PTHREAD_RWLOCK_UNLOCK(P) POSIX Programmer's Manual PTHREAD_RWLOCK_UNLOCK(P)NAMEpthread_rwlock_unlock - unlock a read-write lock object
SYNOPSIS
#include <pthread.h>
int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
DESCRIPTION
The pthread_rwlock_unlock() function shall release a lock held on the
read-write lock object referenced by rwlock. Results are undefined if
the read-write lock rwlock is not held by the calling thread.
If this function is called to release a read lock from the read-write
lock object and there are other read locks currently held on this read-
write lock object, the read-write lock object remains in the read
locked state. If this function releases the last read lock for this
read-write lock object, the read-write lock object shall be put in the
unlocked state with no owners.
If this function is called to release a write lock for this read-write
lock object, the read-write lock object shall be put in the unlocked
state.
If there are threads blocked on the lock when it becomes available, the
scheduling policy shall determine which thread(s) shall acquire the
lock. If the Thread Execution Scheduling option is supported, when
threads executing with the scheduling policies SCHED_FIFO, SCHED_RR, or
SCHED_SPORADIC are waiting on the lock, they shall acquire the lock in
priority order when the lock becomes available. For equal priority
threads, write locks shall take precedence over read locks. If the
Thread Execution Scheduling option is not supported, it is implementa‐
tion-defined whether write locks take precedence over read locks.
Results are undefined if any of these functions are called with an
uninitialized read-write lock.
RETURN VALUE
If successful, the pthread_rwlock_unlock() function shall return zero;
otherwise, an error number shall be returned to indicate the error.
ERRORS
The pthread_rwlock_unlock() function may fail if:
EINVAL The value specified by rwlock does not refer to an initialized
read-write lock object.
EPERM The current thread does not hold a lock on the read-write lock.
The pthread_rwlock_unlock() function shall not return an error code of
[EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOpthread_rwlock_destroy() , pthread_rwlock_rdlock() ,
pthread_rwlock_timedrdlock() , pthread_rwlock_timedwrlock() ,
pthread_rwlock_tryrdlock() , pthread_rwlock_trywrlock() ,
pthread_rwlock_wrlock() , the Base Definitions volume of
IEEE Std 1003.1-2001, <pthread.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 PTHREAD_RWLOCK_UNLOCK(P)
