linux-kernel - Re: [PATCH RFC] x86/mce: Move MCE sysfs attributes out of the per-cpu location

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Message-ID: <503DEE3C.6020406@linux.vnet.ibm.com>
Date:	Wed, 29 Aug 2012 15:56:04 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Borislav Petkov <bp@...64.org>
CC:	tony.luck@...el.com, andi@...stfloor.org, ananth@...ibm.com,
	x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
	hpa@...or.com, tglx@...utronix.de, linux-edac@...r.kernel.org
Subject: Re: [PATCH RFC] x86/mce: Move MCE sysfs attributes out of the per-cpu
 location

On 08/29/2012 03:43 PM, Borislav Petkov wrote:
> On Wed, Aug 29, 2012 at 01:11:55PM +0530, Naveen N. Rao wrote:
>> All the MCE attributes currently exported via sysfs appear under
>> /sys/devices/system/machinecheck/machinecheck<n>/. Pretty much all of these
>> are global in nature and not specific to a processor. We have around 7
>> attributes duplicated across each processor and on multi-core multi-socket
>> machines, this amounts to quite a large number. So, move these out under
>> /sys/devices/system/machinecheck/ where they rightly belong.
>>
>> Note: I'm not sure if it's ok to change sysfs entries and this does break
>> userspace tools that depend on the current path for some of these attributes.
>> So, they will need to be updated to use the new path. However, if we ever get
>> to a point where cpu0 can be offlined, these tools will need to be updated
>> anyway (as they mostly hardcode machinecheck0 currently)
>
> How do you know that for all tools out there?

I don't - I've seen mcelog and related tools and they look in machinecheck0.

>
> I know, I know, moving them to /sys/.../machinecheck/ is the right thing
> to do but they're exposed to userspace and we're breaking it with this
> patch. And we don't break userspace so I'd guess we're stuck with the
> current situation.

Hmmm.. Can't we just deprecate these? ;)
Perhaps we can consider adding newer tunables in the right place.


Thanks,
Naveen

>
> Sorry.
>

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