linux-kernel - Re: [PATCH] x86, mce: Don't initialize MCEs on unknown CPUs

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Message-ID: <4A89409B.8020103@linux.intel.com>
Date:	Mon, 17 Aug 2009 13:35:55 +0200
From:	Andi Kleen <ak@...ux.intel.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	tglx@...utronix.de, Yinghai Lu <yinghai@...nel.org>,
	Huang Ying <ying.huang@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [PATCH] x86, mce: Don't initialize MCEs on unknown CPUs

Ingo Molnar wrote:

> 
> btw., i found the bug - it's due to:
> 
>   # CONFIG_CPU_SUP_INTEL is not set

Ah, thanks for debugging. Very tricky and nasty. Perhaps these options are more trouble
than what they save in code.

>  static void __cpuinit mce_ancient_init(struct cpuinfo_x86 *c)
> @@ -1342,11 +1352,10 @@ void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
>  	if (!mce_available(c))
>  		return;
>  
> -	if (mce_cap_init() < 0) {
> +	if (mce_cap_init() < 0 || mce_cpu_quirks(c) < 0) {
>  		mce_disabled = 1;
>  		return;
>  	}
> -	mce_cpu_quirks(c);

I'm very pedantic here and it's more a theoretical problem, but mce_cap_init() allocates
memory which you leak and this could rerun on each CPU hotplug. So if you have a unknown CPU and do
a lot of CPU hotadds in a loop then you would eventually fill all memory.
Better kfree() the bank arrays.

-Andi
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