pthread_rwlock_unlock man page

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

pthread_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 implementation-defined whether write locks take precedence over read locks.

Results are undefined if this function is 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 shall not return an error code of [EINTR].

The following sections are informative.

Rationale

If an implementation detects that the value specified by the rwlock argument to pthread_rwlock_unlock() does not refer to an initialized read-write lock object, it is recommended that the function should fail and report an [EINVAL] error.

If an implementation detects that the value specified by the rwlock argument to pthread_rwlock_unlock() refers to a read-write lock object for which the current thread does not hold a lock, it is recommended that the function should fail and report an [EPERM] error.

See Also

pthread_rwlock_destroy(), pthread_rwlock_rdlock(), pthread_rwlock_timedrdlock(), pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock()

The Base Definitions volume of POSIX.1‐2008, Section 4.11, Memory Synchronization, <pthread.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual