can not resolve global kernel variable.

[Eugene Goubine]

Hello , dear list users.
> From my module I am trying to register for the system suspend using
> the * 
register_pm_notifier(nb)*
which is expanded to *blocking_notifier_chain_register(&pm_chain_head, nb).*
**
I have a linker warning which tells "pm_chain_head" is undefined. I do
see  pm_chain_head in my /proc/kallsyms.
What do I miss? Thank you.

[Kyle McMartin]

On Tue, Feb 19, 2008 at 01:41:15PM +0200, Eugene Goubine wrote:
>  Hello , dear list users.
>  >From my module I am trying to register for the system suspend using the *
>  register_pm_notifier(nb)*
>  which is expanded to *blocking_notifier_chain_register(&pm_chain_head, nb).*
>  **
>  I have a linker warning which tells "pm_chain_head" is undefined. I do
>  see  pm_chain_head in my /proc/kallsyms.
>  What do I miss? Thank you. 
It's hard to comment on it if you don't attach the source code...

At a guess, you tried using register_pm_notifier, that failed to link,
so you tried to use the function that it calls, which won't work since
pm_chain_head is static to the kernel/power/main.c compilation unit.

License your module under the GPL and add MODULE_LICENSE("GPL") and
you'll be able to use the register_pm_notifier export...

regards, Kyle

[Eugene Goubine]

Kyle, thanks for reffering,but it seems like GPL is not the case.
I want to write a module to track netdevices present.
Sort of a protocol sitting there. It is GPL'ed, but register_pm_notifier
usage ( as you can see in sources)
gives linker warning "pm_chain_head undefined",since register_pm_notifier is
"static inline" and expanded
to blocking_notifier_chain_unregister(&pm_chain_head, nb).
Why do you say pm_chain_head is static there ? Is it because it is not
exported by EXPORT_SYMBOL ?
So what does it have to do with the license ( which is already GPL, but I
just do not understand ).
What should be my choices, if I want to stay within distro kernel.
Thanks a lot.



On Feb 19, 2008 5:53 PM, Kyle McMartin <kyle(a)mcmartin.ca&gt; wrote:

>   On Tue, Feb 19, 2008 at 01:41:15PM +0200, Eugene Goubine wrote:
>  > Hello , dear list users.
>  > >From my module I am trying to register for the system suspend using the
>  *
>  > register_pm_notifier(nb)*
>  > which is expanded to *blocking_notifier_chain_register(&pm_chain_head,
>  nb).*
>  > **
>  > I have a linker warning which tells "pm_chain_head" is undefined. I do
>  > see  pm_chain_head in my /proc/kallsyms.
>  > What do I miss? Thank you.
>
>  It's hard to comment on it if you don't attach the source code...
>
>  At a guess, you tried using register_pm_notifier, that failed to link,
>  so you tried to use the function that it calls, which won't work since
>  pm_chain_head is static to the kernel/power/main.c compilation unit.
>
>  License your module under the GPL and add MODULE_LICENSE("GPL") and
>  you'll be able to use the register_pm_notifier export...
>
>  regards, Kyle
>

[Kyle McMartin]

On Tue, Feb 19, 2008 at 06:43:16PM +0200, Eugene Goubine wrote:
>  Kyle, thanks for reffering,but it seems like GPL is not the case.
>  I want to write a module to track netdevices present.
>  Sort of a protocol sitting there. It is GPL'ed, but register_pm_notifier
>  usage ( as you can see in sources)
>  gives linker warning "pm_chain_head undefined",since register_pm_notifier is
>  "static inline" and expanded
>  to blocking_notifier_chain_unregister(&pm_chain_head, nb).
>  Why do you say pm_chain_head is static there ? Is it because it is not
>  exported by EXPORT_SYMBOL ? 
What kernel are you building against? Do you have CONFIG_PM_SLEEP=y?

cheers, Kyle


>  So what does it have to do with the license ( which is already GPL,
> but I
>  just do not understand ). 
nothing in particular, it's just a linking restriction that might have
bitten you if you didn't know while writing your own module. (that there
are two different kinds of export, i mean.)

[Eugene Goubine]

Yes, every grep on SLEEP in .config is =y .
The problem still persists. have no clue about possible direction.
( I have full source to compile eith  etc..)

On Feb 20, 2008 12:12 AM, Kyle McMartin <kyle(a)mcmartin.ca&gt; wrote:

>  On Tue, Feb 19, 2008 at 06:43:16PM +0200, Eugene Goubine wrote:
>  > Kyle, thanks for reffering,but it seems like GPL is not the case.
>  > I want to write a module to track netdevices present.
>  > Sort of a protocol sitting there. It is GPL'ed, but register_pm_notifier
>  > usage ( as you can see in sources)
>  > gives linker warning "pm_chain_head undefined",since
>  register_pm_notifier is
>  > "static inline" and expanded
>  > to blocking_notifier_chain_unregister(&pm_chain_head, nb).
>  > Why do you say pm_chain_head is static there ? Is it because it is not
>  > exported by EXPORT_SYMBOL ?
>
>  What kernel are you building against? Do you have CONFIG_PM_SLEEP=y?
>
>  cheers, Kyle
>
>
>  > So what does it have to do with the license ( which is already GPL, but
>  I
>  > just do not understand ).
>
>  nothing in particular, it's just a linking restriction that might have
>  bitten you if you didn't know while writing your own module. (that there
>  are two different kinds of export, i mean.)
>