[RFC PATCH v2 09/14] watchdog/hardlockup: Make arch_touch_nmi_watchdog() to hpet-based implementation

[Ricardo Neri]

On Wed, Feb 27, 2019 at 08:17:58AM -0800, Paul E. McKenney wrote:
> On Wed, Feb 27, 2019 at 08:05:13AM -0800, Ricardo Neri wrote:
> > CPU architectures that have an NMI watchdog use arch_touch_nmi_watchdog()
> > to briefly ignore the hardlockup detector. If the architecture does not
> > have an NMI watchdog, one can be constructed using a source of non-
> > maskable interrupts. In this case, arch_touch_nmi_watchdog() is common
> > to any underlying hardware resource used to drive the detector and needs
> > to be available to other kernel subsystems if hardware different from perf
> > drives the detector.
> > 
> > There exists perf-based and HPET-based implementations. Make it available
> > to the latter.
> > 
> > For clarity, wrap this function in a separate preprocessor conditional
> > from functions which are truly specific to the perf-based implementation.
> > 
> > Cc: "H. Peter Anvin" <hpa at zytor.com>
> > Cc: Ashok Raj <ashok.raj at intel.com>
> > Cc: Andi Kleen <andi.kleen at intel.com>
> > Cc: Tony Luck <tony.luck at intel.com>
> > Cc: "Rafael J. Wysocki" <rafael.j.wysocki at intel.com>
> > Cc: Don Zickus <dzickus at redhat.com>
> > Cc: Nicholas Piggin <npiggin at gmail.com>
> > Cc: Michael Ellerman <mpe at ellerman.id.au>
> > Cc: Frederic Weisbecker <frederic at kernel.org>
> > Cc: Alexei Starovoitov <ast at kernel.org>
> > Cc: Babu Moger <babu.moger at oracle.com>
> > Cc: "David S. Miller" <davem at davemloft.net>
> > Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> > Cc: Paul Mackerras <paulus at samba.org>
> > Cc: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> > Cc: Masami Hiramatsu <mhiramat at kernel.org>
> > Cc: Peter Zijlstra <peterz at infradead.org>
> > Cc: Andrew Morton <akpm at linux-foundation.org>
> > Cc: Philippe Ombredanne <pombredanne at nexb.com>
> > Cc: Colin Ian King <colin.king at canonical.com>
> > Cc: Byungchul Park <byungchul.park at lge.com>
> > Cc: "Paul E. McKenney" <paulmck at linux.vnet.ibm.com>
> > Cc: "Luis R. Rodriguez" <mcgrof at kernel.org>
> > Cc: Waiman Long <longman at redhat.com>
> > Cc: Josh Poimboeuf <jpoimboe at redhat.com>
> > Cc: Randy Dunlap <rdunlap at infradead.org>
> > Cc: Davidlohr Bueso <dave at stgolabs.net>
> > Cc: Christoffer Dall <cdall at linaro.org>
> > Cc: Marc Zyngier <marc.zyngier at arm.com>
> > Cc: Kai-Heng Feng <kai.heng.feng at canonical.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> > Cc: David Rientjes <rientjes at google.com>
> > Cc: "Ravi V. Shankar" <ravi.v.shankar at intel.com>
> > Cc: x86 at kernel.org
> > Cc: sparclinux at vger.kernel.org
> > Cc: linuxppc-dev at lists.ozlabs.org
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon at linux.intel.com>
> > ---
> >  include/linux/nmi.h | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/nmi.h b/include/linux/nmi.h
> > index 5a8b19749769..bf5ebcfdd590 100644
> > --- a/include/linux/nmi.h
> > +++ b/include/linux/nmi.h
> > @@ -94,8 +94,16 @@ static inline void hardlockup_detector_disable(void) {}
> >  # define NMI_WATCHDOG_SYSCTL_PERM	0444
> >  #endif
> > 
> > -#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
> > +#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF) || \
> > +    defined(CONFIG_X86_HARDLOCKUP_DETECTOR_HPET)
> 
> Why not instead make CONFIG_X86_HARDLOCKUP_DETECTOR_HPET select
> CONFIG_HARDLOCKUP_DETECTOR_PERF?  Keep the arch-specific details
> in the arch-specific files and all that.

Thanks for your feedback, Paul! The HPET implementation does not use
perf. Thus, in my opinion is not correct for the HPET HLD to select
the perf implementation. Patch 8 of this series splits the perf-specific
code and the generic hardlockup detector code. Does this make sense?

Thanks and BR,
Ricardo