| PTHREAD_RWLOCK(3) | Library Functions Manual | PTHREAD_RWLOCK(3) | 
pthread_rwlock,
  pthread_rwlock_init,
  pthread_rwlock_destroy,
  pthread_rwlock_rdlock,
  pthread_rwlock_timedrdlock,
  pthread_rwlock_tryrdlock,
  pthread_rwlock_wrlock,
  pthread_rwlock_timedwrlock,
  pthread_rwlock_trywrlock,
  pthread_rwlock_unlock —
#include <pthread.h>
int
  
  pthread_rwlock_init(pthread_rwlock_t
    * restrict lock, const
    pthread_rwlockattr_t * restrict attr);
pthread_rwlock_t lock =
    PTHREAD_RWLOCK_INITIALIZER;
int
  
  pthread_rwlock_destroy(pthread_rwlock_t
    *lock);
int
  
  pthread_rwlock_rdlock(pthread_rwlock_t
    *lock);
int
  
  pthread_rwlock_timedrdlock(pthread_rwlock_t
    * restrict lock, const
    struct timespec * restrict abstime);
int
  
  pthread_rwlock_tryrdlock(pthread_rwlock_t
    *lock);
int
  
  pthread_rwlock_wrlock(pthread_rwlock_t
    *lock);
int
  
  pthread_rwlock_timedwrlock(pthread_rwlock_t
    * restrict lock, const
    struct timespec * restrict abstime);
int
  
  pthread_rwlock_trywrlock(pthread_rwlock_t
    *lock);
int
  
  pthread_rwlock_unlock(pthread_rwlock_t
    *lock);
pthread_rwlock_init() function is used to initialize
  a read/write lock, with attributes specified by attr. If
  attr is NULL, the default
  read/write lock attributes are used.
The results of calling
    pthread_rwlock_init() with an already initialized
    lock are undefined.
The macro PTHREAD_RWLOCK_INITIALIZER can
    be used to initialize a read/write lock when the allocation can be done
    statically, no error checking is required, and the default attributes are
    appropriate. The behavior is similar to calling
    pthread_rwlock_init() with
    attr specified as NULL.
The pthread_rwlock_destroy() function is
    used to destroy a read/write lock previously created with
    pthread_rwlock_init().
The pthread_rwlock_rdlock() function
    acquires a read lock on lock provided that
    lock is not presently held for writing and no writer
    threads are presently blocked on the lock. If the read lock cannot be
    immediately acquired, the calling thread blocks until it can acquire the
    lock.
The pthread_rwlock_timedrdlock() performs
    the same action, but will not wait beyond abstime to
    obtain the lock before returning.
The pthread_rwlock_tryrdlock() function
    performs the same action as pthread_rwlock_rdlock(),
    but does not block if the lock cannot be immediately obtained (i.e., the
    lock is held for writing or there are waiting writers).
A thread may hold multiple concurrent read locks. If so,
    pthread_rwlock_unlock() must be called once for each
    lock obtained.
The results of acquiring a read lock while the calling thread holds a write lock are undefined.
The pthread_rwlock_wrlock() function
    blocks until a write lock can be acquired against
    lock.
The pthread_rwlock_timedwrlock() performs
    the same action, but will not wait beyond abstime to
    obtain the lock before returning.
The pthread_rwlock_trywrlock() function
    performs the same action as pthread_rwlock_wrlock(),
    but does not block if the lock cannot be immediately obtained.
The results are undefined if the calling thread already holds the lock at the time the call is made.
The pthread_rwlock_unlock() function is
    used to release the read/write lock previously obtained by
    pthread_rwlock_rdlock(),
    pthread_rwlock_wrlock(),
    pthread_rwlock_tryrdlock(), or
    pthread_rwlock_trywrlock().
pthread_rwlock_init() function will
  return zero. Otherwise an error number will be returned to indicate the error.
If successful, the
    pthread_rwlock_destroy(),
    pthread_rwlock_rdlock(),
    pthread_rwlock_timedrdlock(),
    pthread_rwlock_tryrdlock(),
    pthread_rwlock_wrlock(),
    pthread_rwlock_timedwrlock(),
    pthread_rwlock_trywrlock(), and
    pthread_rwlock_unlock() will return zero. Otherwise
    an error number will be returned to indicate the error.
The results are undefined if lock is not held by the calling thread.
pthread_rwlock_init() function may fail if:
EAGAIN]EBUSY]EINVAL]ENOMEM]The pthread_rwlock_destroy() function may
    fail if:
EBUSY]EINVAL]The pthread_rwlock_tryrdlock() function
    shall fail if:
EBUSY]The pthread_rwlock_timedrdlock() function
    shall fail if:
ETIMEDOUT]The pthread_rwlock_rdlock(),
    pthread_rwlock_timedrdlock(), and
    pthread_rwlock_tryrdlock() functions may fail
  if:
EAGAIN]EDEADLK]EINVAL]The pthread_rwlock_trywrlock() function
    shall fail if:
EBUSY]The pthread_rwlock_timedrdlock() function
    shall fail if:
ETIMEDOUT]The pthread_rwlock_wrlock(),
    pthread_rwlock_timedwrlock(), and
    pthread_rwlock_trywrlock() functions may fail
  if:
EDEADLK]EINVAL]The pthread_rwlock_unlock() function may
    fail if:
PTHREAD_PROCESS_SHARED attribute is not supported.
| July 8, 2010 | NetBSD 10.0 |