.\" $NetBSD: __insn_barrier.3,v 1.4 2017/11/13 09:11:16 wiz Exp $ .\" .\" Copyright (c) 2010 Jukka Ruohonen <jruohonen@iki.fi> .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd January 2, 2011 .Dt __INSN_BARRIER 3 .Os .Sh NAME .Nm __insn_barrier .Nd compiler reorder barrier .Sh SYNOPSIS .In sys/cdefs.h .Ft void .Fn __insn_barrier .Sh DESCRIPTION The .Fn __insn_barrier macro prevents GCC from moving code across the barrier. In other words, the compiler is not allowed to reorder read and write commands below the barrier with the code preceding the barrier. Like with the .Em volatile type qualifier, .Fn __insn_barrier may be necessary in some corner cases to prevent the compiler from misoptimizing. .Sh SEE ALSO .Xr gcc 1 , .Xr cdefs 3 , .Xr membar_ops 3 .Rs .%A Paul E. McKenney .%T Memory Barriers: a Hardware View for Software Hackers .%D June 7, 2010 .%U http://www.rdrop.com/users/paulmck/scalability/paper/whymb.2010.06.07c.pdf .Re .Sh HISTORY The .Fn __insn_barrier macro first appeared in .Nx 2.0 . |