linux-kernel - Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

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Message-ID: <20090522204246.GH846@one.firstfloor.org>
Date:	Fri, 22 May 2009 22:42:46 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Michael S. Zick" <lkml@...ethan.org>
Cc:	Samuel Thibault <samuel.thibault@...-lyon.org>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

> If it: "Does not make a difference" then it "Should not make a difference"
> but it does, try it yourself.  Its safe (if LOCK_PREFIX is in the proper
> places) - the machine will ignore the opcode if is recent enough to not
> need it - just trust the cpu's micro-code.

It doesn't ignore it, in fact it's extremly slow on some older systems
where all atomic operations are very costly.
That is why LOCK is avoided as much as possible.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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