On Fri, 2007-02-09 at 08:14 +1100, Benjamin Herrenschmidt wrote:

quoted

This patch adds a dummy affinity callback for the IPI "chip" to avoid
getting a warning ("Cannot set affinity for irq 251") when taking a
CPU offline via sysfs or during suspend.

Wouldn't be a better option to make sure they have IRQF_PERCPU set and
that we don't do the affinity thing on interrupts with that flag when 
offlining a CPU ?

Hmm. Yeah, something like that could be possible. Looking at
fixup_irqs() there is a test:

                if (irq_desc[irq].status & IRQ_PER_CPU)
                        continue;

but I'd have to dig what else this means.

johannes