[RFC PATCH 12/23] kernel/watchdog: Introduce a struct for NMI watchdog operations

[Peter Zijlstra]

On Wed, Jun 13, 2018 at 05:41:41PM +1000, Nicholas Piggin wrote:
> On Tue, 12 Jun 2018 17:57:32 -0700
> Ricardo Neri <ricardo.neri-calderon at linux.intel.com> wrote:
> 
> > Instead of exposing individual functions for the operations of the NMI
> > watchdog, define a common interface that can be used across multiple
> > implementations.
> > 
> > The struct nmi_watchdog_ops is defined for such operations. These initial
> > definitions include the enable, disable, start, stop, and cleanup
> > operations.
> > 
> > Only a single NMI watchdog can be used in the system. The operations of
> > this NMI watchdog are accessed via the new variable nmi_wd_ops. This
> > variable is set to point the operations of the first NMI watchdog that
> > initializes successfully. Even though at this moment, the only available
> > NMI watchdog is the perf-based hardlockup detector. More implementations
> > can be added in the future.
> 
> Cool, this looks pretty nice at a quick glance. sparc and powerpc at
> least have their own NMI watchdogs, it would be good to have those
> converted as well.

Yeah, agreed, this looks like half a patch.

> Is hpet a cross platform thing, or just x86? We should avoid
> proliferation of files under kernel/ I think, so with these watchdog
> driver structs then maybe implementations could go in drivers/ or
> arch/

HPET is mostly an x86 thing (altough it can be found elsewhere), but the
whole thing relies on the x86 NMI mechanism and is thus firmly arch/
material (like the sparc and ppc thing).