linux-kernel - Re: Does Itanium permit speculative stores?

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Message-ID: <52957B5E.60701@jonmasters.org>
Date:	Tue, 26 Nov 2013 23:55:58 -0500
From:	Jon Masters <jonathan@...masters.org>
To:	paulmck@...ux.vnet.ibm.com
CC:	tony.luck@...el.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: Does Itanium permit speculative stores?

On 11/11/2013 12:13 PM, Paul E. McKenney wrote:
> Hello, Tony,
> 
> Does Itanium permit speculative stores?  For example, on Itanium what are
> the permitted outcomes of the following litmus test, where both x and y
> are initially zero?
> 
> 	CPU 0				CPU 1
> 
> 	r1 = ACCESS_ONCE(x);		r2 = ACCESS_ONCE(y);
> 	if (r1)				if (r2)
> 		ACCESS_ONCE(y) = 1;		ACCESS_ONCE(x) = 1;
> 
> In particular, is the outcome (r1 == 1 && r2 == 1) possible on Itanium
> given this litmus test?
> 
> 							Thanx, Paul
> 
> --
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> 

Btw, I was reading through some UEFI docs and noticed a reference to "A
Formal Specification of Intel Itanium Processor Family Memory Ordering",
then remembered this thread. In case it's of use:

http://www.intel.com/design/itanium/downloads/251429.htm

Jon.

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