Re: Read from CD-Rom -> crash

Ulrich Windl (Ulrich.Windl@rz.uni-regensburg.de)
Tue, 28 May 1996 09:26:27 +0200


On 27 May 96 at 20:31, Andries.Brouwer@cwi.nl wrote:

> Thomas Niederreiter:
>
> : there is a quite critical bug in the CD-Rom-Code which caused for me
> : some extreme heavy crashes. (Reset-Button only)
>
> : The last 4 blocks (each 2048 bytes) can't be read in most cases.
> : And here on kernel pre2.0.7 this causes the total blackout.
> : 1.3.98 just reports a lot of sense-errors but recovers.
>
> Yes. The (or at least a) problem is the read-ahead.
>
> The SCSI (and other) drivers cannot handle hardware problems -
> things used to be worse, but we are still very far from
> a satisfactory situation.
> This means that if the kernel tries to do readahead past
> the end of the CD, it may crash, or get into a "resetting for
> second half of retries ..." syndrome. Unpleasantness.
>
> You can set readahead to 0 using the small "raset" utility
> below, and this at least allows one to read the last few
> blocks on the CD.
>
> What really has to be done is to keep the information that
> a request is not from the user but is readahead invented by the
> kernel, so that no resetting and retrying is attempted when
> readahead fails. I have some patches, but I think it would be
> inappropriate to make radical changes in the SCSI code just
> before 2.0.

But also, crashes with 2.0 are not satisfying...

>
> Andries
Ulrich