Messages in this thread | | | Date | Thu, 13 Jan 2000 10:20:17 +0000 (GMT) | From | Tigran Aivazian <> | Subject | Re: [idea] request_module(const char *fmt, ...); |
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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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