DVD players (hardware)

[Daniel Stonier]

On Mon, 28 Jun 2004 17:58:05 +0100, James Wilkinson  
<james at westexe.demon.co.uk> wrote:

> Daniel Stonier wrote:
>> I've been having problems lately with my dvd player - seems to be   
>> locking
>> up frequently on dvd's in a movie and repetitiously sitting in the one  
>> spot trying to read without success.Admittedly some   of the problems  
>> are due to dvd's with scratches, but it
>> seems to do it far more frequently now the player is getting a little    
>> aged.
>>
>> Anyway, my question is this - how do you kill it? Only way I know of
>> currently is to reboot the computer. Killing the process
>> often doesn't work and if it does occasionally, the dvd hardware itself
>> still keeps beating itself senseless.
>
> No-one seems to have answered this one, so I'll see what I can do.
>
> Firstly, you do know about kill -9, don't you? This will kill anything
> that can be killed.
>
> If that doesn't work, then the chances are that the process is in the
> middle of a system call (and is into kernel mode). When this happens, the
> signal is only acted upon when the system call returns. If you have
> suitably dodgy hardware (and it sounds like you do), the system call may
> not actually return.
>
> Note that this does not mean that the kernel freezes. When a synchronous
> call is made that requires a hard disk read, Linux expects to go away for
> at least 10 ms (more like 100 ms with a CD or DVD), and wait for the
> storage adapter to notify the kernel (with an IRQ and suitable messages:
> note that I'm assuming DMA).
>
> That's just what happens here. It's just that the DVD never returns the
> data, but doesn't return a read error, so the kernel remembers the
> outstanding request indefinitely.
>
> This is probably due to your DVD-ROM drive failing, although it could be
> an oddity of the IDE adapter. Do you find the same symptoms with
> CD-ROMs?  How about DVD-ROMs? (DVDs are a lot harder for a marginal
> DVD-ROM drive to read, but there's not much difference to the IDE side
> of things).
>
> HTH,
>
> James.
>

Thanks for the reply. Yes, kill -9 wasn't working and you were spot on
about the kernel behaviour. The rest of the system still operates fine -  
only
the process involved and the dvd player lock up.

I'm not sure if the same problem crops up with CD-ROMs. Haven't seen it,  
but
I haven't exactly thrashed the drive for very long with CD-ROMS to have  
seen it
yet either. This is only a recent problem with the DVD player so I dont  
think it is a
problem with anything else in the machine, probably just an aging player
that will need to be replaced.

Thanks,
Daniel.



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