Now I found a reason why request_module() can *NOT* be a macro. Ever.
Because it wouldn't work for the calls like
(void) request_module("ide-blabla");
or
if (request_module("misc-blabla") == 0)
or some others you can easily imagine. It *worked* before only because all
the calls to request_module() were either surrounded by CONFIG_KMOD or
were in the form of a very simple:
request_module(modname);
So, having it as macro or not is not a matter of taste. Having it as a
macro is *wrong*. It is inconsistent, because it assumes the callers
surround their code with CONFIG_KMOD, but some (e.g. telephony) don't but
just use it in a "valid" way.
This time I cc'd Linus because this finding puts the last nail on the
coffin of the "we want macro and not a function" approach and therefore
proves the validity of my implementation (the patch I sent earlier):
http://www.ocston.org/~tigran/patches/kmod-2.3.40-p1.patch
Regards,
------
Tigran A. Aivazian | http://www.sco.com
Escalations Research Group | tel: +44-(0)1923-813796
Santa Cruz Operation Ltd | http://www.ocston.org/~tigran
On Wed, 12 Jan 2000, James Manning wrote:
> [ Wednesday, January 12, 2000 ] Tigran Aivazian wrote:
> > In cases where it adds substantial overhead
> > of re-walking through the entire list (e.g. get_fs_type which walks
> > through file_systems) the caller should (and does) check the return from
> > request_module() and only does the extra work if it is == 0.
>
> But the beauty of the macro method is that you have a much (relatively)
> smaller kernel as your preprocessor reduces the request_module to -EINVAL
> at compile-time and you get to let gcc optimize away (dump dead code :)
> the entire chunk of code... you've saved a branch, cache efficiency, etc..
>
> James
> --
> Miscellaneous Engineer --- IBM Netfinity Performance Development
>
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