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: <4BE493D6.6000105@zytor.com>
Date:	Fri, 07 May 2010 15:27:34 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Arjan van de Ven <arjan@...ux.intel.com>,
	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 03:24 PM, Alan Cox wrote:
>> 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.
> 
> Also SMM and hardware bugs on some platforms - Cyrix MediaGX 5510 for
> example where a hlt at the wrong moment during ATA transfers hung the box
> until power cycle. But all old old stuff.

I think family < 5 seems a reasonable cutoff.

Note that the ATA transfer bug you describe above would not be caught by
the existing check.

	-hpa

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