rw_tryrdlock(3synch)                            rw_tryrdlock(3synch)


       NAME
             rw_tryrdlock - conditionally acquire a reader-writer lock in
             read mode

       SYNOPSIS
             cc [options] -Kthread file
             #include <synch.h>
             int rw_tryrdlock(rwlock_t *lock);

          Parameters
             lock  pointer to the lock to be acquired

       DESCRIPTION
             rw_tryrdlock attempts once to acquire the reader-writer lock
             pointed to by lock in read mode; it does not block the caller
             if the lock is unavailable.

             A reader-writer lock can be held by any number of readers at
             one time, but only one writer at a time can hold the lock.

             If the lock is free, rw_trywrlock increments the reader count
             and the caller proceeds.

             If the lock is currently held by a writer, or there are
             writers waiting, rw_tryrdlock immediately returns EBUSY to the
             caller, without acquiring the lock.

             lock must previously have been initialized (see rwlock_init).

          Return Values
             rw_tryrdlock returns zero for success and an error number for
             failure, as described below.

          Errors
             If any of the following conditions occurs, rw_tryrdlock fails
             and returns the corresponding value:

             EBUSY    The reader-writer lock pointed to by lock cannot be
                      acquired.

             If any of the following conditions is detected, rw_tryrdlock
             returns the corresponding value:

             EINVAL   Invalid argument specified.




                           Copyright 1994 Novell, Inc.               Page 1

      rw_tryrdlock(3synch)                            rw_tryrdlock(3synch)


      USAGE
            rw_tryrdlock is used when the caller does not want to block if
            the lock is unavailable.

            For consistency, locks acquired with rw_tryrdlock should be
            released with rw_unlock.

      REFERENCES
            rwlock(3synch), rwlock_destroy(3synch), rwlock_init(3synch),
            rw_rdlock(3synch), rw_trywrlock(3synch), rw_unlock(3synch),
            rw_wrlock(3synch), synch(3synch)





































                          Copyright 1994 Novell, Inc.               Page 2