Re: [rtl] Weird side-effect with FIFOs

[Paolo Mantegazza <mantegazza@aero.polimi.it>]

Laurent.Kersten@alcatel.be wrote:
> 
> Hello,
> 
> I discovered something strange with the FIFOs (RTAI-1.5). I wrote a small RT task that basically put a character to a FIFO, do a few thing (print a message in the log file and do a few computation). and then read the FIFO again. This is the only RT task in
> the system. So normally, you expect every read to succeed. However, I observed a strangebehaviour. If when my task is running, I lauch a "cat </dev/rtf10" process on the shell prompt. The command gives me characters !!!!!!!!. So, this means that the
> rtf_put function stop the thread and do some rescheduling and so allow the linux process to read the character ... And the consequence is .... a simple Linux user space program is able to preempt a real time task which is not the expected behaviour in a
> realtime system.
> 
> Does anybody know a mean for solving this undesirable side effect ?
> 
> Laurent

Send me the code. I think I can easilly put a preemtion check in the
real time task and see if your assumption is right.

Ciao, Paolo.