Re: smp_call_function_single lockups

From: Linus Torvalds
Date: Fri Feb 20 2015 - 15:03:10 EST

On Fri, Feb 20, 2015 at 11:41 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> I'm not so sure about that aspect: I think disabling IRQs
> might be necessary with some APICs (if lower levels don't
> disable IRQs), to make sure the 'local APIC busy' bit isn't
> set:

Right. But afaik not for the x2apic case, which this is. The x2apic
doesn't even have a busy bit, and sending the ipi is a single write,

I agree that when doing other apic implementations, we may need to
guarantee atomicity for things like "wait for apic idle, then send the

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at