linux-kernel - Re: [RFC PATCH v2 11/14] x86/watchdog/hardlockup: Add an HPET-based hardlockup detector

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Message-ID: <20190409110340.GS4038@hirez.programming.kicks-ass.net>
Date:   Tue, 9 Apr 2019 13:03:40 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Ashok Raj <ashok.raj@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        "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 11/14] x86/watchdog/hardlockup: Add an HPET-based
 hardlockup detector

On Wed, Feb 27, 2019 at 08:05:15AM -0800, Ricardo Neri wrote:
> diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h
> index 4d559e0c746f..15dc3b576496 100644
> --- a/arch/x86/include/asm/hpet.h
> +++ b/arch/x86/include/asm/hpet.h
> @@ -123,12 +123,24 @@ struct hpet_hld_data {
>  	u32		num;
>  	u32		flags;
>  	u64		ticks_per_second;
> +	u32		handling_cpu;
> +	struct cpumask	cpu_monitored_mask;
> +	struct msi_msg	msi_msg;
>  };

Please don't use struct cpumask unless you absolutely have to.

The above is better written as:


	struct hpet_hld_data {
		...
		unsigned long cpumask[0];
	};

and allocated using:

	struct hpet_hld_data *hhd = kzalloc(sizeof(struct hpet_hld_data) + cpumask_size());

and used as:

	to_cpumask(hhd->cpumask);