linux-kernel - Re: Difference between atomic operations and memory barriers

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Message-ID: <4AE81625.5000500@panasas.com>
Date:	Wed, 28 Oct 2009 12:00:05 +0200
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Valdis.Kletnieks@...edu
CC:	"Leonidas ." <leonidas137@...il.com>,
	Chris Friesen <cfriesen@...tel.com>,
	Noah Watkins <noah@...hdesu.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Difference between atomic operations and memory barriers

On 10/27/2009 01:51 PM, Valdis.Kletnieks@...edu wrote:
> On Tue, 27 Oct 2009 00:30:45 +0530, "Leonidas ." said:
> 
>> So we can safely assume that pointer assignment will be done in an
>> atomic manner?
> 
> Has anybody ever actually made a *production* CPU that had non-atomic
> pointer assignments?  And how long before the crazed programmers lynched
> and burned the offending CPU designer at the stake? ;)
> 
> Non-atomic pointer assignments are the CPU design equivalent of Vogon poetry.
> Just Say No. With a shotgun if needed.

What don't you know? the CPU that started it all was like that, the x86 16-bit
"large" and "huge" model had a double register seg:offset set, also in-memory
was double-ints(2*16) even the i386 was running 16 bit modes for a long time.

Kernel still have 16-bit dosemu mode supported until today, no?

About the shotguns lynching and burning I'm not sure, but Intel survived
just fine.

Boaz
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