linux-kernel - Re: [RFC PATCH 22/23] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter

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Date:   Tue, 12 Jun 2018 22:26:57 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Andi Kleen <andi.kleen@...el.com>, Ashok Raj <ashok.raj@...el.com>,
        Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        sparclinux@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Jacob Pan <jacob.jun.pan@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Don Zickus <dzickus@...hat.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Weisbecker <frederic@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Babu Moger <babu.moger@...cle.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Colin Ian King <colin.king@...onical.com>,
        Byungchul Park <byungchul.park@....com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Christoffer Dall <cdall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        iommu@...ts.linux-foundation.org
Subject: Re: [RFC PATCH 22/23] watchdog/hardlockup/hpet: Only enable the HPET
 watchdog via a boot parameter

On 06/12/2018 05:57 PM, Ricardo Neri wrote:
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f2040d4..a8833c7 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2577,7 +2577,7 @@
>  			Format: [state][,regs][,debounce][,die]
>  
>  	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
> -			Format: [panic,][nopanic,][num]
> +			Format: [panic,][nopanic,][num,][hpet]
>  			Valid num: 0 or 1
>  			0 - turn hardlockup detector in nmi_watchdog off
>  			1 - turn hardlockup detector in nmi_watchdog on

This says that I can use "nmi_watchdog=hpet" without using 0 or 1.
Is that correct?

> @@ -2587,6 +2587,9 @@
>  			please see 'nowatchdog'.
>  			This is useful when you use a panic=... timeout and
>  			need the box quickly up again.
> +			When hpet is specified, the NMI watchdog will be driven
> +			by an HPET timer, if available in the system. Otherwise,
> +			the perf-based implementation will be used.
>  
>  			These settings can be accessed at runtime via
>  			the nmi_watchdog and hardlockup_panic sysctls.


thanks,
-- 
~Randy