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Date: Mon, 21 Nov 2016 12:48:58 -0500
From: Don Zickus <dzickus@redhat.com>
To: Prarit Bhargava <prarit@redhat.com>
Cc: linux-kernel@vger.kernel.org, Borislav Petkov <bp@suse.de>,
        Tejun Heo <tj@kernel.org>,
        Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
        Thomas Gleixner <tglx@linutronix.de>, Andi Kleen <ak@linux.intel.com>,
        Joshua Hunt <johunt@akamai.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] kernel/watchdog.c: Only output hw-PMU message once
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On Mon, Nov 21, 2016 at 11:35:19AM -0500, Prarit Bhargava wrote:
> When CONFIG_BOOTPARAM_HOTPLUG_CPU0 is enabled, the socket containing the
> boot cpu can be replaced.  During the hot add event, the message
> 
> NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
> 
> is output implying that the NMI was disabled at some point.  This is not the
> case and the message has caused confusion for users of systems that support
> socket removal.
> 
> This patch modifies the message so that it only outputs a single time
> during runtime.

Hmm, it occurred to me, with pr_info_once, what happens if you disable and
re-enable, is this still printed?

echo 0 > /proc/sys/kernel/watchdog
echo 1 > /proc/sys/kernel/watchdog

Cheers,
Don

> 
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Don Zickus <dzickus@redhat.com>
> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Joshua Hunt <johunt@akamai.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> ---
>  kernel/watchdog.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 9acb29f280ec..560414692c01 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -615,7 +615,7 @@ static int watchdog_nmi_enable(unsigned int cpu)
>  	if (!IS_ERR(event)) {
>  		/* only print for cpu0 or different than cpu0 */
>  		if (cpu == 0 || cpu0_err)
> -			pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
> +			pr_info_once("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
>  		goto out_save;
>  	}
>  
> -- 
> 1.7.9.3
>