Weird side-effect with FIFOs

[Laurent.Kersten@alcatel.be]

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