Re: [PATCH v9 0/7] arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it

[Mark Rutland]

On Mon, Aug 07, 2023 at 06:16:24PM +0530, Sumit Garg wrote:
> On Mon, 7 Aug 2023 at 16:11, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> > On Mon, Jul 24, 2023 at 08:55:44AM -0700, Doug Anderson wrote:
> > > On Thu, Jun 1, 2023 at 2:37 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
> > I'd also strongly prefer if we
> > could have separate IPI_CPU_BACKTRACE and IPI_CPU_KGDB IPIs,
> 
> With current logic of single debug IPI, it is not required for a user
> to enable KGDB in order to use that IPI for backtrace. The original
> motivation for this logic was that the IPIs are a scarce resource on
> arm64 as per comments from Marc. So I am fine either way to keep them
> separate or unified.
> 
> > and I think we can
> > do that either by unifying IPI_CPU_STOP && IPI_CPU_CRASH_STOP or by reclaiming
> > IPI_WAKEUP by reusing a different IPI for the parking protocol (e.g.
> > IPI_RESCHEDULE).
> 
> That sounds like a good cleanup.

I took a quick stab at removing IPI_WAKEUP, and it seems simple enough; patch
below.

Mark.

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