From owner-cvs-src-old@FreeBSD.ORG  Tue Oct  6 13:46:36 2009
Return-Path: <owner-cvs-src-old@FreeBSD.ORG>
Delivered-To: cvs-src-old@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 31AAB1065693
	for <cvs-src-old@freebsd.org>; Tue,  6 Oct 2009 13:46:36 +0000 (UTC)
	(envelope-from attilio@FreeBSD.org)
Received: from repoman.freebsd.org (repoman.freebsd.org
	[IPv6:2001:4f8:fff6::29])
	by mx1.freebsd.org (Postfix) with ESMTP id 1F0838FC12
	for <cvs-src-old@freebsd.org>; Tue,  6 Oct 2009 13:46:36 +0000 (UTC)
Received: from repoman.freebsd.org (localhost [127.0.0.1])
	by repoman.freebsd.org (8.14.3/8.14.3) with ESMTP id n96DkaYD080027
	for <cvs-src-old@freebsd.org>; Tue, 6 Oct 2009 13:46:36 GMT
	(envelope-from attilio@repoman.freebsd.org)
Received: (from svn2cvs@localhost)
	by repoman.freebsd.org (8.14.3/8.14.3/Submit) id n96DkZAn080026
	for cvs-src-old@freebsd.org; Tue, 6 Oct 2009 13:46:35 GMT
	(envelope-from attilio@repoman.freebsd.org)
Message-Id: <200910061346.n96DkZAn080026@repoman.freebsd.org>
X-Authentication-Warning: repoman.freebsd.org: svn2cvs set sender to
	attilio@repoman.freebsd.org using -f
From: Attilio Rao <attilio@FreeBSD.org>
Date: Tue, 6 Oct 2009 13:45:49 +0000 (UTC)
To: cvs-src-old@freebsd.org
X-FreeBSD-CVS-Branch: HEAD
Subject: cvs commit: src/sys/amd64/include atomic.h src/sys/i386/include
 atomic.h
X-BeenThere: cvs-src-old@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: **OBSOLETE** CVS commit messages for the src tree
	<cvs-src-old.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src-old>,
	<mailto:cvs-src-old-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src-old>
List-Post: <mailto:cvs-src-old@freebsd.org>
List-Help: <mailto:cvs-src-old-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src-old>,
	<mailto:cvs-src-old-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 06 Oct 2009 13:46:36 -0000

attilio     2009-10-06 13:45:49 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/include    atomic.h 
    sys/i386/include     atomic.h 
  Log:
  SVN rev 197803 on 2009-10-06 13:45:49Z by attilio
  
  Per their definition, atomic instructions used in conjuction with
  memory barriers should also ensure that the compiler doesn't reorder paths
  where they are used.  GCC, however, does that aggressively, even in
  presence of volatile operands.  The most reliable way GCC offers for avoid
  instructions reordering is clobbering "memory" even if that is
  theoretically an heavy-weight operation, flushing the content of all
  the registers and forcing reload of them (We could rely, however, on
  gcc DTRT by just understanding the purpose as this is a well-known
  pattern for many modern operating-systems).
  
  Not all our memory barriers, right now, clobber memory for GCC-like
  compilers. The most notable cases are IA32 and amd64 where the memory
  barrier are treacted the same as normal atomic instructions.
  Fix this by offering the possibility to implement atomic instructions
  with memory barriers separately from the normal version and implement
  the GCC-like specific one using memory clobbering.
  Thanks to Chris Lattner (@apple) for his discussion on llvm specifics.
  
  Reported by:    jhb
  Reviewed by:    jhb
  Tested by:      rdivacky, Giovanni Trematerra
                  <giovanni dot trematerra at gmail dot com>
  
  Revision  Changes    Path
  1.47      +67 -46    src/sys/amd64/include/atomic.h
  1.52      +73 -46    src/sys/i386/include/atomic.h