fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
127 lines
3.5 KiB
Groff
127 lines
3.5 KiB
Groff
.\" 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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.\" $FreeBSD$
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.\"
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.Dd March 18, 2012
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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
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writes any modified pages back to the file system and updates
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the file modification time.
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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 those pages containing
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.Fa addr
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and
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.Fa len-1
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succeeding locations will be examined.
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The
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.Fa flags
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argument may be specified as follows:
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.Pp
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.Bl -tag -width ".Dv MS_INVALIDATE" -compact
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.It Dv MS_ASYNC
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Return immediately
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.It Dv MS_SYNC
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Perform synchronous writes
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.It Dv MS_INVALIDATE
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Invalidate all cached data
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.El
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.Sh RETURN VALUES
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.Rv -std msync
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.Sh ERRORS
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The
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.Fn msync
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBUSY
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Some or all of the pages in the specified region are locked and
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.Dv MS_INVALIDATE
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is specified.
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.It Bq Er EINVAL
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The
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.Fa addr
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argument
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is not a multiple of the hardware page size.
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.It Bq Er ENOMEM
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The addresses in the range starting at
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.Fa addr
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and continuing for
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.Fa len
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bytes are outside the range allowed for the address space of a
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process or specify one or more pages that are not mapped.
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.It Bq Er EINVAL
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The
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.Fa flags
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argument
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was both MS_ASYNC and MS_INVALIDATE.
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Only one of these flags is allowed.
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.It Bq Er EIO
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An error occurred while writing at least one of the pages in
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the specified region.
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.El
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.Sh SEE ALSO
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.Xr madvise 2 ,
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.Xr mincore 2 ,
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.Xr mlock 2 ,
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.Xr mprotect 2 ,
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.Xr munmap 2
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.Sh HISTORY
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The
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.Fn msync
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system call first appeared in
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.Bx 4.4 .
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.Sh BUGS
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The
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.Fn msync
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system call is usually not needed since
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.Bx
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implements a coherent file system buffer cache.
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However, it may be used to associate dirty VM pages with file system
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buffers and thus cause them to be flushed to physical media sooner
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rather than later.
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