[Re: [PATCH] mux-core: make it explicitly non-modular] On 09/03/2017 (Thu
13:01) Peter Rosin wrote:
> On 2017-03-09 10:39, Peter Rosin wrote:
>
> *snip* *snip*
>
> >> Per the above use case (minimal vmlinux) the unload isn't so important,
> >> and in many cases it may be racy or simply not make sense. If that is
> >> the case, you don't need to provide a module_exit, and in the past I
> >> think we used to bump the module use count at a successful load to
> >> prevent unloading ; there might be a more elegant method now; google is
> >> your friend here. Also, I don't think name reuse/confusion is an issue.
> >
> > Ok, I thought it all boiled down to making the mux-core Kconfig a tristate
> > option and changing subsys_initcall(...) to module_init(...).
> >
> > But if I do that, I cannot be sure that the mux-core has been initialized
> > before drivers and clients start to use it in the non-modular case (if
> > things are modules, the dependencies should ensure that the mux-core is
> > loaded/initialized before any users are loaded). But there is no
> > topological sorting going on for ordering init calls in the non-modular
> > case.
> >
> > In short, I get:
> >
> > WARNING: CPU: 0 PID: 1 at drivers/base/class.c:438:
> > class_find_device+0xac/0xb8
> > class_find_device called for class 'mux' before it was initialized
[...]
> >
> > So, it appears that I also have to determine if the core has been
> > initialized in all its entry points and return -EPROBE_DEFER (or something)
> > when not. I suppose I could instead initialize on-demand, but that seems
> > more difficult the do without races...
> >
> > Am I missing something?
>
> I did some digging and e.g. drivers/uwb was moved before drivers/usb in
> commit ae5d82cb8d60 ("uwb: build UWB before USB/WUSB") to resolve what
> appears to be a similar situation. I suppose I could just move mux up in
> drivers/Makefile so that it is before both i2c and iio.
So, you can "cheat" and leave it as subsys_initcall (and add a comment
why it is) and it will be subsys_initcall when built-in and module_init
when modular -- that should work too, and if you look around you'll
probably see many other existing instances of that going on.
init.h
#ifndef MODULE
[...]
#define subsys_initcall(fn) __define_initcall(fn, 4)
module.h
#else /* MODULE */
[...]
#define subsys_initcall(fn) module_init(fn)
Paul.
--
>
> Cheers,
> peda
>
