[Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Michael Haberler]

Hi,

thanks to patience on this list we were able to build linuxcnc such that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a simulator/non-RT mode) and RTAI


I'm planning to adapt linuxcnc such that a universal binary can be built which runs under Xenomai, RT-PREEMPT and vanilla kernels as this will simplify logistics quite a bit; what I'd like have is reliable auto-detection of the kernel type and 'do the right thing' (RTAI will remain a separate build).

Autodetection could be one of several things - digging around with a shell script, using system calls, digging in /proc - unsure how to best do this, in particular I'm unsure how to tell an RT-PREEMPT kernel from a vanilla kernel 

I know it's a bit OT - still I'd be thankful for suggestions

any other low-lying cliffs I might hit?

- Michael

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Gilles Chanteperdrix]

On 01/14/2013 09:29 AM, Michael Haberler wrote:

> Hi,


Hi,

> 
> thanks to patience on this list we were able to build linuxcnc such
> that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a
> simulator/non-RT mode) and RTAI
> 
> 
> I'm planning to adapt linuxcnc such that a universal binary can be
> built which runs under Xenomai, RT-PREEMPT and vanilla kernels as
> this will simplify logistics quite a bit; what I'd like have is
> reliable auto-detection of the kernel type and 'do the right thing'
> (RTAI will remain a separate build).


I have no idea about preempt_rt, however, in order to detect xenomai,
you can check for /dev/rtheap. If it does not exist, xenomai programs
will not start anyway. Also, I guess for a universal binary, you would
dlopen xenomai libraries (native or posix, depending on the one you want
to use), if you want to do that, you have to pass --enable-dlopen-skins
to xenomai configure script.

Regards.

-- 
                                                                Gilles.

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Michael Haberler]

Gilles,

Am 14.01.2013 um 12:57 schrieb Gilles Chanteperdrix:

> On 01/14/2013 09:29 AM, Michael Haberler wrote:
> 
>> Hi,
> 
> 
> Hi,
> 
>> 
>> thanks to patience on this list we were able to build linuxcnc such
>> that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a
>> simulator/non-RT mode) and RTAI
>> 
>> 
>> I'm planning to adapt linuxcnc such that a universal binary can be
>> built which runs under Xenomai, RT-PREEMPT and vanilla kernels as
>> this will simplify logistics quite a bit; what I'd like have is
>> reliable auto-detection of the kernel type and 'do the right thing'
>> (RTAI will remain a separate build).
> 
> 
> I have no idea about preempt_rt, however, in order to detect xenomai,
> you can check for /dev/rtheap. If it does not exist, xenomai programs
> will not start anyway. Also, I guess for a universal binary, you would
> dlopen xenomai libraries (native or posix, depending on the one you want
> to use), if you want to do that, you have to pass --enable-dlopen-skins
> to xenomai configure script.

thanks, that is a good idea to verify the libraries are in place; I had to use --enable-dlopen-skins anyway to make Python imports happy.

I'll muddle my way through some string matching to find rt-preempt running; https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO#Checking_the_Kernel gives some hints

Is there any chance somebody runs Xenomai AND RT_PREEMPT patches applied? I heard a rumor but havent actually seen that

regards

- Michael

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Philippe Gerum]

On 01/14/2013 01:05 PM, Michael Haberler wrote:
> Gilles,
>
> Am 14.01.2013 um 12:57 schrieb Gilles Chanteperdrix:
>
>> On 01/14/2013 09:29 AM, Michael Haberler wrote:
>>
>>> Hi,
>>
>>
>> Hi,
>>
>>>
>>> thanks to patience on this list we were able to build linuxcnc such
>>> that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a
>>> simulator/non-RT mode) and RTAI
>>>
>>>
>>> I'm planning to adapt linuxcnc such that a universal binary can be
>>> built which runs under Xenomai, RT-PREEMPT and vanilla kernels as
>>> this will simplify logistics quite a bit; what I'd like have is
>>> reliable auto-detection of the kernel type and 'do the right thing'
>>> (RTAI will remain a separate build).
>>
>>
>> I have no idea about preempt_rt, however, in order to detect xenomai,
>> you can check for /dev/rtheap. If it does not exist, xenomai programs
>> will not start anyway. Also, I guess for a universal binary, you would
>> dlopen xenomai libraries (native or posix, depending on the one you want
>> to use), if you want to do that, you have to pass --enable-dlopen-skins
>> to xenomai configure script.
>
> thanks, that is a good idea to verify the libraries are in place; I had to use --enable-dlopen-skins anyway to make Python imports happy.
>
> I'll muddle my way through some string matching to find rt-preempt running; https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO#Checking_the_Kernel gives some hints
>
> Is there any chance somebody runs Xenomai AND RT_PREEMPT patches applied? I heard a rumor but havent actually seen that

Yes, this works. The current target is ppc 85xx, but I don't see any 
showstopper for running such combo on other archs, provided the I-pipe 
patch is adapted to a -rt kernel. This requires Xenomai 2.6.1+, stock.

-- 
Philippe.

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[John Morris]

On 01/14/2013 08:07 AM, Philippe Gerum wrote:
> On 01/14/2013 01:05 PM, Michael Haberler wrote:
>> Is there any chance somebody runs Xenomai AND RT_PREEMPT patches
>> applied? I heard a rumor but havent actually seen that
> 
> Yes, this works. The current target is ppc 85xx, but I don't see any
>  showstopper for running such combo on other archs, provided the
> I-pipe patch is adapted to a -rt kernel. This requires Xenomai
> 2.6.1+, stock.

Comparing the xenomai-2.6.2 x86/patches directory and
http://www.kernel.org/pub/linux/kernel/projects/rt, it appears there's a
common kernel version in 3.2.21.

I'm preparing RPM packages for 3.5 because I assume that's where most
development and bug fixing is going on, and because I hope the work will
be useful beyond the LinuxCNC community.  Unfortunately, RT_PREEMPT
seems to skip linux 3.5 entirely, jumping from 3.4 to 3.6.

	John

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Jan Kiszka]

On 2013-01-16 07:55, John Morris wrote:
> On 01/14/2013 08:07 AM, Philippe Gerum wrote:
>> On 01/14/2013 01:05 PM, Michael Haberler wrote:
>>> Is there any chance somebody runs Xenomai AND RT_PREEMPT patches
>>> applied? I heard a rumor but havent actually seen that
>>
>> Yes, this works. The current target is ppc 85xx, but I don't see any
>>  showstopper for running such combo on other archs, provided the
>> I-pipe patch is adapted to a -rt kernel. This requires Xenomai
>> 2.6.1+, stock.
> 
> Comparing the xenomai-2.6.2 x86/patches directory and
> http://www.kernel.org/pub/linux/kernel/projects/rt, it appears there's a
> common kernel version in 3.2.21.
> 
> I'm preparing RPM packages for 3.5 because I assume that's where most
> development and bug fixing is going on, and because I hope the work will
> be useful beyond the LinuxCNC community.  Unfortunately, RT_PREEMPT
> seems to skip linux 3.5 entirely, jumping from 3.4 to 3.6.

I-pipe also jumps, and now happened to land on 3.5 with its latest fixes
and features. When we jump the next time, we should probably pick 3.8 as
target for that reason. I may look into this soon. But I'm also
considering to backport recent work to 3.4 (for x86 targets at least).

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Gilles Chanteperdrix]

On 01/16/2013 09:13 AM, Jan Kiszka wrote:

> On 2013-01-16 07:55, John Morris wrote:
>> On 01/14/2013 08:07 AM, Philippe Gerum wrote:
>>> On 01/14/2013 01:05 PM, Michael Haberler wrote:
>>>> Is there any chance somebody runs Xenomai AND RT_PREEMPT patches
>>>> applied? I heard a rumor but havent actually seen that
>>>
>>> Yes, this works. The current target is ppc 85xx, but I don't see any
>>>  showstopper for running such combo on other archs, provided the
>>> I-pipe patch is adapted to a -rt kernel. This requires Xenomai
>>> 2.6.1+, stock.
>>
>> Comparing the xenomai-2.6.2 x86/patches directory and
>> http://www.kernel.org/pub/linux/kernel/projects/rt, it appears there's a
>> common kernel version in 3.2.21.
>>
>> I'm preparing RPM packages for 3.5 because I assume that's where most
>> development and bug fixing is going on, and because I hope the work will
>> be useful beyond the LinuxCNC community.  Unfortunately, RT_PREEMPT
>> seems to skip linux 3.5 entirely, jumping from 3.4 to 3.6.
> 
> I-pipe also jumps, and now happened to land on 3.5 with its latest fixes
> and features. When we jump the next time, we should probably pick 3.8 as
> target for that reason. I may look into this soon. But I'm also
> considering to backport recent work to 3.4 (for x86 targets at least).


I may jump to 3.6, at least for the ARM architecture. As for the
backports to 3.4, I still intend to re-release 2.6.2, so, it would be
nice to backport the bugfixes in the core-3.5 branch to the core-3.4 branch.

-- 
                                                                Gilles.

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Paul]

On Wednesday 16 January 2013, Gilles Chanteperdrix wrote:
> I may jump to 3.6, at least for the ARM architecture. As for the
> backports to 3.4, I still intend to re-release 2.6.2, so, it would be
> nice to backport the bugfixes in the core-3.5 branch to the core-3.4
> branch.

If you plan on updating the 3.2.21 ipipe-core patch, any chance you 
could include the fix to timer.c that you kindly provided a patch for 
(see 
http://www.xenomai.org/pipermail/xenomai/2012-August/026015.html )

I notice the bug affects all architectures, not just the ARM across the 
3.2.21 patch set. Other kernel versions already have the fix applied.
Thanks.


Regards, Paul.

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Jan Kiszka]

On 2013-01-14 09:29, Michael Haberler wrote:
> Hi,
> 
> thanks to patience on this list we were able to build linuxcnc such that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a simulator/non-RT mode) and RTAI
> 
> 
> I'm planning to adapt linuxcnc such that a universal binary can be built which runs under Xenomai, RT-PREEMPT and vanilla kernels as this will simplify logistics quite a bit; what I'd like have is reliable auto-detection of the kernel type and 'do the right thing' (RTAI will remain a separate build).
> 
> Autodetection could be one of several things - digging around with a shell script, using system calls, digging in /proc - unsure how to best do this, in particular I'm unsure how to tell an RT-PREEMPT kernel from a vanilla kernel 
> 
> I know it's a bit OT - still I'd be thankful for suggestions
> 
> any other low-lying cliffs I might hit?

I do not see why you application should have to tell -RT from vanilla
apart (syscalls are identical).

To handle the existence of Xenomai dynamically, you could push all
Xenomai API calls into a separate library, some abstraction layer (I
suppose you already have one in LinuxCNC), link that one against the
Xenomai libs, have a "vanilla" version as well that builds against
standard Linux, and then pull in the right version via dlopen (enable
support for this via --enable-dlopen-skins during Xenomai configure).
You could test in /proc for the existence of Xenomai before that, e.g.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux

Re: [Xenomai] universal application binary: how to auto-detect Xenomai/RT-PREEMPT/vanilla kernel

[Michael Haberler]

Am 14.01.2013 um 13:06 schrieb Jan Kiszka:

Jan,

> On 2013-01-14 09:29, Michael Haberler wrote:
>> Hi,
>> 
>> thanks to patience on this list we were able to build linuxcnc such that it runs on Xenomai, besides RT-PREEMPT, vanilla kernels (in a simulator/non-RT mode) and RTAI
>> 
>> 
>> I'm planning to adapt linuxcnc such that a universal binary can be built which runs under Xenomai, RT-PREEMPT and vanilla kernels as this will simplify logistics quite a bit; what I'd like have is reliable auto-detection of the kernel type and 'do the right thing' (RTAI will remain a separate build).
>> 
>> Autodetection could be one of several things - digging around with a shell script, using system calls, digging in /proc - unsure how to best do this, in particular I'm unsure how to tell an RT-PREEMPT kernel from a vanilla kernel 
>> 
>> I know it's a bit OT - still I'd be thankful for suggestions
>> 
>> any other low-lying cliffs I might hit?
> 
> I do not see why you application should have to tell -RT from vanilla
> apart (syscalls are identical).

you're right from the ABI point of view

when driving a machine some of the motion-related tasks are time critical and will fail with an error message if latency becomes too high; in the very minimum this has to be suppressed on a vanilla kernel after giving an initial warning, and proceed as a 'simulator configuration' (which really translates into 'no time guarantees whatsoever'); in that case one would also avoid loading actual hardware drivers to prevent damage


> To handle the existence of Xenomai dynamically, you could push all
> Xenomai API calls into a separate library, some abstraction layer (I
> suppose you already have one in LinuxCNC), link that one against the
> Xenomai libs, have a "vanilla" version as well that builds against
> standard Linux, and then pull in the right version via dlopen (enable
> support for this via --enable-dlopen-skins during Xenomai configure).
> You could test in /proc for the existence of Xenomai before that, e.g.

the current plan is to have the generic RTAPI abstraction layer in a .so plus shared objects as needed per flavor

- Michael


> 
> Jan
> 
> -- 
> Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
> Corporate Competence Center Embedded Linux