_spin_init(3synch)                                _spin_init(3synch)


       NAME
             _spin_init - initialize a spin lock

       SYNOPSIS
             cc [options] -Kthread file
             #include <synch.h>
             int _spin_init(spin_t *lock, void *arg);

          Parameters
             lock   pointer to spin lock to be initialized

             arg    NULL (reserved for future use)

       DESCRIPTION
             _spin_init initializes the spin lock pointed to by lock to the
             unlocked state.  Once initialized, the spin lock can be used
             any number of times without being re-initialized.

          lock Parameter
             lock points to the spin lock to be initialized.

          arg Parameter
             arg should be set to NULL.  It is not currently used, but is
             reserved for future use.

          Static Spin Lock Initialization
             In this implementation, a spin lock can be initialized
             statically if its storage is zero-filled.  In this case, the
             spin lock is of type USYNC_THREAD, and _spin_init need not be
             called.

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

          Errors
             If one of the following conditions is detected, _spin_init
             returns the corresponding value:

             EINVAL   Invalid argument specified.

       USAGE
          Warnings
             Spin locks should not be used on a uniprocessor.  In the best
             case, a spin lock on a uniprocessor will waste resources,
             slowing down the owner of the lock; in the worst case, it will


                           Copyright 1994 Novell, Inc.               Page 1

      _spin_init(3synch)                                _spin_init(3synch)


            deadlock the processor.

            _spin_init does not examine the lock argument before
            initializing it.  If _spin_init is called more than once for
            the same spin lock, it will overwrite its state.  It is the
            user's responsibility to ensure that _spin_init is only called
            once for each spin lock.

            Operations on locks initialized with _spin_init are not
            recursive-a thread can deadlock if it attempts to relock a
            spin lock that it already has locked.

      REFERENCES
            _spin(3synch), _spin_destroy(3synch), _spin_lock(3synch),
            _spin_trylock(3synch), _spin_unlock(3synch), synch(3synch)

































                          Copyright 1994 Novell, Inc.               Page 2