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Date:      Sun, 20 Jan 2002 19:08:08 -0500 (EST)
From:      Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
To:        louie@TransSys.COM
Cc:        arch@freebsd.org
Subject:   Re: 64 bit counters again 
Message-ID:  <200201210008.g0L088333530@khavrinen.lcs.mit.edu>
In-Reply-To: <mit.lcs.mail.freebsd-arch/200201202224.g0KMO8E56230@whizzo.transsys.com>
References:  <mit.lcs.mail.freebsd-arch/3C48A0E7.F97BC01@mindspring.com> <mit.lcs.mail.freebsd-arch/200201190350.g0J3oNN08944@khavrinen.lcs.mit.edu> <mit.lcs.mail.freebsd-arch/3C48FCEF.9190CA08@mindspring.com> <mit.lcs.mail.freebsd-arch/20020121082826.Z72285@gsmx07.alcatel.com.au>

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In article <mit.lcs.mail.freebsd-arch/200201202224.g0KMO8E56230@whizzo.transsys.com> you write:
>On an SMP system, some sort of locking is required to reliably
>update a 32 bit or 64 bit counter.  
[...]
>  - This can be a low-level architectural feature, such as the IA32
>LOCK prefix on an instruction to convert it into an atomic R-M-W
>operation.

Technically, atomic RMW is not considered locking.  (Hence, the class
of algorithms known as ``lock-free synchronization algorithms''.)

-GAWollman

-- 
Garrett A. Wollman   | O Siem / We are all family / O Siem / We're all the same
wollman@lcs.mit.edu  | O Siem / The fires of freedom 
Opinions not those of| Dance in the burning flame
MIT, LCS, CRS, or NSA|                     - Susan Aglukark and Chad Irschick

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