Re: [PATCH 2/2] powernv/kdump: Fix cases where the kdump kernel can get HMI's

[Balbir Singh <bsingharora@gmail.com>]

On Fri, Dec 15, 2017 at 12:32 AM, Nicholas Piggin <npiggin@gmail.com> wrote:
> On Thu, 14 Dec 2017 23:16:26 +1100
> Balbir Singh <bsingharora@gmail.com> wrote:
>
>> On Thu, Dec 14, 2017 at 12:51 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
>
>
>> >> I can't call smp_send_nmi_ipi due to the nmi_ipi_busy_count and
>> >> I'm worried about calling a stale nmi_ipi_function via the
>> >> system_reset_exception path, if we are OK with it, I can revisit
>> >> the code path
>> >
>> > You shouldn't get a stale one, that would also be a bug -- we
>> > have to cope with NMIs coming in at any time that are triggered
>> > externally (not by smp_send_nmi_ipi), so if you see any bugs
>> > there those need to be fixed separately.
>> >
>>
>> Yes, I think it's a bug, nothing clears nmi_ipi_function (from what
>> I can see), so when the next NMI comes in and goes into
>> pnv_system_reset_exception
>> it'll execute the stale handler.
>
> The CPU won't be in the nmi_ipi_pending_mask though, so it shouldn't
> get that far. You could add a bit of paranoia to clear the function
> pointer I suppose, but AFAIKS it's not needed.
>

Yep your right, but these things are so subtle :) I will as paranoia
cleanup nmi_ipi_function, but I'll add that as a TODO

Balbir Singh.