The pthread_rwlock_trywrlock() function shall apply a write lock like the
pthread_rwlock_wrlock() function, with the exception that the function
shall fail if any thread currently holds rwlock (for reading or
The pthread_rwlock_wrlock() function shall apply a write lock to the
read-write lock referenced by rwlock. The calling thread acquires the
write lock if no other thread (reader or writer) holds the read-write lock
rwlock. Otherwise, the thread shall block until it can acquire the
lock. The calling thread may deadlock if at the time the call is made it holds
the read-write lock (whether a read or write lock).
Implementations may favor writers over readers to avoid writer starvation.
Results are undefined if any of these functions are called with an uninitialized
If a signal is delivered to a thread waiting for a read-write lock for writing,
upon return from the signal handler the thread resumes waiting for the
read-write lock for writing as if it was not interrupted.
The pthread_rwlock_trywrlock() function shall return zero if the lock for
writing on the read-write lock object referenced by rwlock is acquired.
Otherwise, an error number shall be returned to indicate the error.
If successful, the pthread_rwlock_wrlock() function shall return zero;
otherwise, an error number shall be returned to indicate the error.
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