pthread_rwlock_init(3C) Standard C Library Functions pthread_rwlock_init(3C)NAME
pthread_rwlock_init, pthread_rwlock_destroy - initialize or destroy
read-write lock object
SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>
int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock, const
pthread_rwlockattr_t *restrict attr);
int pthread_rwlock_destroy(pthread_rwlock_t **rwlock);
pthread_rwlock_t rwlock=PTHREAD_RWLOCK_INITIALIZER;
DESCRIPTION
The pthread_rwlock_init() function initializes the read-write lock ref‐
erenced by rwlock with the attributes referenced by attr. If attr is
NULL, the default read-write lock attributes are used; the effect is
the same as passing the address of a default read-write lock
attributes object. Once initialized, the lock can be used any number
of times without being re-initialized. Upon successful initialization,
the state of the read-write lock becomes initialized and unlocked.
Results are undefined if pthread_rwlock_init() is called specifying an
already initialized read-write lock. Results are undefined if a read-
write lock is used without first being initialized.
If the pthread_rwlock_init() function fails, rwlock is not initialized
and the contents of rwlock are undefined.
The pthread_rwlock_destroy() function destroys the read-write lock
object referenced by rwlock and releases any resources used by the
lock. The effect of subsequent use of the lock is undefined until the
lock is re-initialized by another call to pthread_rwlock_init(). An
implementation may cause pthread_rwlock_destroy() to set the object
referenced by rwlock to an invalid value. Results are undefined if
pthread_rwlock_destroy() is called when any thread holds rwlock.
Attempting to destroy an uninitialized read-write lock results in
undefined behaviour. A destroyed read-write lock object can be re-ini‐
tialized using pthread_rwlock_init(); the results of otherwise refer‐
encing the read-write lock object after it has been destroyed are
undefined.
In cases where default read-write lock attributes are appropriate, the
macro PTHREAD_RWLOCK_INITIALIZER can be used to initialize read-write
locks that are statically allocated. The effect is equivalent to
dynamic initialization by a call to pthread_rwlock_init() with the
parameter attr specified as NULL, except that no error checks are per‐
formed.
RETURN VALUES
If successful, the pthread_rwlock_init() and pthread_rwlock_destroy()
functions return 0. Otherwise, an error number is returned to indi‐
cate the error.
ERRORS
The pthread_rwlock_init() and pthread_rwlock_destroy() functions will
fail if:
EINVAL The value specified by attr is invalid.
EINVAL The value specified by rwlock is invalid.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOpthread_rwlock_rdlock(3C), pthread_rwlock_unlock(3C),
pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C), attributes(5),
standards(5)SunOS 5.10 23 mar 2005 pthread_rwlock_init(3C)
