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

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Date:	Mon, 17 Aug 2009 13:53:41 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...ux.intel.com>
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


* Andi Kleen <ak@...ux.intel.com> wrote:

> 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.

Not really, we dont re-run mce_cap_init() if MCE is disabled so 
there's no memory leak that would fill all memory.

	Ingo
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