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.
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
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
Implementations may favor writers over readers to avoid writer
Results are undefined if any of these functions are called with an
uninitialized read-write lock.
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
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
If successful, the pthread_rwlock_wrlock() function shall return
zero; otherwise, an error number shall be returned to indicate the
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_wrlock() function may fail if:
A deadlock condition was detected or 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.
If an implementation detects that the value specified by the rwlock
argument to pthread_rwlock_trywrlock() or pthread_rwlock_wrlock()
does not refer to an initialized read-write lock object, it is
recommended that the function should fail and report an [EINVAL]
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 PTHREAD_RWLOCK_TRYWRLOCK(3P)