From: Paul Gortmaker <paul.gortma...@windriver.com> Date: Sat, 20 Apr 2019 23:29:41 -0400
> People can embed modular includes and modular exit functions into code > that never use any of it, and they won't get any errors or warnings. > > Using modular infrastructure in non-modules might seem harmless, but some > of the downfalls this leads to are: > > (1) it is easy to accidentally write unused module_exit removal code > (2) it can be misleading when reading the source, thinking a driver can > be modular when the Makefile and/or Kconfig prohibit it > (3) an unused include of the module.h header file will in turn > include nearly everything else; adding a lot to CPP overhead. > (4) it gets copied/replicated into other drivers and spreads quickly. > > As a data point for #3 above, an empty C file that just includes the > module.h header generates over 750kB of CPP output. Repeating the same > experiment with init.h and the result is less than 12kB; with export.h > it is only about 1/2kB; with both it still is less than 12kB. One driver > in this series gets the module.h ---> init.h+export.h conversion. > > Worse, are headers in include/linux that in turn include <linux/module.h> > as they can impact a whole fleet of drivers, or a whole subsystem, so > special care should be used in order to avoid that. Such headers should > only include what they need to be stand-alone; they should not be trying > to anticipate the various header needs of their possible end users. > > In this series, four include/linux headers have module.h removed from > them because they don't strictly need it. Then three chunks of net > related code have modular infrastructure that isn't used, removed. > > There are no runtime changes, so the biggest risk is a genuine consumer > of module.h content relying on implicitly getting it from one of the > include/linux instances removed here - thus resulting in a build fail. > > With that in mind, allmodconfig build testing was done on x86-64, arm64, > x86-32, arm. powerpc, and mips on linux-next (and hence net-next). Series applied, thanks Paul.
