Synchronous Message Passing

Shravan Rayanchu rshravankumar at
Fri Oct 8 17:58:30 CEST 2004

Actually the problem is something like this:

we are actually developing a MAC layer. So the
constraint is that user will use Kernel space (via sys
calls) and call functions like "connect". Sys call
then, forms the CONNECT-REQUEST and has to give it to
an RT Task.(In local m/c). 

// I need to have some mechanism of passing this
request (basically few bytes of data.)

RT Task will handle the request. The Syscall then HAS
to wait till it gets a CONNECT-CONFIRM from the RT
Task (REQUEST and CONFIRM are both structures) and
then do some processing and the return to the user
(the outcome of connect request.)

In my case, the RT Task, typically will have other
tasks to do, it wont call a rt_receive function and
wait!. That is, 'connect' is an ASYNCHRONOUS request
(the request can come at anytime) & RT Task wont be
waiting for it (RT Task wont block). 

// Any how rt_receive expects a RT Task to wait for,
while we are in a sys call (kernel space) - not an RT

RT Task will poll the FIFO or something occasionally
to check if there is a data and do some processing &
then returns CONFIRM structure. I called it
Synchronous message passing, cuz the sys call has to
WAIT till it gets a CONFIRM.

Please do help!

Thanks & regards,


> I do not understand the problem if you are writing a
> system call it 
> means that it has to be used by tasks anyhow.
> Moreove you have an RTAI 
> task in kernel space also. So whay not use RTAI rpc
> as it is, with the 
> adavantage of having it in distributed mode also
> It is not needed to be in real time to use RTAI in
> user space.
> Once more your solution has the name: LXRT (IMHO).
> Paolo.


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