From: raimue@codingfarm.de (Rainer Müller)
To: kernelnewbies@lists.kernelnewbies.org
Subject: cpu_relax(), rep: nop, and PAUSE
Date: Wed, 20 Feb 2013 22:18:16 +0100 [thread overview]
Message-ID: <kg3eik$ank$1@ger.gmane.org> (raw)
In-Reply-To: <CAJJAcocc9FbgAUjRED_0iLt=iz58CrZf=hmSKZf91XANz+cgJw@mail.gmail.com>
On 2013-02-19 13:20, David Shwatrz wrote:
> We have:
> #define cpu_relax() asm volatile("rep; nop")
> in arch/x86/boot/boot.h.
>
> Why don't we use the PAUSE assembler instruction here ?
If you dig further into the Intel x86 manual, the machine instructions
'pause' and 'rep;nop' actually use the exact same encoding. As some
older assembler might not know the 'pause' mnemonic, using 'rep;nop'
here is most probably for backwards compatibility.
Rainer
prev parent reply other threads:[~2013-02-20 21:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-19 12:20 cpu_relax(), rep: nop, and PAUSE David Shwatrz
2013-02-19 18:58 ` Mulyadi Santosa
2013-02-19 21:41 ` Valdis.Kletnieks at vt.edu
2013-02-20 3:35 ` Adam Lee
2013-02-20 21:18 ` Rainer Müller [this message]
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