136 lines
3.9 KiB
Groff
136 lines
3.9 KiB
Groff
.\" $NetBSD: msync.2,v 1.21 2003/08/07 16:44:02 agc Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)msync.2 8.2 (Berkeley) 6/21/94
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.\"
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.Dd August 11, 2002
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.Dt MSYNC 2
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.Os
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.Sh NAME
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.Nm msync
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.Nd synchronize a mapped region
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft int
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.Fn msync "void *addr" "size_t len" "int flags"
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.Sh DESCRIPTION
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The
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.Fn msync
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system call writes all pages with shared modifications
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in the specified
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region of the process's address space back to permanent
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storage, and, if requested, invalidates cached data mapped
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in the region.
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If
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.Fa len
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is 0, all modified pages within the region containing
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.Fa addr
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will be flushed;
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if
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.Fa len
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is non-zero, only modified pages containing
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.Fa addr
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and
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.Fa len
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succeeding locations will be flushed.
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Any required synchronization of memory caches
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will also take place at this time.
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Filesystem operations on a file that is mapped for shared modifications
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are unpredictable except after an
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.Fn msync .
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.Pp
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The
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.Fa flags
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argument is formed by
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.Em or Ns 'ing
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the following values
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.Pp
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.Bl -column -offset indent -compact MS_INVALIDATE
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.It Dv MS_ASYNC Ta Perform asynchronous writes.
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.It Dv MS_SYNC Ta Perform synchronous writes.
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.It Dv MS_INVALIDATE Ta Invalidate cached data after writing.
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.El
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.Sh RETURN VALUES
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Upon successful completion,
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a value of 0 is returned.
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Otherwise, a value of -1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The following errors may be reported:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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The
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.Dv MS_INVALIDATE
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flag was specified and a portion of the specified region
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was locked with
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.Xr mlock 2 .
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.It Bq Er EINVAL
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The specified
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.Fa flags
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argument was invalid.
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.It Bq Er EINVAL
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The
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.Fa addr
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parameter was not page aligned.
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.It Bq Er EINVAL
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The
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.Fa addr
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parameter did not specify an address part of a mapped region.
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.It Bq Er EINVAL
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The
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.Fa len
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parameter was negative.
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.It Bq Er EIO
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An I/O error occurred while writing to the file system.
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.It Bq Er ENOMEM
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Addresses in the specified region are outside the range allowed
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for the address space of the process, or specify one or more pages
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which are unmapped.
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.El
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.Sh SEE ALSO
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.Xr mlock 2 ,
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.Xr mmap 2 ,
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.Xr munlock 2
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.Sh HISTORY
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The
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.Fn msync
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function first appeared in
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.Bx 4.4 .
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It was modified to conform to
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.St -p1003.1b-93
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in
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.Nx 1.3 .
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.Sh BUGS
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Writes are currently done synchronously even if the
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.Dv MS_ASYNC
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flag is specified.
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