Re: pcmcia: release_class patch concern

[Dmitry Torokhov <dtor_core@ameritech.net>]

On Tuesday 28 June 2005 01:14, Dominik Brodowski wrote:
> Hi Dmitry,
> 
> On Mon, Jun 27, 2005 at 11:56:49PM -0500, Dmitry Torokhov wrote:
> > Hi Dominik,
> > 
> > I noticed that Linus committed the patch from you that introduces waiting
> > for completion in module's exit routine. I believe it is a big no-no
> 
> Is it really? Any PCI driver which calls pci_unregister_driver() waits for
> completion (-> driver_unregister() -> wait_for_completion(&drv->unloaded) ).
>

Driver objects don't linger around - teardown is straightforward and
attribute access protected with bumping up module's reference count.
So it usually works out pretty well. 

> 
> > as something like this will wedge the kernel:
> > 
> > 	rmmod <module> < /sys/path/to/devices/attribute
> 
> Why would anybody issue such a command?

This is just the simpliest method to illustrate the problem. I am sure
someone could come up with a more realistic example. I think Al Viro
mentioned it some time ago, but I can't find his post...

> But it even wouldn't succeed, as 
> the module usage count would be >0 if there are attributes below
> /sys/class/pcmcia_socket/
...
> So I could have left the other wait_for_completion out, as it should never
> actually _wait_. Nonethteless, I consider it to be a safeguard.

Since the completion will never be actually used I'd rather not have it
at all - I believe it sets bad example.
 
-- 
Dmitry