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PTHREAD_RWLOCK_TIMEDRDLOCK(POSIX Programmer's MaPTHREAD_RWLOCK_TIMEDRDLOCK(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.
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 time-
       out  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 time-
       out  shall be based on the system clock as returned by the time() func-
       tion. 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  immedi-
       ately 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 undefined if this func-
       tion 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 referenced 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 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.
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,  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 original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003       PTHREAD_RWLOCK_TIMEDRDLOCK(3P)