Date: Sat, 22 Apr 1995 22:01:21 -0700 (PDT) From: Julian Elischer <julian@ref.tfs.com> To: ponds!rivers@dg-rtp.dg.com (Thomas David Rivers) Cc: freebsd-hackers@freefall.cdrom.com Subject: Re: Interesting SCSI cdrom problem.. Message-ID: <199504230501.WAA25757@ref.tfs.com> In-Reply-To: <199504230228.WAA28254@lakes> from "Thomas David Rivers" at Apr 22, 95 10:28:14 pm
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>
This is a 'feature' of the driver
once the door has been openned, the drive reports to the driver, that
there has been user intervention of some kind..
specifically a 'Unit attention' erro is reported to the driver..
this tells the driver that the cdrom MAY HAVE BEEN CHANGED!.
The driver therefore aborts ALL operations until ALL USERS have closed the
device. (including the 'mount' 'user' ).
When the last user has closed the device, operations on the cdrom are
re-enabled..
I'm glad to see you are getting this as it proves that the code in
question is working, and it is vitally important to devices
with read-write removable media that it does....
consider..
async write to drive...
{change media}
sync
(OUCH!)
the same problem exists for cdoms but it doesn't corrupt the media,
just totally screws the internal cached copy of the filesystem nodes
(i.e if it assumed that the same cdrom was in but wasn't.....)
>
> I have a NEC 3xP - which is/was their "personal" SCSI CD-ROM.
>
> It's nice enough and seems fast...
>
> However, I notice that when the disk spins down; from lack of an
> access in a few minutes; there doesn't seem to be anything I can
> do to spin it up again, except to umount the drive and re-mount it.
>
> Or - it's possible that the scenario is that if I mount the drive,
> then open the door (which you have to do so see if the drive is spinning)
> then re-close the door - that resets the drive, but isn't reflected
> in the "mount".
>
> What usually happens is that future accesses to the files (unless
> they were cached) causes I/O errors.
>
>
> (Well - I think I've empirically determined it's situation #2 - if you
> leave the CD in the drive, and wait - the drive does spin down. As long
> as you don't open the drive door, everything is fine. If you open,
> then close, the drive door - the mount is still present, and you get I/O
> errors.)
>
> - Dave Rivers -
>
>
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