Re: Synchronizing scsi_remove_host and the error handler

[James Bottomley <James.Bottomley@SteelEye.com>]

On Sun, 2005-08-07 at 10:59 -0400, Alan Stern wrote:
> What sort of synchronization is there between scsi_remove_host and the 
> error-handler thread?  Offhand I can see two possible problems, depending 
> on how the LLD is written:

There isn't any by design.

I think you're not thinking about how this works correctly.  What remove
host does is loop over the active devices removing them from visibility
and trying to do a final put on the generic devices before removing the
host from visibility and doing a final put on it.

However, any outstanding user will have a reference and will keep all
the bits of the hierarchy in place until that reference is relinquished.

> In general, there needs to be some way for the error handler to prevent
> the LLD from being unloaded.  I don't know what the best answer is.  Has
> anyone thought about this?

I take it the problem is that most LLDs go on to release resources (like
interrupts and memory regions) immediately after calling
scsi_remove_host()?

The solution is probably to trigger the resource cleanup from the host
device release method.

James