Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Daniel Eisenbud]

I asked this in linuxppc-user bothj yesterday and months ago, and have
not received any replies, which made me wonder if this list would be a
better place to ask.  I haven't done any significant kernel hacking, but
know C well and am more than happy to try to debug and see if I can fix
this, but I'm not sure where to start.  I guess the first thing to do
should be to boot from a disk on the other SCSI bus and see what errors
I get from mesh, since right now everything just freezes hard without
any visible diagnostics.  Or is there a way, even with a totally frozen
SCSI bus (containing the swap partition among other things, though I can
of course swapoff before testing this) to tell anything useful about the
state of the machine once SCSI is frozen.  I have vaguely heard of, but
don't know the details of this "magic sysrq" thing.  Would that be
useful?

Please excuse my cluelessness -- any advice that people have is much
appreciated!

The text of my original message with the details of the problem is
below.

Thanks,
Daniel Eisenbud

----- Forwarded message from Daniel Eisenbud <eisenbud@cs.swarthmore.edu> -----

Date: Wed, 24 Jan 2001 22:28:54 -0500
From: Daniel Eisenbud <eisenbud@cs.swarthmore.edu>
To: linuxppc-user@lists.linuxppc.org
Subject: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode


I have a Powermac 7500 (with a G3 accelerator.)  I have replaced the
internal CD-ROM with a Yamaha CD-RW drive.  This sits on the mesh SCSI
bus.  I have the mesh driver configured to run at 5 megabytes/second
(since I get massive SCSI problems all over the place if I set it to
10.)  Under a variety of kernels, from 2.2.15 or so to 2.4.0 from Paul
Mackeras's tree, my SCSI setup is generally stable and I can burn CD-R
disks just fine in track-at-once mode.  However, if I try to burn a disk
in disk-at-once mode, either with cdrdao or cdrecord, the SCSI bus
appears to silently lock up hard, bringing down my whole machine.
Nothing is logged at all, as far as I can tell.  Has anyone had this
problem before?  Does anyone know of a solution?  If not, how would I go
about debugging this further?

Thanks in advance,
Daniel Eisenbud

--
Daniel E. Eisenbud
eisenbud@cs.swarthmore.edu




----- End forwarded message -----

--
Daniel E. Eisenbud
eisenbud@cs.swarthmore.edu

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Re: Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Benjamin Herrenschmidt]

>I have a Powermac 7500 (with a G3 accelerator.)  I have replaced the
>internal CD-ROM with a Yamaha CD-RW drive.  This sits on the mesh SCSI
>bus.  I have the mesh driver configured to run at 5 megabytes/second
>(since I get massive SCSI problems all over the place if I set it to
>10.)  Under a variety of kernels, from 2.2.15 or so to 2.4.0 from Paul
>Mackeras's tree, my SCSI setup is generally stable and I can burn CD-R
>disks just fine in track-at-once mode.  However, if I try to burn a disk
>in disk-at-once mode, either with cdrdao or cdrecord, the SCSI bus
>appears to silently lock up hard, bringing down my whole machine.
>Nothing is logged at all, as far as I can tell.  Has anyone had this
>problem before?  Does anyone know of a solution?  If not, how would I go
>about debugging this further?

Do you see any kind of kernel error messages on the console before it
locks up ?

Ben.


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Re: Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Daniel Eisenbud]

on Fri, Jan 26, 2001 at 12:07:24PM +0100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >I have a Powermac 7500 (with a G3 accelerator.)  I have replaced the
> >internal CD-ROM with a Yamaha CD-RW drive.  This sits on the mesh SCSI
> >bus.  I have the mesh driver configured to run at 5 megabytes/second
> >(since I get massive SCSI problems all over the place if I set it to
> >10.)  Under a variety of kernels, from 2.2.15 or so to 2.4.0 from Paul
> >Mackeras's tree, my SCSI setup is generally stable and I can burn CD-R
> >disks just fine in track-at-once mode.  However, if I try to burn a disk
> >in disk-at-once mode, either with cdrdao or cdrecord, the SCSI bus
> >appears to silently lock up hard, bringing down my whole machine.
> >Nothing is logged at all, as far as I can tell.  Has anyone had this
> >problem before?  Does anyone know of a solution?  If not, how would I go
> >about debugging this further?
>
> Do you see any kind of kernel error messages on the console before it
> locks up ?

Nope, nothing at all.  :-(  It just freezes.  Since the SCSI bus is
gone, any attempts to write to logs fail, as do any attempts to read
them, of course.  cdrdao gets to the "calibrating power" stage, the
light on the cd-rw drive blinks for a few seconds, and that's it.   Last
time I tried this experiment, I at least turned swap off first, and the
system survived a bit longer, but I wasn't able to find anything out.
Is there any other way to probe what's going on?  I do have a 2 gigabyte
drive that I could attach to the external SCSI bus and boot from: maybe
then I could get more info, at least, about what is going on.

-Daniel

--
Daniel E. Eisenbud
eisenbud@cs.swarthmore.edu

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Re: Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Benjamin Herrenschmidt]

>
>Nope, nothing at all.  :-(  It just freezes.  Since the SCSI bus is
>gone, any attempts to write to logs fail, as do any attempts to read
>them, of course.  cdrdao gets to the "calibrating power" stage, the
>light on the cd-rw drive blinks for a few seconds, and that's it.   Last
>time I tried this experiment, I at least turned swap off first, and the
>system survived a bit longer, but I wasn't able to find anything out.
>Is there any other way to probe what's going on?  I do have a 2 gigabyte
>drive that I could attach to the external SCSI bus and boot from: maybe
>then I could get more info, at least, about what is going on.

Do you get the same lockup without the G3 accelerator ?

Ben.

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Re: Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Daniel Eisenbud]

On Sat, Jan 27, 2001 at 12:39:31PM +0100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> Do you get the same lockup without the G3 accelerator ?

Good question.  I got the CD-RW and the accelerator at the same time,
so I actually have no idea.  About six months ago when I made a brief
attempt to look into this problem, I found another report of the same
thing, which I don't think mentioned an accelerator.  I'll have to try
to figure out where I saw that.  In any case, I can swap in the old CPU
this weekend and see if it works.  I'll report back when I have more
information.

-Daniel

--
Daniel E. Eisenbud
eisenbud@cs.swarthmore.edu

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Re: Fwd: mesh SCSI bus locks hard on 7500 when burning a CD-R in dao mode

[Daniel Eisenbud]

On Sat, Jan 27, 2001 at 02:57:58PM -0500, Daniel Eisenbud <eisenbud@cs.swarthmore.edu> wrote:
> On Sat, Jan 27, 2001 at 12:39:31PM +0100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> > Do you get the same lockup without the G3 accelerator ?
>
> Good question.  I got the CD-RW and the accelerator at the same time,
> so I actually have no idea.  About six months ago when I made a brief
> attempt to look into this problem, I found another report of the same
> thing, which I don't think mentioned an accelerator.  I'll have to try
> to figure out where I saw that.  In any case, I can swap in the old CPU
> this weekend and see if it works.  I'll report back when I have more
> information.

I just tried this without the G3, and the exact same thing happens.  I
also did "dmesg -n 8" on the console where I tried to run cdrdao, before
burning the CD, but got no additional output.  I'll try this again both
with cdrecord (which had the same failure mode the last time I was
trying to solve this problem) and with syslog logging only to the
console.  If those don't work, I guess the next step is probably to see
if I can see anything over a serial console, and maybe to install
another copy of the OS on the external hard disk and boot from there,
and see if that lets me get more information?

-Daniel

--
Daniel E. Eisenbud
eisenbud@cs.swarthmore.edu

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