pthread_rwlock_trywrlock man page on OSF1

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pthread_rwlock_trywrlock(3)			   pthread_rwlock_trywrlock(3)

NAME
       pthread_rwlock_trywrlock	 -  Attempts  to acquire a read-write lock for
       write access without waiting

SYNOPSIS
       #include <pthread.h>

       int pthread_rwlock_trywrlock(
	       pthread_rwlock_t *rwlock );

LIBRARY
       DECthreads POSIX 1003.1c Library (libpthread.so)

PARAMETERS
       Address of the read-write lock object to acquire for write access.

DESCRIPTION
       This routine attempts to acquire	 the  read-write  lock	referenced  by
       rwlock  for  write  access.  If	any thread already holds that lock for
       write access or read access, this routine fails and returns [EBUSY] and
       the calling thread does not wait for the lock to become available.

       Results	are  undefined if the calling thread holds the read-write lock
       (whether for read or write access) at the time this routine is called.

       If the read-write lock object referenced by rwlock is not  initialized,
       the results of calling this routine are undefined.

       Real-time  applications	can  encounter	priority  inversion when using
       read-write locks.  The  problem	occurs	when  a	 high-priority	thread
       acquires	 a  read-write	lock  that  is	about to be unlocked (that is,
       posted) by a low-priority thread, but the low-priority thread  is  pre‐
       empted  by  a  medium-priority  thread. This scenario leads to priority
       inversion in that a high-priority thread is blocked  by	lower-priority
       threads	for  an	 unlimited period of time. During system design, real-
       time programmers must take into account	the  possibility  of  priority
       inversion  and  can deal with it in a number of ways, such as by having
       critical sections that are guarded by read-write	 locks	execute	 at  a
       high  priority, so that a thread cannot be preempted while executing in
       its critical section.

RETURN VALUES
       If an error condition occurs, this routine  returns  an	integer	 value
       indicating  the	type  of error. Possible return values are as follows:
       Successful completion.  The read-write lock could not be	 acquired  for
       write access because it was already locked for write access or for read
       access.	The value specified by rwlock does not refer to an initialized
       read-write lock object.	The current thread already owns the read-write
       lock for write or read access.

ERRORS
       None

SEE ALSO
       Functions:     pthread_rwlock_init(3),	   pthread_rwlockattr_init(3),
       pthread_rwlock_rdlock(3),		     pthread_rwlock_wrlock(3),
       pthread_rwlock_unlock(3)

       Manuals: Guide to DECthreads and Programmer's Guide

						   pthread_rwlock_trywrlock(3)
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