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.\"	$NetBSD: sync.2,v 1.15 2003/08/07 16:44:10 agc Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" SUCH DAMAGE.
.\"
.\"     @(#)sync.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt SYNC 2
.Os
.Sh NAME
.Nm sync
.Nd "synchronize disk block in-core status with that on disk"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft void
.Fn sync void
.Sh DESCRIPTION
The
.Fn sync
function forces a write of dirty (modified) buffers
in the block buffer cache out
to disk.
The kernel keeps this information in core to reduce
the number of disk I/O transfers required by the system.
As information in the cache is lost after a system crash,
kernel thread
.Nm ioflush
ensures that dirty buffers are synced to disk
eventually.
By default, a dirty buffer is synced after 30 seconds,
but some filesystems exploit
.Nm ioflush
features to sync directory data and metadata faster
(after 15 and 10 seconds, respectively).
.Pp
The function
.Xr fsync 2
may be used to synchronize individual file descriptor
attributes.
.Sh SEE ALSO
.Xr fsync 2 ,
.Xr sync 8
.Sh HISTORY
A
.Fn sync
function call appeared in
.At v6 .
.Sh BUGS
.Fn sync
may return before the buffers are completely flushed.
d not find a simplier way of dealing with it - Change getpid() and getppid() semantics to match what Linux does, and implement gettid(). In the Linux kernel, threads are implemnted as plain old processes. A thread group is just a set of processes, with the parent called leader. Thread ID, which are returned by gettid(), are just the PID of the plain old processes, and getpid() returns the PID of the thread group leader. - Remove struct linux32_emuldata. COMPAT_LINUX32 uses a lot of COMPAT_LINUX code, where a struct linux_emuldata is assumed. By having distinct emuldata structure with different sizes and layouts, we caused kernel memory corruptions. - Fix setprioriry() and getpriority() Thanks to Nicolas Joly for tracking down the problem and providing me the hardware to fix them. 2006-02-09Add initial (but unfinished) COMPAT_LINUX32 for amd64. This is good enough somanu that the i386 license manager part of amd64 version of Fluent works. While I'm here, add SysV IPC to COMPAT_LINUX/amd64