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 abstime);

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 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  circum-
       stances	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 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 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
	      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.

EXAMPLES
       None.

APPLICATION USAGE
       Applications  using this function may be subject to priority inversion,
       as discussed in the Base Definitions volume  of	POSIX.1-2008,  Section
       3.287, Priority Inversion.

RATIONALE
       If  an  implementation  detects	that the value specified by the rwlock
       argument to pthread_rwlock_timedrdlock() does not refer to an  initial-
       ized read-write lock object, it is recommended that the function should
       fail and report an [EINVAL] error.

FUTURE DIRECTIONS
       None.

SEE ALSO
       pthread_rwlock_destroy(), pthread_rwlock_rdlock(),
       pthread_rwlock_timedwrlock(), pthread_rwlock_trywrlock(),
       pthread_rwlock_unlock()

       The Base Definitions volume of POSIX.1-2008,  Section  3.287,  Priority
       Inversion, Section 4.11, Memory Synchronization, <pthread.h>, <time.h>

COPYRIGHT
       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 Electri-
       cal  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  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group		     2013	PTHREAD_RWLOCK_TIMEDRDLOCK(3P)