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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: saffroy@ri.silicomp.fr (Jean-Marc Saffroy)
Cc: linux-kernel@vger.kernel.org, linux-smp@vger.kernel.org
Subject: Re: [Q] Implementation of spin_lock on i386: why "rep;nop" ?
Date: Mon, 17 Sep 2001 18:27:44 +0100 (BST)	[thread overview]
Message-ID: <E15j2BM-0007WU-00@the-village.bc.nu> (raw)
In-Reply-To: <Pine.LNX.4.31.0109171725140.26090-100000@sisley.ri.silicomp.fr> from "Jean-Marc Saffroy" at Sep 17, 2001 06:16:48 PM

> The "rep;nop" line looks dubious, since the IA-32 programmer's manual from
> Intel (year 2001) mentions that the behaviour of REP is undefined when it
> is not used with string opcodes. BTW, according to the same manual, REP is
> supposed to modify ecx, but it looks like is is not the case here... which
> is fortunate, since ecx is never saved. :-)

rep nop is a pentium IV operation. Its retroactively after testing defined
to be portable and ok. 

Alan

  parent reply	other threads:[~2001-09-17 17:23 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-09-17 16:16 [Q] Implementation of spin_lock on i386: why "rep;nop" ? Jean-Marc Saffroy
2001-09-17 16:22 ` Dave Jones
2001-09-17 17:19   ` Jean-Marc Saffroy
2001-09-17 16:42 ` Richard B. Johnson
2001-09-17 17:06   ` Jonathan Lundell
2001-09-17 17:27 ` Alan Cox [this message]
2001-09-17 19:47   ` H. Peter Anvin
2001-09-19  3:42   ` Jamie Lokier
2001-09-19  4:06     ` Brian Gerst

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