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Date:      Wed, 5 Jun 1996 22:09:46 -0700
From:      Deborah Gronke Bennett <deborah@microunity.com>
To:        FreeBSD-gnats-submit@freebsd.org
Subject:   kern/1296: BUS DEVICE RESET and machine crash with Adaptec 2940 Ultra
Message-ID:  <199606060509.WAA03841@traken.microunity.com>
Resent-Message-ID: <199606060520.WAA03923@freefall.freebsd.org>

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>Number:         1296
>Category:       kern
>Synopsis:       BUS DEVICE RESET and machine crash with Adaptec 2940 Ultra
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jun  5 22:20:01 PDT 1996
>Last-Modified:
>Originator:     Deborah Gronke Bennett
>Organization:
MicroUnity Systems Engineering, Inc.
>Release:        FreeBSD 2.1-STABLE i386
>Environment:

	(this is an extract of the dmesg output from the machine)
	(This machine is a Pentium P-166)
	chip0 <Intel 82437 (Triton)> rev 2 on pci0:0
	chip1 <Intel 82371 (Triton)> rev 2 on pci0:7
	ahc0 <Adaptec 2940 Ultra SCSI host adapter> rev 0 int a irq 11 on pci0:17
	ahc0: aic7870 Ultra Single Channel, SCSI Id=7, aic7870, 255 SCBs
	ahc0 waiting for scsi devices to settle
	(ahc0:0:0): "QUANTUM XP32151 1074" type 0 fixed SCSI 2
	sd0(ahc0:0:0): Direct-Access 2053MB (4205100 512 byte sectors)
	ahc0: target 4 requests 5.0MB/s transfers, but adapter in Ultra mode can only sy
	nc at 10MB/s or above
	ahc0:A:4: Warning - message rejected by target: 0x1
	(ahc0:4:0): "PLEXTOR CD-ROM PX-6XCS 1.02" type 5 removable SCSI 2
	cd0(ahc0:4:0): CD-ROM 
	cd0(ahc0:4:0): NOT READY asc:3a,0 Medium not present


>Description:

	The machine boots fine. When I attempt to mount the FreeBSD
	install disk from the CD-ROM drive, I see:
	ahc0: target 4, lun 0 (st0) timed out
	cd0(ahc0:4:0): BUS DEVICE RESET message queued
	and then after a moment,
	cd0(ahc0:6:0): Target Busy
	and then the machine locks up. I have booted
	a kernel with DDB enabled, but I cannot get into
	the debugger from this locked condition. I must reset
	or powercycle.

	Another user posted a message on the newsgroup
	comp.unix.bsd.freebsd.misc which appears to report
	a similar or the same problem:
	----begin extract of posting from Gunther Schadow (gusw@zedat.fu-berlin.de)
	my new machine has an Adaptech 2940 Ultra SCSI host adapter with
	an IBM DORS SCSI2 (2 GB) disk, a CD ROM and a DAT drive attached to
	it. Now, when I write to the DAT, everything seems O.K., however,
	when trying to read, I sometimes get:

	ahc0: target 6, lun 0 (st0) timed out
	st0(ahc0:6:0): BUS DEVICE RESET message queued
	and then:
	st0(ahc0:6:0): Target Busy

	I can't figure out, what is wrong here, since sometimes reading works
	just fine.

	But then, there's an other problem, that occurs even when writing to
	the DAT (namely a file system dump). Now, it's the disk that timed
	out, and this causes the SCSI bus to reset, and the kernel to hang,
	doing nothing any more.

	ahc0: target 0, lun 0 (sd0) timed out
	ad0(ahc:0:0:0): BUS DEVICE RESET message queued
	ahc0: target 0, lun 0 (sd0) timed out

	and HANG.
	---end extract of posting

>How-To-Repeat:

	See description.
	I first suspected a hardware problem with the CD or the
	CD-ROM drive, but I verified both of them on anther
	PC running the same release, but has a BusLogic SCSI
	controller. This and the other news posting leads
	me to believe that the adaptec controller is the
	common problem item.
	The same PC works fine with WindowsNT, so I would tend
	to believe that the controller itself is not broken, just
	has some problems with the FreeBSD driver.

>Fix:
	
	Do not use the CD-ROM drive with FreeBSD.
	A 2GB SCSI disk on the same controller chain seems
	to be working fine.

>Audit-Trail:
>Unformatted:



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