Messages in this thread | | | Date | Fri, 20 Feb 2015 21:11:23 +0100 | From | Ingo Molnar <> | Subject | Re: smp_call_function_single lockups |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Fri, Feb 20, 2015 at 11:41 AM, Ingo Molnar <mingo@kernel.org> 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,
Ah, ok! Then the patch looks good to me.
( Originally we didn't wait for the ICR bit either, but then it was added due to later erratas and was eventually made an architectural requirement. )
> I agree that when doing other apic implementations, we > may need to guarantee atomicity for things like "wait for > apic idle, then send the ipi".
Yeah.
Thanks,
Ingo
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