linux-kernel - Re: [PATCH RFC] x86: fix confusing name of /proc/cpuinfo "ht" flag

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Message-ID: <4AFC274C.2020209@zytor.com>
Date:	Thu, 12 Nov 2009 07:18:36 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Dave Jones <davej@...emonkey.org.uk>
Subject: Re: [PATCH RFC] x86: fix confusing name of /proc/cpuinfo "ht" flag

On 11/12/2009 12:13 AM, Ingo Molnar wrote:
>>
>> /proc/cpuinfo is a user-space visible ABI.  Changing it is bad 
>> chicken.
> 
> Almost ... something is only an ABI if an actual application relies on 
> the 'ht' flag being there on non-hyperthreading CPUs. We dont know 
> whether there's any, but the likelyhood looks pretty low. Could park it 
> a branch for some time to see whether anything trips up.
> 

No, please.  We have had people who have "helpfully" tried to change
/proc/cpuinfo in the past, and what we find is that application
developers don't tell us -- they grumble among themselves and put out a
new release saying "fixes breakage introduced by Linux ..."

It's an ABI.  Keep it stable, please.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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