linux-kernel - Re: RFD: Should we remove the HLT check? (was Re: [PATCH 1/8] x86: avoid check hlt if no timer interrupts)

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Message-ID: <4BE479EA.3080005@zytor.com>
Date:	Fri, 07 May 2010 13:36:58 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
CC:	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Alek Du <alek.du@...el.com>,
	Feng Tang <feng.tang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jacob Pan <jacob.jun.pan@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan.van.de.ven@...el.com>
Subject: Re: RFD: Should we remove the HLT check?  (was Re: [PATCH 1/8] x86:
 avoid check hlt if no timer interrupts)

On 05/07/2010 01:33 PM, Arjan van de Ven wrote:
> On 5/7/2010 13:32, H. Peter Anvin wrote:
>>
>> I really wish I knew the exact systems affected by the HLT bug.  If I
>> remember correctly, it was some 386 systems -- or possibly 486 systems
>> as well -- a very long time ago.  This test just provides a diagnosis if
>> the system really is bad (it hangs with an obvious message) at the cost
>> of some 40 ms to the system boot time.  I suspect C1 (HLT) being broken
>> is not anywhere close to the predominant power management problem in the
>> current day, and as such I'm wondering if this particular test hasn't
>> outlived its usefulness.
>>
>> Thoughts?
> 
> we could at least hide it behind the "don't run on pentium or newer" config options..

I'd be cool skipping it for family 5 or newer.  I'm just wondering if we
should kill it completely -- IIRC it was only a handful of 386/486
systems which had problems, usually due to marginal power supplies which
couldn't handle the noise of a variable load (DOS not having any power
management would run at a reliable 100% load) -- that's not exactly the
type of systems which would have survived to modern day.

	-hpa

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