PTHREAD_RWLOCK_TIMEDRDLOCK(3P)                      POSIX Programmer's Manual                     PTHREAD_RWLOCK_TIMEDRDLOCK(3P)



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

NAME
       pthread_rwlock_timedrdlock - lock a read-write lock for reading

SYNOPSIS
       #include <pthread.h>
       #include <time.h>

       int pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
              const struct timespec *restrict abs_timeout);


DESCRIPTION
       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 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 time-
       out 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 signal 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  unde-
       fined if this function is called with an uninitialized read-write lock.

RETURN VALUE
       The  pthread_rwlock_timedrdlock() function shall return zero if the lock for reading on the read-write lock object refer-
       enced by rwlock is acquired. Otherwise, an error number shall be returned to indicate the error.

ERRORS
       The pthread_rwlock_timedrdlock() function shall fail if:

       ETIMEDOUT
              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.

       EDEADLK
              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 nanosec-
              ond 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.

EXAMPLES
       None.

APPLICATION USAGE
       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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       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, <pthread.h>, <time.h>

COPYRIGHT
       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,  Copy-
       right (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   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                PTHREAD_RWLOCK_TIMEDRDLOCK(3P)