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Linux 2.6 - man page for pthread_rwlock_timedrdlock (linux section 3posix)

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

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 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-
       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003		    PTHREAD_RWLOCK_TIMEDRDLOCK(P)


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