Linux 2.4 scheduler is RTOS-alike?

[Ming Lei]

this question is regarding linux kernel 2.4.7-2.4.20.
linux 2.4 kernel does support real time sheduler. If using FIFO real time
schedule policy, would the case that higher priority thread starve the lower
priority thread happen?  Similarly, let's say an example: if I have higher
prioority thread A and lower priority thread B, thread A is running without
any wait or blocking, is there a possiblity that 2.4 scheduler may want to
switch to thread B? Why?

If I want to instrument the 2.4 kernel to print out the message for every
thread context switch, where should I put the trace point?