Re: unclean yanking out of device?

[linas@austin.ibm.com]

On Wed, Jan 14, 2004 at 02:19:21PM -0800, Greg KH wrote:
> On Wed, Jan 14, 2004 at 04:00:02PM -0600, linas@austin.ibm.com wrote:
> > 
> > What is supposed to happen if I just yank out a (network/scsi) device
> > while it is being used, without calling any of the hotplug unregister
> > remove etc. functions in advance?
> 
> Depends on the driver, device type, subsystem type, and most
> importantly, the kernel version (2.2?, 2.4?, 2.6?)
> 
> This is better asked on the linux-kernel mailing list, with a specific
> and detailed question, as you have asked a very broad one.

Sorry, this was intentionally a broad question; I'm hoping to hash
out a broad answer here before I go lkml.

Let me rephrase:  I want to make 'appropriate' changes to the 2.6/2.7
kernel, and some selected device drivers, so that a sysadmin can 
stupidly yank out an *ordinary* PCI card (not a pcmcia) without doing 
an orderly shutdown in advance.

More specifically, I have a whiz-bang PCI controller that will
shut down a PCI slot when it is hit by a cosmic ray (data/address 
parity error, other error, etc.).  I want to be able to "recover"
that slot, (if its recoverable), and get things going again.

I'm kind-of on day 2 of thinking about this problem, and as far
as I've gotten is thinking that some of the hot-plug infrastructure
might be useful in doing this.   I've also noticed that include/linux/pci.h
struct pci_driver doesn't have a "remove_because_your_hardware's_already_gone"
callback, and it seems to me that this kind of callback would be needed.

So I'm sort of trolling to find out if this kind of a problem
has been discussed before, and for other interested parties
to discuss it with.  

--linas

p.s. yes, I know the broad reprecussions something like this can have.
I have noticed, for instance, that if you unplug a hot scsi cable,
that reiserfs3 panic's, whereas ext3 seems to deal with it nicely.

I'm hoping to slowly start dealing with the broader implications ... 
eventually.


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