pthread_rwlock_destroy

Synopsis

#include <pthread.h>

int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);

int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,
                        const pthread_rwlockattr_t *restrict attr);

pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;

Status

Implemented

Conformance

IEEE Std 1003.1-2017

Description

The pthread_rwlock_destroy() function shall destroy the read-write lock object referenced by rwlock and release any resources used by the lock. The effect of subsequent use of the lock is undefined until the lock is reinitialized by another call to pthread_rwlock_init(). 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 behavior.

The pthread_rwlock_init() function shall allocate any resources required to use the read-write lock referenced by rwlock and initialize the lock to an unlocked state with attributes referenced by attr. If attr is NULL, the default read-write lock attributes shall be 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 reinitialized. 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 shall not be initialized and the contents of rwlock 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. The effect shall be equivalent to dynamic initialization by a call to pthread_rwlock_init() with the attr parameter specified as NULL, except that no error checks are performed.

In Phoenix-RTOS a read-write lock is built on a kernel mutex and two kernel condition variables. A lock initialized with PTHREAD_RWLOCK_INITIALIZER allocates them on its first use.

The behavior is undefined if the value specified by the attr argument to pthread_rwlock_init() does not refer to an initialized read-write lock attributes object.

Return value

If successful, the pthread_rwlock_destroy() and pthread_rwlock_init() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors

The pthread_rwlock_init() function shall fail if:

• EAGAIN - The system lacked the necessary resources (other than memory) to initialize another read-write lock.

• ENOMEM - Insufficient memory exists to initialize the read-write lock.

• EPERM - The caller does not have the privilege to perform the operation.

These functions shall not return an error code of EINTR.

POSIX deviations

No POSIX deviations discovered.