[openib-general] [KDAPL] module initialization order (was Re: [PATCH] kDAPL: remove typedef DAT_PROVIDER)

[Grant Grundler]

On Tue, May 10, 2005 at 01:20:49PM -0400, James Lentini wrote:
> 
> After reading through the kernel sources, I believe that builtin 
> module initialization functions are called by the do_initcalls 
> function in init/main.c.

correct

> I haven't conclusively determined how the initialization order is 
> specified. From what I've gleamed from mailing list archives, the 
> module initialization order was determined by link order.

There are several "classes" of init modules that dictate
a coarse level of ordering inside the list of init routines.
See the list of *_initcall() macros in include/linux/init.h.

> As a result 
> the relative position of the obj-$(CONFIG_XXX) lines in Makefiles 
> determined the order of module initialization. Often when I found 
> discussion of this topic, it was in the context of changing this 
> scheme to make the initialization dependencies explicit. However, it 
> does not appear that this was ever done.
> 
> One final piece of information that I came across is that the order of 
> initialization functions in the System.map file is the order that they 
> will be called in.

yup - but it's very arch specific and compile option specific
as to what the final order will be. If there is a strong dependency
within a class, one can fix this by directly calling the init routine
of the module is needed by another module. A (bad) example might be
suckyio^Wsuperio support on parisc platforms.

> Can anyone confirm any of the information above?

hth,
grant