PTHREAD_RWLOCK_TRYWRLOCK(P) POSIX Programmer's Manual PTHREAD_RWLOCK_TRYWRLOCK(P)
pthread_rwlock_trywrlock, pthread_rwlock_wrlock - lock a read-write lock object for writ-
int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
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 writing).
The pthread_rwlock_wrlock() function shall apply a write lock to the read-write lock ref-
erenced 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 read-
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.
The pthread_rwlock_trywrlock() function shall fail if:
EBUSY The read-write lock could not be acquired for writing because it was already locked
for reading or writing.
The pthread_rwlock_trywrlock() and pthread_rwlock_wrlock() functions may fail if:
EINVAL The value specified by rwlock does not refer to an initialized read-write lock
The pthread_rwlock_wrlock() function may fail if:
The current thread already owns the read-write lock for writing or reading.
These functions shall not return an error code of [EINTR].
The following sections are informative.
Applications using these functions may be subject to priority inversion, as discussed in
the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
pthread_rwlock_destroy() , pthread_rwlock_rdlock() , pthread_rwlock_timedrdlock() ,
pthread_rwlock_timedwrlock() , pthread_rwlock_tryrdlock() , pthread_rwlock_unlock() , the
Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 PTHREAD_RWLOCK_TRYWRLOCK(P)