[etherlab-users] rtdm compile error

[Andreas Stewering-Bone]

Hello Ravi,

I will talk to Florian about the locking.

Maybe we will open a devel branch for the rtdm interface?


Best regards

Andreas


Am 06.05.2011 06:29, schrieb Ravi Chemudugunta:
> I was able to get the domain to exchange, I recompiled everything
> (including etherlabmaster-1.5, with the above hack of disabling
> callbacks).
>
>    
>> Which runtime enviroment do you use?
>>
>> Xenomai/RTAI?
>>      
> RTAI 3.8.1
>
>    
>> Kernelversion ?
>>      
> 2.6.29.5
>
>    
>> Distro?
>>      
> Custom distribution made using buildroot, and gcc 4.4.3.
>
> I think I have found the source of the deadlock. The rtdm module
> creates a mutex that it uses to marshal calls to etherlab kernel
> functions, however it also uses the same mutex reference in the
> callback functions it registers.
>
> module.c:599 (initalisation of rtdm module)
>    register locking / unlocking callback
> module.c:422 (marshal body)
>    >  marshal send call:
>    >  locks the mutex
>    >  calls ecrt_master_send
> master.c:2058 (send function body)
>    >  calls ec_master_inject_fsm_datagrams
> master.c:670 (inject function body)
>    >  calls the mutex callback (fsm_queue_locking_data)
>
> The callback registered @ initialisation time, attempts to lock the
> mutex, this is where the dead lock occurs.
>
> I think the intent of the callbacks has changed, it appears to be for
> the purposes of protecting the internal datagram queue; rather than
> for controlling when other threads (EoE) can also send/receive data.
> So I am not sure if they are needed to be used in this way as the user
> of the API does not have access to the internal queue directly anyway.
>
> Patch includes my effort so far, changed the nature of locking in
> inject datagrams to a speculative one.  Doing so solves the dead-lock,
> however, no domain data is exchanged, as inject datagrams never gets a
> chance, except through ecrt_master_send (where a lock has already been
> borrowed by rtdm callback).
>
> -ravi
>    


Mit freundlichem Gruß

Andreas Stewering-Bone

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