Ok. This patch is technically safe because none of the touched
code can live in a module and so we never touch the exit code path.
However in the general case and as a code idiom this __net_initdata
on struct pernet_operations is fundamentally horribly broken.
Look at what happens if we use this idiom in module. There
is only one definition of __initdata ".init.data". The module
loader places all sections that begin with .init in a region of
memory that will be discarded after module initialization.
So in register_pernet_operations we pass in the a pointer to struct
pernet_operations and call the init method. Later when we remove the
module we again pass in the pointer to struct pernet_operations which
lived in an init section so it has been discarded. We dereference
that pointer to find the exit method and KABOOM!!!!
So I'm still opposed to __net_initdata on the grounds that at best
it is like putting our head under a guillotine and reaching up and
sawing at the row that holds the blade up with a pocket knife. It is
a think rope and a puny knife so you are safe for a while....
Eric
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