Read from CD-Rom -> crash

Thomas Niederreiter (tn@bv.rz.fh-muenchen.de)
Sat, 25 May 1996 17:47:09 +0200 (MET DST)


Hi,

there is a quite critical bug in the CD-Rom-Code which caused for me
some extreme heavy crashes. (Reset-Button only)

Some people already reported that a CD with errors causes some
problems...As far I know Linus fixed this a little with pre.2.0.7.
Well this doesn't work for CD-Recordables.
A CD-Recordable written under Linux works well, except you want to read
the last few sectors. (e.g. when copying this CD).

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.

I know that these 4 blocks are written on CD-R. (I can get the exact
number of blocks on a CD from the ISO9660-Header).

This problem seems to have been always in linux , because the
cdwrite-2.0 manpage reports:

-P, --pad
Add 30 kilobytes (15 sectors) of nulls to the end
of each data track. This is a workaround for a bug
in Linux up to and including at least version
1.2.8, which would at times not correctly read the
last few sectors written. This option has no
effect on audio tracks.

Well...not only 1.2.8 it seems.

I hope anybody can find the error and fix it.

I tested this only with SCSI-CD-Roms. (Don't have others)

Thanx,

Thomas Niederreiter

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