Re: PMU and timer interrupts

[Stephane Eranian <eranian@hpl.hp.com>]

Ken,

On Mon, Feb 13, 2006 at 02:49:57PM -0800, Chen, Kenneth W wrote:
> Chen, Kenneth W wrote on Monday, February 13, 2006 12:32 PM
> > Stephane Eranian wrote on Monday, February 13, 2006 12:13 PM
> > > Jes seems to believe than this is more historical than anything for qla2xxx.
> > > Now what about the timer interrupt, why does it really need SA_INTERRUPT especially
> > > given that it is so high priority and with the TPR mechanism. IT seems to be
> > > a protection against MCA, IPI, IPI_RESCHEDULE based on the current layout.
> > 
> > scheduler_tick function expects irq off because it calls load_balance and
> > will muck around with runqueue list.  Won't that race with resched IPI if
> > irq is not masked?
> 
> NO! Ken needs more coffee Monday morning ....
> 
> I forgot that we don't check TIF_ flag when we are still on kernel stack.
> So resched IPI should be safe w.r.t timer interrupt because schedule is
> called after timer_interrupt finishes.
> 
Thanks for checking on this. That leaves us with regular IPI which is
can be quite vast and MCA.

-- 
-Stephane