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