Re: [RFC] Migrating net/sched to new module interface

[Werner Almesberger <wa@almesberger.net>]

Roman Zippel wrote:
> >  - prepare_deregister (like "deregister", but reversible)
> >  - commit_deregister
> >  - undo_deregister
> 
> You can simplify this. All you need are the following simple functions:
> 
> - void register();
> - void unregister();
> - int is_registered();
> - void inc_usecount();
> - void dec_usecount();
> - int get_usecount();

I'm not sure if you, you're not changing the semantics. What I was
describing was a non-blocking interface, e.g.

	if (!prepare_deregister(foo))
		return -E...;
	if (!prepare_deregister(bar)) {
		undo_deregister(foo);
		return -E...;
	}
	commit_deregister(foo);
	commit_deregister(bar);
	return 0;

With your interface, you're not guaranteed that you can re-register.
Well, you could externalize this, e.g. with

	int error = 0;

	inc_usecount(foo);
	inc_usecount(bar);
	unregister(foo); /* does nothing irrevokable since use count > 0 */
	unregister(bar);
	if (get_usecount(foo) > 1 || get_usecount(bar) > 1) {
		register(foo); /* re-registers foo */
		register(bar); /* re-registers bar */
		error = E...;
	}
	dec_usecount(foo);
	dec_usecount(bar);
	return error;

Is that what you had in mind ?

- Werner

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 / Werner Almesberger, Buenos Aires, Argentina         wa@almesberger.net /
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