PTHREAD_RWLOCK_UNLOCK(3C)PTHREAD_RWLOCK_UNLOCK(3C)NAMEpthread_rwlock_unlock - unlock read-write lock object
SYNOPSIS
cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>
int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
DESCRIPTION
The pthread_rwlock_unlock() function is called to release a lock held
on the read-write lock object referenced by rwlock. Results are unde‐
fined 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 calling thread's last read
lock on this read-write lock object, then the calling thread is no
longer one of the owners of the object. If this function releases the
last read lock for this read-write lock object, the read-write lock
object will 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 will be put in the unlocked
state with no owners.
If the call to the pthread_rwlock_unlock() function results in the
read-write lock object becoming unlocked and there are multiple threads
waiting to acquire the read-write lock object for writing, the schedul‐
ing policy is used to determine which thread acquires the read-write
lock object for writing. If there are multiple threads waiting to
acquire the read-write lock object for reading, the scheduling policy
is used to determine the order in which the waiting threads acquire the
read-write lock object for reading. If there are multiple threads
blocked on rwlock for both read locks and write locks, it is unspeci‐
fied whether the readers acquire the lock first or whether a writer
acquires the lock first.
Results are undefined if any of these functions are called with an
uninitialized read-write lock.
RETURN VALUES
If successful, the pthread_rwlock_unlock() function returns 0. Other‐
wise, an error number is returned to indicate the error.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
├────────────────────┼─────────────────┤
│MT-Level │ MT-Safe │
└────────────────────┴─────────────────┘
SEE ALSOpthread_rwlock_init(3C), pthread_rwlock_rdlock(3C),
pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C), attributes(5),
standards(5)
Mar 23, 2005 PTHREAD_RWLOCK_UNLOCK(3C)
