[PlanetCCRMA] sched_setscheduler seeming to have no effect

Eric Weaver weav@sigma.net
Thu Dec 22 19:02:01 2005

I am running 2.4.24-1.ll.rh90.ccrma with ALSA 1.0.10 using snd-asihpi 
and usb audio over OSS (long story, that).  Since upgrading to ALSA 
1.0.10 from I think 1.0.4, I have been getting occasional overrun 
notifications from arecord (nothing drastic or too frightening but 
should not be happening at all with the buffer sizes I'm using).

My capture scripts are indeed running (sudoing as root) a little program 
I wrote to put arecord into SCHED_FIFO at priority 98 (using 
sched_setscheduler).  It reports normal completion of that system call, 
verified tracing it with gdb.

Yet when I test this using "sleep 999 &" and changing its scheduling as 
above, and look at the target process with "ps -O policy,rtprio" it 
reports "-" and "0", respectively.

Is there anything I'm missing here?


Eric Weaver
Palo Alto