re: Modules loading modules?

[Paul Goyette <paul%whooppee.com@localhost>]

On Mon, 26 Jul 2010, matthew green wrote:

> it seems to me the root problem is that module_mutex is held while
> calling into the module startup routines.
>
> thus, the right solution is to remove this requirement.

Yes, that's what is needed.

But it sounds a lot simpler than it is.  Among other issues, we'd need 
to ensure that we continue to detect circular dependencies between both 
sets of required modules.  And, since we call the module startup routine 
for a required module _before_ we call it for the required module, we 
would need to release and then reacquire the mutex, all the while being 
sure that the data structures don't get changed out from under us.

We would end up with something like this sequence,where module A 
requires A1 and A2, and module B requires B1 and B2, and hopefully 
(B1 != A && B2 != A) (which would be a hidden circular dependency).

        mutex_enter()
        load module A
                load required module A1
                        mutex_exit()
                        call A1's init routine
                        mutex_enter()
                load required module A2
                        mutex_exit()
                        call A2's init routine
                                mutex_enter()
                                load module B
                                        load required module B1
                                                mutex_exit()
                                                call B1's init routine
                                                mutex_enter()
                                        load required module B2
                                                mutex_exit()
                                                call B2's init routine
                                                mutex_enter()
                                        mutex_exit()
                                        call B's init routine
                                        mutex_enter()
                                mutex_exit()
                        mutex_enter()
                mutex_exit()
                call A's init routine
                mutex_enter()
        mutex_exit()



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