man/man3kstat/kstat_chain_update.3kstat

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 KSTAT_CHAIN_UPDATE 3KSTAT "Aug 3, 2004"
 NAME
kstat_chain_update - update the kstat header chain
 SYNOPSIS
cc [ flag.\|.\|. ] file.\|.\|. -lkstat [ library.\|.\|.]
#include <kstat.h>


kid_t kstat_chain_update(kstat_ctl_t *kc);


 DESCRIPTION
The kstat_chain_update() 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
(kstat_t's) pointed to by kc->kc_chain, which is initialized
by kstat_open(3KSTAT). This chain constitutes a list of all kstats
currently in the system.

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of the kstat chain to become out of date.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 kstat_chain_update()
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, kc->kc_chain_id. If the KCIDs match,
kstat_chain_update() does nothing. Otherwise, it deletes any invalid
kstat headers from the user's kstat chain, adds any new ones, and sets
kc->kc_chain_id to the new KCID. All other kstat headers in the
user's kstat chain are unmodified.

Because of the deletion process, any kstat_t structures retrieved by the
kstat_lookup(3KSTAT) function or data pointers obtained through the
kstat_data_lookup(3KSTAT) function are invalidated by a call to
kstat_chain_update(). New lookup calls must be made to obtain fresh
structures after each chain update.
 RETURN VALUES
Upon successful completion, kstat_chain_update() returns the new KCID if
the kstat chain has changed and 0 if it has not changed. Otherwise, it returns
-1 and sets errno to indicate the error.
 ERRORS
The kstat_chain_update() function will fail if:
EAGAIN

The kstat was temporarily unavailable for reading or writing.


ENOMEM

Insufficient storage space is available.


ENXIO

The given kstat could not be located for reading.


EOVERFLOW

The data for the given kstat was too large to be stored in the structure.


 FILES
/dev/kstat

kernel statistics driver


 ATTRIBUTES
See attributes(5) for descriptions of the following attributes:


ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Stable
MT-Level Unsafe


 SEE ALSO
kstat(3KSTAT), kstat_lookup(3KSTAT), kstat_open(3KSTAT),
kstat_read(3KSTAT), attributes(5)