Re: RT question : softirq and minimal user RT priority

[Lee Revell <rlrevell@joe-job.com>]

Please don't trim CC lists

On Mon, 2006-04-17 at 09:21 -0400, Mark Hounschell wrote:
> Steven Rostedt wrote:
> >> Is the smallest usable real-time priority greater than the highest real-time softirq ?
> > 
> > Nope, you can use any rt priority you want.  It's up to you whether you
> > want to preempt the softirqs or not. Be careful, timers may be preempted
> > from delivering signals to high priority processes.  I have a patch to
> > fix this, but I'm waiting on input from either Thomas Gleixner or Ingo.
> > 
> > -- Steve
> 
> I know this is an old thread but I seem to be having a problem similar
> to this and I didn't find any real resolution in the archives.
> 
> I'm using the rt16 patch on 2.6.16.5 with complete preemption. I have a
> high priority rt compute bound task that isn't getting signals from a
> pci cards interrupt handler. Only when I insure the rt priority of the
> task is lower than the rt priority of the irq thread ([IRQ 193]) will my
> task receive signals.
> 
> Is this a bug? Is the bug in my interrupt handler? Or is this expected
> and acceptable?

It's expected if your high priority RT task never gives up the CPU - if
this is the case the IRQ thread should have higher priority.

Lee