lkml.org 
[lkml]   [2001]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Q] Implementation of spin_lock on i386: why "rep;nop" ?
On Mon, 17 Sep 2001, Dave Jones wrote:

> On Mon, 17 Sep 2001, Jean-Marc Saffroy wrote:
>
> > What is the intent behind this "rep;nop" ? Does it really rely on an
> > undocumented behaviour ?
>
> Its used to stop Pentium 4's from cooking themselves.
> See the P4 manuals for more info.

Ok, I found it: actually it is the PAUSE opcode in the P4 instruction set,
and the doc for PAUSE mentions that it is equivalent to a NOP on older
IA-32 processors.

So no black magic here, except that "rep;nop" is a bit misleading, since
the Intel docs for REP and NOP do not mention PAUSE...

Thanks all for you help.


Regards,

--
Jean-Marc Saffroy - Research Engineer - Silicomp Research Institute
mailto:saffroy@ri.silicomp.fr

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:03    [from the cache]
©2003-2011 Jasper Spaans. Advertise on this site