MOD_UNLOAD and driver with cdev

[Kostik Belousov]

On Wed, Jan 21, 2009 at 05:50:38PM +0200, Andriy Gapon wrote:
> on 21/01/2009 17:39 Kostik Belousov said the following:
> > On Wed, Jan 21, 2009 at 05:03:20PM +0200, Andriy Gapon wrote:
> >> Do I need to code for MOD_UNLOAD for driver module that also creates a cdev?
> >> I see in the current code that one strategy is to simply call
> >> destroy_dev(). I guess detach routines are called automatically and
> >> destroy_dev can be done there as well..
> > What are the detach routines ? Do you mean newbus device detach ?
> 
> Yes, device_detach. This seems to work and make_device_driver.sh also
> suggests it this way. But I am not sure about possible races.
> 
> > Yes, the usual strategy is to call destroy_dev from unload handler.
> > 
> >> Is it reasonable to refuse unload if cdev is in use (in MOD_QUIESCE)?
> >> How to check for that best?
> > 
> > This cannot be checked race-free.
> 
> So no point in trying?

I would say no. You could use count_dev(), but my own experience shown
that ability to unload driver is more important then unadvertently
knock out filedescriptor from under the running program.
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