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

[Nicholas Piggin <npiggin@gmail.com>]

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.

> I'll respin things based on the
> suggestion above
> and deal with any bugs as well.

Thanks,
Nick