Messages in this thread | | | Date | Thu, 4 May 2006 12:50:55 -0400 | From | Wakko Warner <> | Subject | Re: cdrom: a dirty CD can freeze your system |
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Alan Cox wrote: > On Iau, 2006-05-04 at 14:32 +0200, Herbert Rosmanith wrote: > > I've been experimenting with damaged CDs this day. I observed that > > a dirty or (partly) unreadable CD will (1) block the process which is > > trying to read from the CD - it will be in state "D" - uninterruptible > > sleep and (2) sometimes(?) probably freeze your system such that even > > a manual reboot wont work (e.g., because it's not possible to log in, or > > keystrokes are no longer accepted) and a power-cycle is required. > > This is a known problem with the old IDE layer. There are several > problems involved > > 1. The old IDE layer reset confuses some drives fatally > 2. The DMA recovery tricks it does break the state machine of some > controllers and hang them for good > 3. The error recovery and timer code races and can hang > 4. The speed change paths used on DMA fail change down race everything > > > please tell me a way to savely > > (1) reset the IDE interface, e.g via IDE-TASKFILE (or, for testing, > > a sequence of outb() to the chip) > > (2) reset the CD-drive - sending a WIN_DEVICE_RESET (linux/hdreg.h line 196) > > doesnt seem to be enough. > > Please try the libata PATA patches instead of the old IDE layer.
I have noticed a problem which I believe is in sr_mod. Doesn't matter if the physical connection is ide, scsi, usb, etc.
If I access a drive that is not ready (ie, no disc, or in the process of loading in a disc), the drive will no longer function properly.
I'm not sure if I can explain it fully, and I'm not sure if it's already been reported.
I place a CD on the tray and do a mount. Mount will fail (lets just assume that under 2.4.x this worked). I eject the cd and reinsert and wait for it to become ready. Mount will still fail. Last I recall getblks ioctl returns 2 or 4 in this case. The only way to fix is to rmmod sr_mod and reinsert sr_mod.
another example would be that I insert a disc, say with 159000 sectors and I'm able to read from it just fine. I make the above mistake but I insert a disc with 200,000 sectors. The disc will be reported with 159000 instead of the correct 200,000 sectors and some files will not be readable. Again, rmmod and modprobe sr_mod fixes the problem.
I've been able to reproduce this on every linux system running 2.6 that I've used with a CDRom.
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