[Xenomai] shared heap access mixing 32 and 64 bits applications

[Xenomai] shared heap access mixing 32 and 64 bits applications

[Stéphane Ancelot]

Hi,

Is it possible to access same shared memory heaps , between 32 and 64 
bits processes ?

Regards,

S.Ancelot

Re: [Xenomai] shared heap access mixing 32 and 64 bits applications

[Lassi Niemistö]

> Is it possible to access same shared memory heaps , between 32 and 64 bits processes ?

In regular linux I faced the wall when trying to protect the usage of the shared memory area by (pthread iirc) mutex/semaphore - those structures had differences between 32/64bit platforms. I don't know if situation is same in Xenomai but pay attention also to what you are going to put in the shared memory.

-Lassi

Re: [Xenomai] shared heap access mixing 32 and 64 bits applications

[Stéphane Ancelot]

Le 26/01/2017 à 11:12, Lassi Niemistö a écrit :
>> Is it possible to access same shared memory heaps , between 32 and 64 bits processes ?
> In regular linux I faced the wall when trying to protect the usage of the shared memory area by (pthread iirc) mutex/semaphore - those structures had differences between 32/64bit platforms. I don't know if situation is same in Xenomai but pay attention also to what you are going to put in the shared memory.
>
> -Lassi

I have now the answer regarding xenomai shared heaps between 32 and 64  
bits processes , here is the status, if you use the latest next xenomai 
branch.
within a system running 64 bits xenomai kernel, you can :
* use shared heap areas with 32 bits xenomai processes
* use shared heap areas with 64 bits xenomai processes
* you can not use shared heap areas between 32 and 64 bits xenomai 
processes.
Each area (32/64) are insulated, this incompatibility issue comes mainly 
from usage of size_t type in the xenomai  heap library which are 
different between 32 and 64 bits systems.
and maybe more other reasons ...

So, this is good to know that incompatibility , you can not mix both 
kind of processes in xenomai.



Regards,
S.Ancelot

Re: [Xenomai] shared heap access mixing 32 and 64 bits applications

[Philippe Gerum]

On 01/27/2017 08:54 AM, Stéphane Ancelot wrote:
> 
> 
> Le 26/01/2017 à 11:12, Lassi Niemistö a écrit :
>>> Is it possible to access same shared memory heaps , between 32 and 64
>>> bits processes ?
>> In regular linux I faced the wall when trying to protect the usage of
>> the shared memory area by (pthread iirc) mutex/semaphore - those
>> structures had differences between 32/64bit platforms. I don't know if
>> situation is same in Xenomai but pay attention also to what you are
>> going to put in the shared memory.
>>
>> -Lassi
> 
> I have now the answer regarding xenomai shared heaps between 32 and 64 
> bits processes , here is the status, if you use the latest next xenomai
> branch.
> within a system running 64 bits xenomai kernel, you can :
> * use shared heap areas with 32 bits xenomai processes
> * use shared heap areas with 64 bits xenomai processes
> * you can not use shared heap areas between 32 and 64 bits xenomai
> processes.
> Each area (32/64) are insulated, this incompatibility issue comes mainly
> from usage of size_t type in the xenomai  heap library which are
> different between 32 and 64 bits systems.
> and maybe more other reasons ...
> 
> So, this is good to know that incompatibility , you can not mix both
> kind of processes in xenomai.


There is absolutely no provision for sharing Xenomai sessions in general
between 32/64 bit applications, and there won't be any, ever. Mixed ABI
support relates to invoking 64bit kernel services from a 32bit
application, nothing beyond that.

-- 
Philippe.