preemption and scheduling of Pthreads

[don89]

Hi..

i think we can simulate preemption by using 2 different priority thread, am i true? I just try these scenario :
1. Create Thread A with priority 99 , SCHED_FIFO..
2. Create Thread B with priority 4 , SCHED_FIFO

Thread A started and doing some busy work.. I guess that Thread B wouldn't start until thread A finished, but I get thread B can run before Thread A finished (It just like a common task switching).. I'm sure my 2 thread has right priority.
and if thread B is doing some work and if i yield it to thread A, it should preempt it but this doesnt happen, do someone kno wats happening?

pls reply with your thought process
thanks

[bhatta_sobs]

Hi

I was trying to do something similar to this.
For me SCHED_FIFO is not working as I expect. I would expect the high priority thread to keep running until its job is done. But what I observe is that both the threads run round robin.

I had posted similar query on the forum:
"implementing-priority-based-preemtive-pthread.html"

Do you have any further leads in this ?

Thanks,
B