.org (Satoshi Asami)
Sender: owner-freebsd-scsi@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

Justin,

(1) A bus reset arriving at an unfortunate time can crash the system.
    This is what happened when I rebooted a machine connected to
    another via a 2-controller SCSI chain:

===
## gdb -k kernel.11 vmcore.11
GDB is free software and you are welcome to distribute copies of it
 under certain conditions; type "show copying" to see the conditions.
There is absolutely no warranty for GDB; type "show warranty" for details.
GDB 4.13 (i386-unknown-freebsd), 
Copyright 1994 Free Software Foundation, Inc...(no debugging symbols found)...
IdlePTD 201000
current pcb at 1e81f0
panic: %s: Timed-out command times out again

#0  0xf0113197 in boot ()
(kgdb) bt
#0  0xf0113197 in boot ()
#1  0xf0113456 in panic ()
#2  0xf01d82e5 in ahc_timeout ()
#3  0xf010b17c in softclock ()
#4  0xf01b5e0c in splz_swi ()
#5  0xf012d72f in biowait ()
#6  0xf012bb3f in bread ()
#7  0xf019bc45 in ffs_update ()
#8  0xf019f25c in ffs_fsync ()
#9  0xf019de90 in ffs_sync ()
#10 0xf01328bb in sync ()
#11 0xf011306d in boot ()
#12 0xf0113456 in panic ()
#13 0xf01d82e5 in ahc_timeout ()
#14 0xf010b17c in softclock ()
#15 0xf01b5d87 in doreti_swi ()
#16 0xcf985 in ?? ()
#17 0xd1ae3 in ?? ()
#18 0xd5249 in ?? ()
#19 0xd5076 in ?? ()
#20 0x2f538 in ?? ()
#21 0xa6e1 in ?? ()
#22 0x1571b in ?? ()
#23 0x2e93b in ?? ()
#24 0x30e26 in ?? ()
#25 0x107e in ?? ()
===

    The crashed system was running a single "make" on a 35-disk CCD.

(2) The ahc probe sometimes gets stuck right after it prints out
    "target foo refuses wide negotiation, using 8-bit transfers".
    This can happen for a variety of reasons, from loose cabling (on
    my home computer a while ago when the narrow SCSI connector on the
    CDROM was loose) to mystery (same symptom since last week, except
    the cable is not loose this time and I currently run the machine
    without CDROM) to bus resets.  About bus resets: as I wrote above,
    one of the machines crashed when the other sent a bus reset as
    part of the boot process -- well, the crashed machine in turn sent
    a bus reset, which screwed up the booting process of the other
    machine, which hung, printing out this message and some other
    stuff (mostly incoherent, like "size: 0MB").  There are no narrow
    SCSI devices on this system.  It booted fine when I power-cycled
    it.

    Whatever the reason, it seems like there is a minor race
    condition, as the symptom seems almost exactly like what used to
    happen before you came over to our lab and fixed a bug.

What do you think, Justin?

Satoshi