linux-kernel - Re: [RFC PATCH v2 13/14] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter

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Message-ID: <alpine.DEB.2.21.1903262223330.1789@nanos.tec.linutronix.de>
Date:   Tue, 26 Mar 2019 22:29:52 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Ashok Raj <ashok.raj@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Clemens Ladisch <clemens@...isch.de>,
        Arnd Bergmann <arnd@...db.de>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Nayna Jain <nayna@...ux.ibm.com>
Subject: Re: [RFC PATCH v2 13/14] watchdog/hardlockup/hpet: Only enable the
 HPET watchdog via a boot parameter

On Wed, 27 Feb 2019, Ricardo Neri wrote:
> +			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. Specifying
> +			hpet implies that nmi_watchdog is on.

How so?

> +static int __init hardlockup_detector_hpet_setup(char *str)
> +{
> +	if (strstr(str, "hpet"))
> +		hardlockup_use_hpet = true;

strstr()? Not really.

> +
> +	return 0;
> +}
> +__setup("nmi_watchdog=", hardlockup_detector_hpet_setup);
> +
>  /**
>   * hardlockup_detector_hpet_init() - Initialize the hardlockup detector
>   *
> @@ -405,6 +422,9 @@ int __init hardlockup_detector_hpet_init(void)
>  {
>  	int ret;
>  
> +	if (!hardlockup_use_hpet)
> +		return -ENODEV;

This should have been there in the patch which introduces
hardlockup_detector_hpet_init(). And this patch merily adds the command
line magic which sets that flag.

> +
>  	if (!is_hpet_enabled())
>  		return -ENODEV;
>  
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 367aa81294ef..28cad7310378 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -78,7 +78,7 @@ static int __init hardlockup_panic_setup(char *str)
>  		nmi_watchdog_user_enabled = 0;
>  	else if (!strncmp(str, "1", 1))
>  		nmi_watchdog_user_enabled = 1;
> -	return 1;
> +	return 0;

Why?

Thanks,

	tglx