pthread_rwlock_init(3T) pthread_rwlock_init(3T)
NAME
pthread_rwlock_init(), pthread_rwlock_destroy() - initialize or destroy a read-write lock
SYNOPSIS
PARAMETERS
rwlock Pointer to the read-write lock to be initialized or destroyed.
attr Pointer to the attributes object that defines the characteristics of the read-write lock to be initialized. If the
pointer is NULL, default attributes are used.
DESCRIPTION
initializes the read-write lock referenced by rwlock with the attributes attr. If attr is NULL, the default read-write lock attributes are
used. Upon successful initialization, the state of the read-write lock becomes initialized and unlocked. Attempting to initialize an
already initialized read-write lock object results in undefined behavior.
The macro can be used to initialize read-write locks which are statically allocated. The effect is equivalent to dynamic initialization by
a call to with the attr parameter specified as NULL, except that no error checks are performed. The read-write lock will be initialized
with default attributes.
If the process-shared attribute in the read-write lock attributes object referenced by attr is defined as the read-write lock must be allo-
cated such that the processes sharing the read-write lock has access to it. This may be done through the memory-mapping functions (see
mmap(2)) or shared memory functions (see shmget(2)).
destroys the read-write referenced by rwlock. This function may set rwlock to an invalid value. The destroyed read-write lock can be
reinitialized using the function If the read-write lock is referenced after destruction in any read-write lock call, the resulting behavior
is undefined.
A read-write lock should be destroyed only when no threads are currently using it. Destroying a read-write lock which is currently in use
results in undefined behavior.
RETURN VALUE
Upon successful completion, and returns zero. Otherwise, an error number is returned to indicate the error (the variable is not set).
ERRORS
If any of the following occur, the function returns the corresponding error number:
The necessary resources (other than memory) to initialize
rwlock are not available.
rwlock is an already initialized read-write lock. However, getting for reinitializing the rwlock cannot be expected all the
time since the behavior of reinitializing the rwlock is undefined.
The value specified by
rwlock or attr is invalid.
There is insufficient memory available in which to initialize the
read-write lock rwlock.
The caller does not have the privilege to perform the operation.
If any of the following occur, the function returns the corresponding error number:
rwlock is currently locked or being used by other threads.
The value specified by
rwlock is invalid.
WARNINGS
The space for the read-write lock must to be allocated before calling Undefined behavior may result if the process-shared attribute of attr
is and the space allocated for the read-write lock is not accessible to cooperating threads.
AUTHOR
and were developed by X/Open.
SEE ALSO
pthread_rwlock_rdlock(3T), pthread_rwlock_tryrdlock(3T), pthread_rwlock_trywrlock(3T), pthread_rwlock_unlock(3T),
pthread_rwlock_wrlock(3T).
STANDARDS CONFORMANCE
Pthread Library pthread_rwlock_init(3T)