linux-kernel - Re: [PATCH] x86, MCE: Kill CPU_POST

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Date:	Mon, 26 May 2014 22:01:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"ego@...ux.vnet.ibm.com" <ego@...ux.vnet.ibm.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] x86, MCE: Kill CPU_POST_DEAD

On Thu, May 22, 2014 at 09:55:38PM +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@...e.de>
> Date: Thu, 22 May 2014 16:40:54 +0200
> Subject: [PATCH] x86, MCE: Kill CPU_POST_DEAD
> 
> In conjunction with cleaning up CPU hotplug, we want to get rid of
> CPU_POST_DEAD. Kill this instance here and rediscover CMCI banks at the
> end of CPU_DEAD.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 68317c80de7f..bfde4871848f 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -2391,6 +2391,10 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
>  			threshold_cpu_callback(action, cpu);
>  		mce_device_remove(cpu);
>  		mce_intel_hcpu_update(cpu);
> +
> +		/* intentionally ignoring frozen here */
> +		if (!(action & CPU_TASKS_FROZEN))
> +			cmci_rediscover();
>  		break;
>  	case CPU_DOWN_PREPARE:
>  		smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
> @@ -2402,11 +2406,6 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
>  		break;
>  	}
>  
> -	if (action == CPU_POST_DEAD) {
> -		/* intentionally ignoring frozen here */
> -		cmci_rediscover();
> -	}
> -
>  	return NOTIFY_OK;
>  }

Ok, so I did a little hammering on this one by running a hotplug toggler
script, reading out files under /sys/devices/system/machinecheck... and
suspending to disk and resuming, all at the same time. 'Round 10ish
cycles I did and the box was chugging away happily without any issues.

So, I'm going to queue this one for 3.17, along with the
panic-on-timeout for the default tolerance level one:

http://lkml.kernel.org/r/20140523091041.GA21332@pd.tnic

if you don't have any objections. I'm saying 3.17 because both are
not really critical stuff and could use a full cycle of simmering in
linux-next just fine.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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