PTHREAD_RWLOCK_TIMEDRDLOCK(P) POSIX Programmer's Manual PTHREAD_RWLOCK_TIMEDRDLOCK(P)
pthread_rwlock_timedrdlock - lock a read-write lock for reading
int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
const struct timespec *restrict abs_timeout);
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 can-
not 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 abs_timeout passes, as measured by the clock on which timeouts are based
(that is, when the value of that clock equals or exceeds abs_timeout), or if the absolute
time specified by abs_timeout has already been passed at the time of the call.
If the Timers option is supported, the timeout shall be based on the CLOCK_REALTIME clock.
If the Timers option is not supported, the timeout shall be based on the system clock as
returned by the time() function. The resolution of the timeout shall be the resolution of
the clock on which it is based. 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 abs_timeout parameter need not be checked if the lock can
be immediately acquired.
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 sig-
nal handler the thread shall resume waiting for the lock as if it was not interrupted.
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-
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 error.
The pthread_rwlock_timedrdlock() function shall fail if:
The lock could not be acquired before the specified timeout expired.
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.
The calling thread already holds a write lock on rwlock.
EINVAL The value specified by rwlock does not refer to an initialized read-write lock
object, or the abs_timeout 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.
Applications using this function may be subject to priority inversion, as discussed in the
Base Definitions volume of IEEE Std 1003.1-2001, Section 3.285, Priority Inversion.
The pthread_rwlock_timedrdlock() function is part of the Threads and Timeouts options and
need not be provided on all implementations.
pthread_rwlock_destroy() , pthread_rwlock_rdlock() , pthread_rwlock_timedwrlock() ,
pthread_rwlock_tryrdlock() , pthread_rwlock_trywrlock() , pthread_rwlock_unlock() ,
pthread_rwlock_wrlock() , the Base Definitions volume of IEEE Std 1003.1-2001,
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_TIMEDRDLOCK(P)