14bb07bf2a
documenting the obsoleteness of the msync(2) syscall and its single remaining purpose. PR: 70916 Submitted by: Radim Kolar <hsn@netmag.cz> MFC after: 3 days
126 lines
3.5 KiB
Groff
126 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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 June 21, 1994
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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 EINVAL
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The
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.Fa len
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argument
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is too large or negative.
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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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.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 obsolete 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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