2 * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
4 * copyright Douglas Santry 1996
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the above copyright is retained
10 * THIS SOFTWARE IS PROVIDED BY Douglas Santry AND CONTRIBUTORS ``AS IS'' AND
11 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
12 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
13 * ARE DISCLAIMED. IN NO EVENT SHALL Douglas Santry OR CONTRIBUTORS BE LIABLE
14 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
15 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
16 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
17 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
18 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
19 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
22 * $FreeBSD: src/lib/libc_r/arch/alpha/_atomic_lock.S,v 1.3 1999/08/28 00:03:00 peter Exp $
23 * $DragonFly: src/lib/libc_r/arch/alpha/Attic/_atomic_lock.S,v 1.2 2003/06/17 04:26:47 dillon Exp $
30 * Atomicly lock a location with an identifier provided the location
31 * is not currently locked.
33 * long _atomic_lock(long *);
34 * v0 will contain the return value (zero if lock obtained).
39 0: ldq_l v0, 0(a0) /* read existing lock value */
40 mov 1, t0 /* locked value to store */
41 stq_c t0, 0(a0) /* attempt to store, status in t0 */
42 beq t0, 1f /* branch foward to optimise prediction */
43 mb /* sync with other processors */
44 RET /* return with v0==0 if lock obtained */
45 1: br 0b /* loop to try again */