Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1221038 > unrolled thread

Re: module_put_and_exit() and free_module()

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: module_put_and_exit() and free_module() Rusty Russell <rusty@rustcorp.com.au> - 2015-09-08 20:50 +0200

#1221038 — Re: module_put_and_exit() and free_module()

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [standalone]

Back to top | Article view | linux.kernel

csiph-web