linux-kernel - Re: [RFC PATCH 0/6] jump label v3

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Message-ID: <4B047A81.3060104@zytor.com>
Date:	Wed, 18 Nov 2009 14:51:45 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jason Baron <jbaron@...hat.com>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	mathieu.desnoyers@...ymtl.ca, tglx@...utronix.de,
	rostedt@...dmis.org, andi@...stfloor.org, roland@...hat.com,
	rth@...hat.com, mhiramat@...hat.com
Subject: Re: [RFC PATCH 0/6] jump label v3

On 11/18/2009 02:43 PM, Jason Baron wrote:
> 
> I'm using an atomic 5 byte no-op for x86_64 and a long jump for 32-bit x86.
> My understanding is that not all 32-bit processors have an atomic 5 byte no-op,
> and thus using a long jump or jump 0, for the off case is the safest.
> 

67 66 8D 74 00 (lea si,[si+0]) should work as a 32-bit atomic NOP.  It's
not necessarily the fastest, though (I have no data on that.)
Similarly, 66 66 66 66 90 should also work.

	-hpa
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