Unable to remove kernel module showing permanent using lsmod

Unable to remove kernel module showing permanent using lsmod

[sakthi selvam]

Dear All,

Need your assistance:

Currently I am using Wind River Linux distribution OS with kernel
version 2.6.27.39 and Wind River version pne-3. After loading of my
kernel module, I found it was permanent in the kernel using lsmod (for
ex see below Ref 1). When I tried to remove, it was displaying as
?ERROR: Removing 'hsl_module': Device or resource busy?. For your
information, the same module is working fine with the Wind River pne-2
Linux Distribution OS with kernel version 2.6.21.
>From the kernel source, I came to know that only possibility of
showing permanent is ?if there is non-availability of cleanup_module
and with the availability of init_module?.

But in my case, cleanup module also available in memory, after loading
the module. I used to check using the file in /proc/kallsyms for the
availability of cleanup module in memory.

Thanks for reading. Prompt reply is expected to identify the root cause.

Ref 1:
Module                  Size  Used by
hsl_module            530454  0 [permanent]




Thanks,
Sakthi Selvam

Unable to remove kernel module showing permanent using lsmod

[Mulyadi Santosa]

On Thu, Mar 24, 2011 at 12:08, sakthi selvam <sakthi.cdm@gmail.com> wrote:
> But in my case, cleanup module also available in memory, after loading
> the module. I used to check using the file in /proc/kallsyms for the
> availability of cleanup module in memory.

AFAIK, such thing could happen due to certain data structure(s) from
that module that are continously accessed or locked. So, to avoid race
condition ( and missing pointer), keeping the module in memory is the
right way to do.

But of course, AFAIK too, you can try rmmod -f. But the risk is all yours.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

Unable to remove kernel module showing permanent using lsmod

[Kacrut]

On 03/24/2011 01:38 PM, Mulyadi Santosa wrote:
> On Thu, Mar 24, 2011 at 12:08, sakthi selvam<sakthi.cdm@gmail.com>  wrote:
>> But in my case, cleanup module also available in memory, after loading
>> the module. I used to check using the file in /proc/kallsyms for the
>> availability of cleanup module in memory.
> AFAIK, such thing could happen due to certain data structure(s) from
> that module that are continously accessed or locked. So, to avoid race
> condition ( and missing pointer), keeping the module in memory is the
> right way to do.
>
> But of course, AFAIK too, you can try rmmod -f. But the risk is all yours.
>
I got same problem too. Doing rmmod -f doesnt solve it. Any other solution?

Unable to remove kernel module showing permanent using lsmod

[Greg KH]

On Thu, Mar 24, 2011 at 02:47:15PM +0700, Kacrut wrote:
> On 03/24/2011 01:38 PM, Mulyadi Santosa wrote:
> > On Thu, Mar 24, 2011 at 12:08, sakthi selvam<sakthi.cdm@gmail.com>  wrote:
> >> But in my case, cleanup module also available in memory, after loading
> >> the module. I used to check using the file in /proc/kallsyms for the
> >> availability of cleanup module in memory.
> > AFAIK, such thing could happen due to certain data structure(s) from
> > that module that are continously accessed or locked. So, to avoid race
> > condition ( and missing pointer), keeping the module in memory is the
> > right way to do.
> >
> > But of course, AFAIK too, you can try rmmod -f. But the risk is all yours.
> >
> I got same problem too. Doing rmmod -f doesnt solve it. Any other solution?

Nope, your kernel is probably configured to not allow kernel modules to
be unloaded.

I would ask your vendor about this as they are the ones that can support
your kernel the best, not the community.

best of luck,

greg k-h

Unable to remove kernel module showing permanent using lsmod

[Dave Hylands]

Hi sakthi,

On Wed, Mar 23, 2011 at 10:08 PM, sakthi selvam <sakthi.cdm@gmail.com> wrote:
> Dear All,
>
> Need your assistance:
>
> Currently I am using Wind River Linux distribution OS with kernel
> version 2.6.27.39 and Wind River version pne-3. After loading of my
> kernel module, I found it was permanent in the kernel using lsmod (for
> ex see below Ref 1). When I tried to remove, it was displaying as
> ?ERROR: Removing 'hsl_module': Device or resource busy?. For your
> information, the same module is working fine with the Wind River pne-2
> Linux Distribution OS with kernel version 2.6.21.
> >From the kernel source, I came to know that only possibility of
> showing permanent is ?if there is non-availability of cleanup_module
> and with the availability of init_module?.
>
> But in my case, cleanup module also available in memory, after loading
> the module. I used to check using the file in /proc/kallsyms for the
> availability of cleanup module in memory.
>
> Thanks for reading. Prompt reply is expected to identify the root cause.
>
> Ref 1:
> Module ? ? ? ? ? ? ? ? ?Size ?Used by
> hsl_module ? ? ? ? ? ?530454 ?0 [permanent]

Modules show up as permanent when they don't have a module_exit
procedure declared. Since no module_exit was provided, they can't be
unloaded.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

Unable to remove kernel module showing permanent using lsmod

[sakthi selvam]

Dear all,

                Thanks for your suggestion. Finally, I identified the
solution for the permanent issued I faced after loading my kernel module.
The solution is the kernel macro; 'USE_IMMEDIATE' has to be defined (to be
given as -DUSE_IMMEDIATE along with compiler flags) during compilation of my
module. Actually, I don't know much deep about the usage of this kernel
macro and how it resolves the issue, but one thing I came to know that it
was used during module relocation while inserting the module. If anyone help
me to get know much about it, then it will be fine. Also, for your
information, I have used my own Makefile for compilation of kernel loadable
modules. So, I have to add myself this macro to get rid of this permanent
issue. Another fine solution is, you can make use of kernel build Makefile
itself (if linux kernel version is above 2.4) to build your kernel loadable
modules. Because it itself include all default macros and flags needed for
compilation of your module. I have specified below the sample Makefile for
compiling kernel loadable modules with kernel build Makefile.

*Reference:*

obj-m += hello.o

all:

                make -C /lib/modules/$(shell uname -r)/build M=$(PWD)
modules

clean:

                make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean



Regards,

Sakthi



On Thu, Mar 24, 2011 at 10:38 AM, sakthi selvam <sakthi.cdm@gmail.com>wrote:

> Dear All,
>
> Need your assistance:
>
> Currently I am using Wind River Linux distribution OS with kernel
> version 2.6.27.39 and Wind River version pne-3. After loading of my
> kernel module, I found it was permanent in the kernel using lsmod (for
> ex see below Ref 1). When I tried to remove, it was displaying as
> ?ERROR: Removing 'hsl_module': Device or resource busy?. For your
> information, the same module is working fine with the Wind River pne-2
> Linux Distribution OS with kernel version 2.6.21.
> From the kernel source, I came to know that only possibility of
> showing permanent is ?if there is non-availability of cleanup_module
> and with the availability of init_module?.
>
> But in my case, cleanup module also available in memory, after loading
> the module. I used to check using the file in /proc/kallsyms for the
> availability of cleanup module in memory.
>
> Thanks for reading. Prompt reply is expected to identify the root cause.
>
> Ref 1:
> Module                  Size  Used by
> hsl_module            530454  0 [permanent]
>
>
>
>
> Thanks,
> Sakthi Selvam
>
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Unable to remove kernel module showing permanent using lsmod

[Mulyadi Santosa]

On Sun, Apr 17, 2011 at 13:19, sakthi selvam <sakthi.cdm@gmail.com> wrote:
> Dear all,
>
> ??????????????? Thanks for your suggestion. Finally, I identified the
> solution for the permanent issued I faced after loading my kernel module.
> The solution is the kernel macro; 'USE_IMMEDIATE' has to be defined (to be
> given as -DUSE_IMMEDIATE along with compiler flags) during compilation of my
> module.

Great! :)

Well, I think this is what this list for...to help someone able to
solve his/her own problem... and for sure, you learn something :)

Regarding the macro, I never read about that before...quite likely
that's an internal "define" block that enable a block of code (ala "if
define then....")..and it seems, that's somewhat critical...

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com