On Fri, 2009-03-06 at 11:24 +0100, Peter Zijlstra wrote: > On Fri, 2009-03-06 at 20:59 +1100, Benjamin Herrenschmidt wrote: > > > If you have distinct interrupt priorities, you can > > > > > > 1) provide an interrupt stack for each priority > > > 2) mask all lower priorities when handling one > > > > > > Would that not work? > > > > The PIC does that already. IE. it will only interrupt again before > > ->eoi() for an interrupt of a higher priority. But by using > > IRQF_DISABLED, you mask interrupts in the core, and thus effectively > > completely prevents the whole thing. > > > > > The problems with enabling irqs in hardirq handlers are that you get > > > unlimited irq nesting, which is bad for your stack, furthermore, somehow > > > people thing it makes things 'faster' because the irq-off latency goes > > > down. > > > > No, you don't get unlimited IRQ nesting, at least not on sane archs with > > a decent PIC that does things like what I described above :-) > > Right, welcome to x86 ;-) Ok, people put me straight here. Since linux not support interrupt priorities, wouldn't it simply be a matter of implementing local_irq_en/dis-able() as masking the lowest level you use to run normal interrupts on? That will leave your other interrupt level available as NMI/debug thingies. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
