order of executing MOD_LOAD and registering module sysctl-s

From: Andriy Gapon <avg_at_FreeBSD.org>
Date: Wed, 2 Aug 2017 13:13:11 +0300
As far as I understand a module initialization routine is executed via the
sysinit mechanism.  Specifically, module_register_init is set up as the sysinit
function for every module and it calls MOD_EVENT(mod, MOD_LOAD) to invoke the
module event handler.

In linker_load_file() I see the following code:
                        linker_file_register_sysctls(lf);
                        linker_file_sysinit(lf);

I think that this means that any statically declared sysctl-s in the module
would be registered before the module receives the MOD_LOAD event.
It's possible that some of the sysctl-s could have procedures as handlers and
they might access data that is supposed to be initialized by the module event
handler.

So, for example, running sysctl -a at just the right moment during the loading
of a module might end up in an expected behavior (including a crash).

Is my interpretation of how the code works correct?
Can the order of linker_file_sysinit and linker_file_register_sysctls be changed
without a great risk?

Thank you!

P.S.
The same applies to:
                linker_file_sysuninit(file);
                linker_file_unregister_sysctls(file);

-- 
Andriy Gapon
Received on Wed Aug 02 2017 - 08:14:11 UTC

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