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_timedrdlock() function shall apply a read lock to
the read-write lock referenced by rwlock as in the
pthread_rwlock_rdlock() function. However, if the lock cannot be
acquired without waiting for other threads to unlock the lock, this
wait shall be terminated when the specified timeout expires. The
timeout shall expire when the absolute time specified by abstime
passes, as measured by the clock on which timeouts are based (that
is, when the value of that clock equals or exceeds abstime), or if
the absolute time specified by abstime has already been passed at the
time of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The
resolution of the timeout shall be the resolution of the
CLOCK_REALTIME clock. The timespec data type is defined in the
<time.h> header. Under no circumstances shall the function fail with
a timeout if the lock can be acquired immediately. The validity of
the abstime parameter need not be checked if the lock can be
If a signal that causes a signal handler to be executed is delivered
to a thread blocked on a read-write lock via a call to
pthread_rwlock_timedrdlock(), upon return from the signal handler the
thread shall resume waiting for the lock as if it was not
The calling thread may deadlock if at the time the call is made it
holds a write lock on rwlock. The results are undefined if this
function is called with an uninitialized read-write lock.
The pthread_rwlock_timedrdlock() function shall return zero if the
lock for reading on the read-write lock object referenced by rwlock
is acquired. Otherwise, an error number shall be returned to indicate
The pthread_rwlock_timedrdlock() function shall fail if:
The lock could not be acquired before the specified timeout
The pthread_rwlock_timedrdlock() function may fail if:
EAGAIN The read lock could not be acquired because the maximum number
of read locks for lock would be exceeded.
A deadlock condition was detected or the calling thread
already holds a write lock on rwlock.
EINVAL The abstime nanosecond value is less than zero or greater than
or equal to 1000 million.
This function 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_timedrdlock() does not refer to an
initialized read-write lock object, it is recommended that the
function should fail and report an [EINVAL] error.
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_TIMEDRDLOCK(3P)