1.\" $NetBSD: msync.2,v 1.18 2002/08/11 14:44:33 yamt Exp $ 2.\" 3.\" Copyright (c) 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)msync.2 8.2 (Berkeley) 6/21/94 35.\" 36.Dd August 11, 2002 37.Dt MSYNC 2 38.Os 39.Sh NAME 40.Nm msync 41.Nd synchronize a mapped region 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]sys/mman.h\*[Gt] 46.Ft int 47.Fn msync "void *addr" "size_t len" "int flags" 48.Sh DESCRIPTION 49The 50.Fn msync 51system call writes all pages with shared modifications 52in the specified 53region of the process's address space back to permanent 54storage, and, if requested, invalidates cached data mapped 55in the region. 56If 57.Fa len 58is 0, all modified pages within the region containing 59.Fa addr 60will be flushed; 61if 62.Fa len 63is non-zero, only modified pages containing 64.Fa addr 65and 66.Fa len 67succeeding locations will be flushed. 68Any required synchronization of memory caches 69will also take place at this time. 70Filesystem operations on a file that is mapped for shared modifications 71are unpredictable except after an 72.Fn msync . 73.Pp 74The 75.Fa flags 76argument is formed by 77.Em or Ns 'ing 78the following values 79.Pp 80.Bl -column -offset indent -compact MS_INVALIDATE 81.It Dv MS_ASYNC Ta Perform asynchronous writes. 82.It Dv MS_SYNC Ta Perform synchronous writes. 83.It Dv MS_INVALIDATE Ta Invalidate cached data after writing. 84.El 85.Sh RETURN VALUES 86Upon successful completion, 87a value of 0 is returned. 88Otherwise, a value of -1 is returned and 89.Va errno 90is set to indicate the error. 91.Sh ERRORS 92The following errors may be reported: 93.Bl -tag -width Er 94.It Bq Er EBUSY 95The 96.Dv MS_INVALIDATE 97flag was specified and a portion of the specified region 98was locked with 99.Xr mlock 2 . 100.It Bq Er EINVAL 101The specified 102.Fa flags 103argument was invalid. 104.It Bq Er EINVAL 105The 106.Fa addr 107parameter was not page aligned. 108.It Bq Er EINVAL 109The 110.Fa addr 111parameter did not specify an address part of a mapped region. 112.It Bq Er EINVAL 113The 114.Fa len 115parameter was negative. 116.It Bq Er EIO 117An I/O error occurred while writing to the file system. 118.It Bq Er ENOMEM 119Addresses in the specified region are outside the range allowed 120for the address space of the process, or specify one or more pages 121which are unmapped. 122.El 123.Sh SEE ALSO 124.Xr mlock 2 , 125.Xr mmap 2 , 126.Xr munlock 2 127.Sh HISTORY 128The 129.Fn msync 130function first appeared in 131.Bx 4.4 . 132It was modified to conform to 133.St -p1003.1b-93 134in 135.Nx 1.3 . 136.Sh BUGS 137Writes are currently done synchronously even if the 138.Dv MS_ASYNC 139flag is specified. 140