Messages in this thread |  | | Date | Fri, 13 Sep 2002 10:18:51 +0200 | From | Helge Hafting <> | Subject | Re: [RFC] Raceless module interface |
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Rusty Russell wrote: > > In message <20020912030933.A13608@kushida.apsleyroad.org> you write: > > I don't see the point in this at all. > > Yes, I'm starting to realize that. > > Frankly, I'm sick of pointing out the same problems individually to > every shallow thinker who thinks that "it's easy". > > The fundamental problems with modules are as follows: > A) Many places in the kernel do not increment module reference counts > for you, and it is difficult currently write a module which safely > looks after its own reference counts (see > net/ipv4/netfilter/ip_conntrack_core.c's ip_conntrack_cleanup())
This sort of thing makes correct unloading hard, but in my eyes it is an argument for changing the module interface to something better and say "that thing CAN'T be a module of its own!"
What if we *require* modules to use some open/close reference count that don't change so often as to be a performance problem?
It makes the unloading/reloading problem easier, similiar to mount/umount.
It'll work for lots of modules, such as: * drivers for hardware devices, char, block, and NIC. * filesystems
Things with no easy refcounting (and it cannot even be grafted on) will have to be non-modular, or folded into some parent module.
Maybe IP connection tracking can't be modular with these rules - so what? Make it compiled-in, or a part of the IPV4-module. So if you really need to load and unload that you unload the ipv4_with_conntrack module and then load a ipv4_without_conntrack module.
To me, it seems like the current module interface is too fine-grained, and that cause trouble. I.e. the overhead of correct refcounting is so high in some cases that it isn't used - causing trouble with safe unloading. The solution is to say no to such modules. Making them work isn't easy - but why try?
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