Re: Fw: [RFC] Strange code in cpu_idle()

["Paul E. McKenney" <paulmck@us.ibm.com>]

On Mon, Dec 06, 2004 at 09:47:04AM -0700, Zwane Mwaikambo wrote:
> On Mon, 6 Dec 2004, Paul E. McKenney wrote:
> 
> > I am not going to claim to thoroughly understand the power-management
> > code, but do have an additional question.
> > 
> > What happens if the processor became aware of a new grace period just
> > before entering pm_idle?  I could imagine this code simply refusing
> > to power down the processor if there was a pending grace period, but
> > I don't see any sign of this.  I could also imagine somehow deferring
> > interrupts until pm_idle exits.  I don't see anything that looks like
> > it does this, but don't claim to be any sort of power-management
> > expert.
> 
> Are you referring to the synchronize_kernel side? That's basically unload 
> module path so it's ok if it sits there for a bit, but it should only last 
> for as long as the next interrupt, which would be a pretty short perid 
> considering HZ=1000. But the usage still has a race and hence invalid as 
> pointed out by Dipankar

My bad -- I hadn't read through the entire thread before responding,
so was speculating on how it might manage to be correct.

							Thanx, Paul