'\" te
.\" Copyright (c) 2004, Sun Microsystems, Inc. All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH KSTAT_CHAIN_UPDATE 3KSTAT "Aug 3, 2004"
.SH NAME
kstat_chain_update \- update the kstat header chain
.SH SYNOPSIS
.nf
\fBcc\fR [ \fIflag\fR\&.\|.\|. ] \fIfile\fR\&.\|.\|. \fB-lkstat\fR [ \fIlibrary\fR\&.\|.\|.]
#include <kstat.h>



\fBkid_t\fR \fBkstat_chain_update\fR(\fBkstat_ctl_t *\fR\fIkc\fR);
.fi

.SH DESCRIPTION
The \fBkstat_chain_update()\fR function brings the user's kstat header chain in
sync with that of the kernel. The kstat chain is a linked list of kstat headers
(\fBkstat_t\fR's) pointed to by \fIkc\fR->\fBkc_chain\fR, which is initialized
by \fBkstat_open\fR(3KSTAT). This chain constitutes a list of all kstats
currently in the system.
.sp
.LP
During normal operation, the kernel creates new kstats and deletes old ones as
various device instances are added and removed, thereby causing the user's copy
of the kstat chain to become out of date. The \fBkstat_chain_update()\fR
function detects this condition by comparing the kernel's current kstat chain
ID (KCID), which is incremented every time the kstat chain changes, to the
user's KCID, \fIkc\fR->\fBkc_chain_id\fR. If the KCIDs match,
\fBkstat_chain_update()\fR does nothing.  Otherwise, it deletes any invalid
kstat headers from the user's kstat chain, adds any new ones, and sets
\fIkc\fR->\fBkc_chain_id\fR to the new KCID. All other kstat headers in the
user's kstat chain are unmodified.
.sp
.LP
Because of the deletion process, any \fBkstat_t\fR structures retrieved by the
\fBkstat_lookup\fR(3KSTAT) function or data pointers obtained through the
\fBkstat_data_lookup\fR(3KSTAT) function are invalidated by a call to
\fRkstat_chain_update\fB(). New lookup calls must be made to obtain fresh
structures after each chain update.
.SH RETURN VALUES
Upon successful completion, \fBkstat_chain_update()\fR returns the new KCID if
the kstat chain has changed and 0 if it has not changed. Otherwise, it returns
\(mi1 and sets \fBerrno\fR to indicate the error.
.SH ERRORS
The \fBkstat_chain_update()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 13n
The kstat was temporarily unavailable for reading or writing.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 13n
Insufficient storage space is available.
.RE

.sp
.ne 2
.na
\fB\fBENXIO\fR\fR
.ad
.RS 13n
The given kstat could not be located for reading.
.RE

.sp
.ne 2
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
The data for the given kstat was too large to be stored in the structure.
.RE

.SH FILES
.ne 2
.na
\fB\fB/dev/kstat\fR\fR
.ad
.RS 14n
kernel statistics driver
.RE

.SH ATTRIBUTES
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Stable
_
MT-Level	Unsafe
.TE

.SH SEE ALSO
\fBkstat\fR(3KSTAT), \fBkstat_lookup\fR(3KSTAT), \fBkstat_open\fR(3KSTAT),
\fBkstat_read\fR(3KSTAT), \fBattributes\fR(5)