PTHREAD_RWLOCK_TRYWRLOCK(3PPOSIX Programmer's ManuPTHREAD_RWLOCK_TRYWRLOCK(3P)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_trywrlock, pthread_rwlock_wrlock — lock a read-write
lock object for writing
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 func‐
tion 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 starva‐
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 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
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_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.
Applications using these functions may be subject to priority inver‐
sion, as discussed in the Base Definitions volume of POSIX.1‐2008, Sec‐
tion 3.287, Priority Inversion.
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] error.
SEE ALSOpthread_rwlock_destroy(), pthread_rwlock_rdlock(), pthread_rwlock_time‐
drdlock(), pthread_rwlock_timedwrlock(), pthread_rwlock_unlock()
The Base Definitions volume of POSIX.1‐2008, Section 3.287, Priority
Inversion, Section 4.11, Memory Synchronization, <pthread.h>
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 Electri‐
cal 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 .
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