1.\" $OpenBSD: msync.2,v 1.23 2014/07/02 22:22:35 matthew Exp $ 2.\" $NetBSD: msync.2,v 1.8 1995/10/12 15:41:09 jtc Exp $ 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)msync.2 8.1 (Berkeley) 6/9/93 32.\" 33.Dd $Mdocdate: July 2 2014 $ 34.Dt MSYNC 2 35.Os 36.Sh NAME 37.Nm msync 38.Nd synchronize a mapped region 39.Sh SYNOPSIS 40.In sys/mman.h 41.Ft int 42.Fn msync "void *addr" "size_t len" "int flags" 43.Sh DESCRIPTION 44The 45.Fn msync 46system call writes all pages with shared modifications 47in the specified 48region of the process's address space back to permanent 49storage, and, if requested, invalidates cached data mapped 50in the region. 51If 52.Fa len 53is 0, all modified pages within the region containing 54.Fa addr 55will be flushed; 56if 57.Fa len 58is non-zero, only modified pages containing 59.Fa addr 60and 61.Fa len-1 62succeeding locations will be flushed. 63Any required synchronization of memory caches 64will also take place at this time. 65Filesystem operations on a file that is mapped for shared modifications 66are unpredictable except after an 67.Fn msync . 68.Pp 69The 70.Fa flags 71argument is the bitwise OR of zero or more of the following values: 72.Bd -literal -offset indent 73MS_ASYNC Perform asynchronous writes. 74MS_SYNC Perform synchronous writes. 75MS_INVALIDATE Invalidate cached data after writing. 76.Ed 77.Sh RETURN VALUES 78.Rv -std 79.Sh ERRORS 80The following errors may be reported: 81.Bl -tag -width Er 82.It Bq Er EBUSY 83The 84.Dv MS_INVALIDATE 85flag was specified and a portion of the specified region 86was locked with 87.Xr mlock 2 . 88.It Bq Er EINVAL 89The specified 90.Fa flags 91argument was invalid. 92.It Bq Er EINVAL 93The 94.Fa addr 95parameter was not page aligned or 96.Fa addr 97and 98.Fa size 99specify a region that would extend beyond the end of the address space. 100.It Bq Er ENOMEM 101Addresses in the specified region are outside the range allowed 102for the address space of the process, or specify one or more pages 103which are unmapped. 104.It Bq Er EIO 105An I/O error occurred while writing. 106.El 107.Sh SEE ALSO 108.Xr madvise 2 , 109.Xr mincore 2 , 110.Xr minherit 2 , 111.Xr mprotect 2 , 112.Xr munmap 2 113.Sh HISTORY 114The 115.Fn msync 116function first appeared in 117.Bx 4.4 . 118It was modified to conform to 119.St -p1003.1b-93 120.Sh BUGS 121Writes are currently done synchronously even if the 122.Dv MS_ASYNC 123flag is specified. 124