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/*
* Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
* copyright Douglas Santry 1996
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the above copyright is retained
* in the source form.
*
* THIS SOFTWARE IS PROVIDED BY Douglas Santry AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL Douglas Santry OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: _atomic_lock.S,v 1.1 1998/06/09 08:21:55 jb Exp $
*
*/
#include "SYS.h"
/*
* Atomicly lock a location with an identifier provided the location
* is not currently locked.
*
* long _atomic_lock(long *);
* v0 will contain the return value (zero if lock obtained).
*/
LEAF(_atomic_lock,0)
LDGP(pv)
0: ldq_l v0, 0(a0) /* read existing lock value */
mov 1, t0 /* locked value to store */
stq_c t0, 0(a0) /* attempt to store, status in t0 */
beq t0, 1f /* branch foward to optimise prediction */
mb /* sync with other processors */
RET /* return with v0==0 if lock obtained */
1: br 0b /* loop to try again */
END(_atomic_lock)
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