[Xenomai-help] shm_open returns errno 38 - function not implemented

[Xenomai-help] shm_open returns errno 38 - function not implemented

[Yigal Goldberger]

Hi again,

I'm trying to create a shared memory area .
The system is a powerpc based board running linux kernel 2.6.29.4
and Xenomai 2.4.8 .
When I call shm_open from user space I get error 38 - function not implemented .

Thanks for the help,

Yigal Goldberger .



      

Re: [Xenomai-help] shm_open returns errno 38 - function not implemented

[Gilles Chanteperdrix]

Yigal Goldberger wrote:
> Hi again,
> 
> I'm trying to create a shared memory area .
> The system is a powerpc based board running linux kernel 2.6.29.4
> and Xenomai 2.4.8 .
> When I call shm_open from user space I get error 38 - function not implemented .

Normally, xenomai's shm_open tries to use the xenomai posix skin service
first, and if it fails (because the shared memory option was not enabled
in the posix skin configuration), falls back to linux service.

You get this error because:
- Xenomai posix skin's shared memory services are not enabled;
- your glibc does not support posix shared memory services (you can
check this in xenomai's config.log, there is a test detecting it).

Now, Xenomai posix skins's shared memory services are to be used if you
want to share memory between a kernel-space real-time posix application,
and a user-space real-time posix application.

So, if this is what you want to do, enable the xenomai posix skin shared
memory services in the kernel configuration (and please upgrade to
xenomai 2.4.9.1, because some bugs in the shared memory support were
fixed recently). If you want to share memory between two user-space
applications, you can also use xenomai shared memory services, but you
are probably better of upgrading your glibc to a glibc which support
posix shared memories.

-- 
                                          Gilles

Re: [Xenomai-help] shm_open returns errno 38 - function not implemented

[Yigal Goldberger]

Gilles,
Thanks for the answer.

I need shared memory only between user space applications , so I do prefer the second option. (our system is stable and we're satisfied from the performance , so we'd like to make as little changes as possible at this mature stage of the project ).
Can you advise me how to get the right version of the glibc (is it a stand alone change , simply replacing the glibc file , or do I need to make other changes ?)

Thanks again to the Xenomai operation , and to you personaly for your support !
Yigal Goldberger .


--- On Fri, 10/16/09, Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.orgg> wrote:

> From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
> Subject: Re: [Xenomai-help] shm_open returns errno 38 - function not implemented
> To: "Yigal Goldberger" <yigal_gold@domain.hid>
> Cc: xenomai@xenomai.org
> Date: Friday, October 16, 2009, 12:00 PM
> Yigal Goldberger wrote:
> > Hi again,
> > 
> > I'm trying to create a shared memory area .
> > The system is a powerpc based board running linux
> kernel 2.6.29.4
> > and Xenomai 2.4.8 .
> > When I call shm_open from user space I get error 38 -
> function not implemented .
> 
> Normally, xenomai's shm_open tries to use the xenomai posix
> skin service
> first, and if it fails (because the shared memory option
> was not enabled
> in the posix skin configuration), falls back to linux
> service.
> 
> You get this error because:
> - Xenomai posix skin's shared memory services are not
> enabled;
> - your glibc does not support posix shared memory services
> (you can
> check this in xenomai's config.log, there is a test
> detecting it).
> 
> Now, Xenomai posix skins's shared memory services are to be
> used if you
> want to share memory between a kernel-space real-time posix
> application,
> and a user-space real-time posix application.
> 
> So, if this is what you want to do, enable the xenomai
> posix skin shared
> memory services in the kernel configuration (and please
> upgrade to
> xenomai 2.4.9.1, because some bugs in the shared memory
> support were
> fixed recently). If you want to share memory between two
> user-space
> applications, you can also use xenomai shared memory
> services, but you
> are probably better of upgrading your glibc to a glibc
> which support
> posix shared memories.
> 
> -- 
>                
>                
>           Gilles
> 
> 

Re: [Xenomai-help] shm_open returns errno 38 - function not implemented

[Gilles Chanteperdrix]

Yigal Goldberger wrote:
> Gilles,
> Thanks for the answer.
> 
> I need shared memory only between user space applications , so I do prefer the second option. (our system is stable and we're satisfied from the performance , so we'd like to make as little changes as possible at this mature stage of the project ).
> Can you advise me how to get the right version of the glibc (is it a stand alone change , simply replacing the glibc file , or do I need to make other changes ?)
> 
> Thanks again to the Xenomai operation , and to you personaly for your support !
> Yigal Goldberger .

Any reasonably recent version of the glibc should do, but:
- you may be using the glibc from your toolchain, so changing glibc may
mean changing toolchain;
- well, the glibc is a bit the heart of the user-space support. It has
more than one files. And changing them may change a lot of things.

So, I think, the simpler thing for you is to use xenomai shared memories.


-- 
                                          Gilles

Re: [Xenomai-help] shm_open returns errno 38 - function not implemented

[Yigal Goldberger]

Hi Again Gilles,
I've also sent this mail to the DENX mailing list , since the toolchain is suplied by DENX.
Our board was ported some two months ago by DENX software based on the MPC8272 (freescale) .
I'd like to add the support for shared memory , but as I said I'd like to keep the system as untouched as possible - as I said It's been tested and is running stable and with good performance .
Since I know that these things are delicate, I'd appreciate your guidance as to which files I need replaced (by which files) , and which configurations need be changed .
Best Regards,
Yigal Goldberger .



--- On Fri, 10/16/09, Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.orgg> wrote:

> From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
> Subject: Re: [Xenomai-help] shm_open returns errno 38 - function not implemented
> To: "Yigal Goldberger" <yigal_gold@domain.hid>
> Cc: xenomai@xenomai.org
> Date: Friday, October 16, 2009, 4:18 PM
> Yigal Goldberger wrote:
> > Gilles,
> > Thanks for the answer.
> > 
> > I need shared memory only between user space
> applications , so I do prefer the second option. (our system
> is stable and we're satisfied from the performance , so we'd
> like to make as little changes as possible at this mature
> stage of the project ).
> > Can you advise me how to get the right version of the
> glibc (is it a stand alone change , simply replacing the
> glibc file , or do I need to make other changes ?)
> > 
> > Thanks again to the Xenomai operation , and to you
> personaly for your support !
> > Yigal Goldberger .
> 
> Any reasonably recent version of the glibc should do, but:
> - you may be using the glibc from your toolchain, so
> changing glibc may
> mean changing toolchain;
> - well, the glibc is a bit the heart of the user-space
> support. It has
> more than one files. And changing them may change a lot of
> things.
> 
> So, I think, the simpler thing for you is to use xenomai
> shared memories.
> 
> 
> -- 
>                
>                
>           Gilles
> 
>

Re: [Xenomai-help] shm_open returns errno 38 - function not implemented

[Gilles Chanteperdrix]

Yigal Goldberger wrote:
> Hi Again Gilles,
> I've also sent this mail to the DENX mailing list , since the toolchain is suplied by DENX.
> Our board was ported some two months ago by DENX software based on the MPC8272 (freescale) .
> I'd like to add the support for shared memory , but as I said I'd like to keep the system as untouched as possible - as I said It's been tested and is running stable and with good performance .
> Since I know that these things are delicate, I'd appreciate your guidance as to which files I need replaced (by which files) , and which configurations need be changed .
> Best Regards,
> Yigal Goldberger .

Could you show me the config.log file extracted from xenomai build
directory? After all, your glibc may support posix shared memories, but
something prevent them from working. In order for the posix shared
memories to work you must have:
- tmpfs support in the kernel configuration
- something like a script or a line in /etc/fstab which mounts a tmpfs
filesystem on /dev/shm (a drectory that must exist, too).

Otherwise, to enable shared memories in xenomai posix skin, you simply
have to enable the option in the kernel configuration, menu "Real-time
subsystem", Nucleus, Interfaces, POSIX API, then Option "shared memory".

-- 
					    Gilles.