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Date:   Wed, 27 Feb 2019 08:17:58 -0800
From:   "Paul E. McKenney" <paulmck@linux.ibm.com>
To:     Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@suse.de>,
        Ashok Raj <ashok.raj@intel.com>,
        Andi Kleen <andi.kleen@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Ricardo Neri <ricardo.neri@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Don Zickus <dzickus@redhat.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Frederic Weisbecker <frederic@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Babu Moger <babu.moger@oracle.com>,
        "David S. Miller" <davem@davemloft.net>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Colin Ian King <colin.king@canonical.com>,
        Byungchul Park <byungchul.park@lge.com>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Waiman Long <longman@redhat.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Christoffer Dall <cdall@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        David Rientjes <rientjes@google.com>,
        sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH v2 09/14] watchdog/hardlockup: Make
 arch_touch_nmi_watchdog() to hpet-based implementation
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 <1551283518-18922-10-git-send-email-ricardo.neri-calderon@linux.intel.com>
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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@zytor.com>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Andi Kleen <andi.kleen@intel.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Don Zickus <dzickus@redhat.com>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Frederic Weisbecker <frederic@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Babu Moger <babu.moger@oracle.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Philippe Ombredanne <pombredanne@nexb.com>
> Cc: Colin Ian King <colin.king@canonical.com>
> Cc: Byungchul Park <byungchul.park@lge.com>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: Christoffer Dall <cdall@linaro.org>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
> Cc: x86@kernel.org
> Cc: sparclinux@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@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.

							Thanx, Paul

>  extern void arch_touch_nmi_watchdog(void);
> +#else
> +# if !defined(CONFIG_HAVE_NMI_WATCHDOG)
> +static inline void arch_touch_nmi_watchdog(void) {}
> +# endif
> +#endif
> +
> +#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
>  extern void hardlockup_detector_perf_stop(void);
>  extern void hardlockup_detector_perf_restart(void);
>  extern void hardlockup_detector_perf_disable(void);
> -- 
> 2.17.1
>