Re: (remove) event not supported.

[David Brownell <david-b@pacbell.net>]

> >It's not a reference count, since it doesn't address the case where
> >another module references it
> 
> It is a dynamic reference count.  The reference from another module is
> a static reference count.  Historical.

I see what you're saying, but that doesn't mean I'd then agree
to call it a "reference" count!


> >Since the counter can be (as
> >you highlighted!) updated at any time, there's nothing to make it
> >be a "reference" count.


> >      The networking framework is pretty explicit
> >that it must be used as an "open" count
> 
> If networking framework says that then it is wrong.
> 
> >(SET_MODULE_OWNER arranges this).
> 
> SET_MODULE_OWNER only exports the address of the module structure so
> external code can adjust the use count. 

When the interface is opened or closed ... and a few other
cases related to calling into the module.  (Related point:  I
suspect the USB code should do the same when it probes
drivers, to avoid those same races.)

From the perspective of a normal user, "lsmod" for net
drivers shows use count 0 when no interface exposed
by that driver is "up" (open).


>     Normally that is via the open
> routine, but file systems just do one MOD_INC_USE_COUNT in fs/super.c
> so it is a mount count, not an open count.  Some netfilter modules want
> to count the number of packets controlled by that module, again not an
> open count.

I'd argue those are all logically equivalent to "open":  dynamic
behavior (as you noted) that needs to prevent "rmmod".

One hopes that opening a block device like /dev/sda1 with
a user mode tool, rather than "mount", will prevent "rmmod"...

- Dave



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