PTHREAD_RWLOCK_UNLOCK(3C) Standard C Library Functions

NAME

pthread_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
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 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 scheduling 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 unspecified 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.
Otherwise, an error number is returned to indicate the error.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

pthread_rwlock_init(3C), pthread_rwlock_rdlock(3C),
pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C),
attributes(7), standards(7)

March 23, 2005 PTHREAD_RWLOCK_UNLOCK(3C)