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Date: Thu, 06 Jul 2006 14:28:15 -0600
From: "Chris Friesen" <cfriesen@nortel.com>
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To: Mark Lord <lkml@rtr.ca>
CC: Linus Torvalds <torvalds@osdl.org>, Arjan van de Ven <arjan@infradead.org>,
       "linux-os (Dick Johnson)" <linux-os@analogic.com>,
       Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch] spinlocks: remove 'volatile'
References: <20060705114630.GA3134@elte.hu> <20060705101059.66a762bf.akpm@osdl.org> <20060705193551.GA13070@elte.hu> <20060705131824.52fa20ec.akpm@osdl.org> <Pine.LNX.4.64.0607051332430.12404@g5.osdl.org> <20060705204727.GA16615@elte.hu> <Pine.LNX.4.64.0607051411460.12404@g5.osdl.org> <20060705214502.GA27597@elte.hu> <Pine.LNX.4.64.0607051458200.12404@g5.osdl.org> <Pine.LNX.4.64.0607051555140.12404@g5.osdl.org> <20060706081639.GA24179@elte.hu> <Pine.LNX.4.61.0607060756050.8312@chaos.analogic.com> <1152187268.3084.29.camel@laptopd505.fenrus.org> <44AD5357.4000100@rtr.ca> <Pine.LNX.4.64.0607061213560.3869@g5.osdl.org> <44AD658A.5070005@nortel.com> <44AD666B.1060500@rtr.ca>
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Mark Lord wrote:
> Chris Friesen wrote:
> 
>>
>> The "reordered" thing really only matters on SMP machines, no?
> 
> 
> Also (very much!) for device drivers.

Certainly...but I was coming at it from the perspective of userspace code.

As long as you're not talking to external devices, each cpu must be 
coherent with respect to itself, no?  It's allowed to execute 
out-of-order, but it needs to make sure that by doing so it doesn't 
cause changes that are visible to software.

Chris