Messages in this thread | | | From | Rusty Russell <> | Subject | Re: module_put_and_exit() and free_module() | Date | Wed, 09 Sep 2015 04:13:26 +0930 |
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Aleksa Sarai <cyphar@cyphar.com> writes: >>From my understanding, module_put_and_exit() can be used inside a > module to (from within the module) kill itself. However, it doesn't > seem to properly free the modules references (and internal > bookkeeping) since module_put_and_exit() doesn't call free_module(). > And attempting to remove the module after loading it and it running > module_put_and_exit() causes any attempt to remove the module to fail > with EBUSY.
It's not a general mechanism! It's for kernel threads which want to decrement module use counts as they exit: if they did this in the module there would be a moment where they are still running but the module could be unloaded.
> Am I missing something here? Is the purpose of module_put_and_exit() > different, or does module_put() cause the module references to get > reaped later? If that's the case, why do you get EBUSY when trying to > remove the module (surely you should get an ENOENT)? Is it even safe > to attempt to remove a module from within itself?
module_put() simply controls the reference count. Module removal only succeeds if the reference count is 0.
I would guess that you called module_put_and_exit() without a thread, and oopsed.
Cheers, Rusty.
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