PTHREAD_RWLOCK_TRYWRLOCK(3)POSIX Programmer's ManualPTHREAD_RWLOCK_TRYWRLOCK(3)



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

NAME
       pthread_rwlock_trywrlock, pthread_rwlock_wrlock -- lock a read-write
       lock object for writing

SYNOPSIS
       #include <pthread.h>

       int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
       int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

DESCRIPTION
       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 referenced by rwlock.  The calling thread shall acquire
       the write lock if no thread (reader or writer) holds the read-write
       lock rwlock.  Otherwise, if another thread holds the read-write lock
       rwlock, the calling thread shall block until it can acquire the lock.
       If a deadlock condition occurs or the calling thread already owns the
       read-write lock for writing or reading, the call shall either deadlock
       or return [EDEADLK].

       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.

RETURN VALUE
       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.

ERRORS
       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:

       EDEADLK
              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.

EXAMPLES
       None.

APPLICATION USAGE
       Applications using these functions may be subject to priority
       inversion, as discussed in the Base Definitions volume of POSIX.1-2017,
       Section 3.291, Priority Inversion.

RATIONALE
       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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       pthread__rwlock__destroy(), pthread__rwlock__rdlock(),
       pthread__rwlock__timedrdlock(), pthread__rwlock__timedwrlock(),
       pthread__rwlock__unlock()

       The Base Definitions volume of POSIX.1-2017, Section 3.291, Priority
       Inversion, Section 4.12, Memory Synchronization, <pthread.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017          PTHREAD_RWLOCK_TRYWRLOCK(3)
