[Bug 13345] New: panic when reading data from IDE CDROM with >= 2.6.29 kernels

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http://bugzilla.kernel.org/show_bug.cgi?id=13345

           Summary: panic when reading data from IDE CDROM with >= 2.6.29
                    kernels
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 2.6.30-rc5
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IDE
        AssignedTo: io_ide@kernel-bugs.osdl.org
        ReportedBy: modestas@vainius.eu
        Regression: Yes


Created an attachment (id=21439)
 --> (http://bugzilla.kernel.org/attachment.cgi?id=21439)
Backtrace of the OOPS with 2.6.30-rc5

Hello,

I get kernel panic when data is read from IDE CDROM with 2.6.29 or later
kernels (testing 2.6.30-rc5 at the moment). I have never had the issue with
2.6.28 and earlier kernels.

I suspect the cause though. My CD/DVD drive is pretty old and might be a bit
faulty (or this might kernel be misinterpreting my drive sometimes). <= 2.6.28
kernels used to turn off DMA due to seek errors (if I recall correctly)
sometimes. However, I used to be able to turn DMA back on with hdparm and I
have never really had read() failures. Now with >= 2.6.29 I have never seen DMA
being turn off on my CD/DVD drive but I guess kernel just panics instead. So I
suspect there is a regression in the latest kernels which triggers
unrecoverable panic instead of drive reset.

I got the attached backtrace (sorry, I couldn't do better than this picture)
with 2.6.30-rc5 on Debian unstable amd64 box while doing a simple:

$ dd if=/dev/cdrom of=/dev/null bs=1M

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