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kstat(9s) [sunos man page]

kstat(9S)						    Data Structures for Drivers 						 kstat(9S)

kstat - kernel statistics structure SYNOPSIS
#include <sys/types.h> #include <sys/kstat.h> #include <sys/ddi.h> #include <sys/sunddi.h> INTERFACE LEVEL
Solaris DDI specific (Solaris DDI) DESCRIPTION
Each kernel statistic (kstat) exported by device drivers consists of a header section and a data section. The kstat structure is the header portion of the statistic. A driver receives a pointer to a kstat structure from a successful call to kstat_create(9F). Drivers should never allocate a kstat struc- ture in any other manner. After allocation, the driver should perform any further initialization needed before calling kstat_install(9F) to actually export the kstat. STRUCTURE MEMBERS
void *ks_data; /* kstat type-specific data */ ulong_t ks_ndata; /* # of type-specific data records */ ulong_t ks_data_size; /* total size of kstat data section */ int (*ks_update)(struct kstat *, int); void *ks_private; /* arbitrary provider-private data */ void *ks_lock; /* protects this kstat's data */ The members of the kstat structure available to examine or set by a driver are as follows: ks_data Points to the data portion of the kstat. Either allocated by kstat_create(9F) for the drivers use, or by the driver if it is using virtual kstats. ks_ndata The number of data records in this kstat. Set by the ks_update(9E) routine. ks_data_size The amount of data pointed to by ks_data. Set by the ks_update(9E) routine. ks_update Pointer to a routine that dynamically updates kstat. This is useful for drivers where the underlying device keeps cheap hardware statistics, but where extraction is expensive. Instead of constantly keeping the kstat data section up to date, the driver can supply a ks_update(9E) function that updates the kstat data section on demand. To take advantage of this feature, set the ks_update field before calling kstat_install(9F). ks_private Is a private field for the driver's use. Often used in ks_update(9E). ks_lock Is a pointer to a mutex that protects this kstat. kstat data sections are optionally protected by the per-kstat ks_lock. If ks_lock is non-NULL, kstat clients (such as /dev/kstat) will acquire this lock for all of their operations on that kstat. It is up to the kstat provider to decide whether guaranteeing consistent data to kstat clients is sufficiently important to justify the locking cost. Note, however, that most statistic updates already occur under one of the provider's mutexes. If the provider sets ks_lock to point to that mutex, then kstat data locking is free. ks_lock is really of type (kmutex_t*) and is declared as (void*) in the kstat header. That way, users do not have to be exposed to all of the kernel's lock- related data structures. SEE ALSO
kstat_create(9F) Writing Device Drivers SunOS 5.10 4 Apr 1994 kstat(9S)

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kstat_chain_update(3KSTAT)				Kernel Statistics Library Functions				kstat_chain_update(3KSTAT)

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 delete old ones as various device instances are added and removed, thereby caus- ing 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. 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. Other- wise, 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) SunOS 5.11 3 Aug 2004 kstat_chain_update(3KSTAT)
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