Semaphores on Linux target

Engineering 🇬🇧
francois
2012-05-02
2012-09-18

  • francois - 2012-05-02

    Hi,

    I need a way to use sems on my V3.4.2.0 arm-linux target.
    Using SysSemProcess lib makes segmentation fault when attempting to start the runtime, I think the lib might not be implemented on Linux in my current runtime version.

    Using SysSem, SysSemEnter or SysSemTry always return ERR_OK, no matter if the sem is locked or not!

    IF pSemHandle^ = RTS_INVALID_HANDLE THEN
   pSemHandle^ := SysSemCreate(ADR(semCreateResult));
END_IF
semTryResult:=SysSemTry(pSemHandle^);
semEnterResult:=SysSemEnter(pSemHandle^);

    pSemHandle is a pointer to a udint declared in a GVL.
    Obviously I have more code that later releases the sem when not needed anymore, but my problem is that I cannot check if the resource is free or not!

    I dont what to use SW FB for that because I want to make sure that the P and V functions will be "atomic".

    Anyone had any luck with this lib on an arm-linux target?

    Thanks!

     

  • kberlin - 2012-05-03

    There is an old bug report CDS-7499 that just says "Linux: Semaphores are not working correctly". But I think it would be best if you contacted 3S support directly.

    Best regards,
    Kristian Berlin

     

  • Jay - 2012-05-07

    Which Linux distro are you using? I noticed that Codesys (V. 3.4.x.x) Semaphores work if your Linux supports POSIX IPC Semaphores, but not with System V semaphores. Your Linux distro should support POSIX if you can find /dev/shm directory.

     

  • francois - 2012-05-09

    Interesting point, I am running linux-davinci, which support POSIX sems.
    I compiled a small c application that uses semaphores.h and sem_init, wait, post, destroy to test on the target and it runs smoothly, so I gess I'll have to upgrade my runtime to make it works.

    Anyway, thanks for your help!

     

  • sarathbabu - 2012-09-17

    Hi 

      I would like to know whether codesys can be used for programming embedded controllers and can I know one example how it is done for this linux and one embedded application

    Thanks

     

  • TimvH

    TimvH - 2012-09-17

    To use CoDeSys on your own embedded controller, you will need the CoDeSys Runtime Toolkit.
    Together with 3S-Smart Software Solutions you can then implement and adapt the runtime to your hardware.
    Please contact the sales team of 3S-Smart Software Solutions for further information.

     

  • sarathbabu - 2012-09-18

    Thanks for the info.Can I you give me a link for any existing embedded controller using codesys.It will be helpful for me.

     

  • TimvH

    TimvH - 2012-09-18

    I don't understand exactly what you mean:
    - If you want to buy an existing controller which can be programmed with CoDeSys you can go to the CoDeSys Device Directory and search http://www.3s-software.com/index.shtml? ... _directory
    - If you want to build your own controller you could choose any platform. See http://www.3s-software.com/index.shtml?en_CoDeSysSP_OEM (click on Linux) to see the details and requirements.
    I cannot advise you which platform is best.

     

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