PTHREAD_RWLOCK_WRLOCK(3)  OpenBSD Programmer's Manual PTHREAD_RWLOCK_WRLOCK(3)

NAME
     pthread_rwlock_wrlock, pthread_rwlock_trywrlock - acquire a read/write
     lock for writing



SYNOPSIS
     #include <pthread.h>

     int
     pthread_rwlock_wrlock(pthread_rwlock_t *lock);

     int
     pthread_rwlock_trywrlock(pthread_rwlock_t *lock);

DESCRIPTION
     The pthread_rwlock_wrlock() function blocks until a write lock can be ac-
     quired against lock. The pthread_rwlock_trywrlock() function performs the
     same action, but does not block if the lock cannot be immediately ob-
     tained.

     The results are undefined if the calling thread already holds the lock at
     the time the call is made.

IMPLEMENTATION NOTES
     To prevent writer starvation, writers are favored over readers.

RETURN VALUES
     If successful, the pthread_rwlock_wrlock() and pthread_rwlock_trywrlock()
     functions will return zero.  Otherwise an error number will be returned
     to indicate the error.

SEE ALSO
     pthread_rwlock_trywrlock(3),  pthread_rwlock_unlock(3),
     pthread_rwlock_wrlock(3)

STANDARDS
     The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions are
     expected to conform to Version 2 of the Single UNIX Specification.

ERRORS
     The pthread_rwlock_trywrlock() function will fail if:

     [EBUSY]       The calling thread is not able to acquire the lock without
                   blocking.

     The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions may
     fail if:

     [EDEADLK]     The calling thread already owns the read/write lock (for
                   reading or writing).

     [EINVAL]      The value specified by lock is invalid.

     [ENOMEM]      Insufficient memory exists to initialize the lock (applies
                   to statically initialized locks only).

HISTORY
     The pthread_rwlock_wrlock() function first appeared in OpenBSD 2.5.

OpenBSD 2.6                     August 4, 1998                               1