PCI hotplug w/ drivers linked statically vs. module

PCI hotplug w/ drivers linked statically vs. module

[Stephen Cameron]

HI,

I noticed a difference in behavior with PCI hotplug, depending
on if the driver in questino is loaded as a module, or statically
linked.

For example, the tg3 driver, hot-unplugging, then hot-replugging
works seemingly well if the driver is a module, but differnetly (poorly?)
if it is statically linked. (eth0 disappears and does not come
back.)

Trying out the cciss driver (with some changes), we did get it to
hot-unplug and hot-replug while it was in use as md multipath
primary path (failed over to secondary path ok upon hot-unplug.)  
and then i/o was able to be done on the old card when the card was 
re-plugged.  This was with the driver linked as a module.
(BTW, how can you tell the md driver that a failed path
is now good again?)

However, if we linked statically, then we still get requests
coming into the driver after the hba[] structure is deallocated.
(resulting in a panic). This does not seem to happen if the driver 
is linked as a module.

Looking at the tg3 driver, it doesn't seem to take any precautions
in it's remove function.  (Maybe there are things in the upper layers
there for e.g. pcmcia, that make it work...)

Note, in no case that I can see is the modular driver _unloaded_.
(e.g. there are other same type  boards in the system which continue to
function after one board is hot-unplugged) 

So why the difference in behavior with PCI hotplug and drivers
linked statically vs. as a module?

Thanks,

-- steve

Re: PCI hotplug w/ drivers linked statically vs. module

[Greg KH]

On Fri, Mar 07, 2003 at 09:27:40AM +0600, Stephen Cameron wrote:
> 
> I noticed a difference in behavior with PCI hotplug, depending
> on if the driver in questino is loaded as a module, or statically
> linked.
> 
> For example, the tg3 driver, hot-unplugging, then hot-replugging
> works seemingly well if the driver is a module, but differnetly (poorly?)
> if it is statically linked. (eth0 disappears and does not come
> back.)

Is the tg3 driver's remove() function actually being called?  In looking
at the driver, the callback is declared properly, so it should be
present when building the driver into the kernel.

> So why the difference in behavior with PCI hotplug and drivers
> linked statically vs. as a module?

I have no idea right now, sorry.
Only thing I can think of is you have to mark the remove function as
"__devexit" and not "__exit" to make sure the function is really there
if CONFIG_HOTPLUG is enabled.

thanks,

greg k-h

RE: PCI hotplug w/ drivers linked statically vs. module

[Cameron, Steve]

I forgot to mention, this was with a 2.4.21-pre5 kernel
(plus a few changes) -- steve