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atomic_cas.S revision 1.4 
      1 /*	$NetBSD: atomic_cas.S,v 1.4 2007/12/08 22:53:33 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2007 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Andrew Doran and Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the NetBSD
     21  *	Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include "atomic_op_asm.h"
     40 
     41 #if defined(_KERNEL)
     42 
     43 #include <machine/psl.h>
     44 
     45 #include "opt_multiprocessor.h"
     46 
     47 #define	DISABLE_INTERRUPTS						 \
     48 	rd	%psr, %o4			/* disable interrupts */;\
     49 	or	%o4, PSR_PIL, %o5					;\
     50 	wr	%o5, 0, %psr						;\
     51 	nop								;\
     52 	nop								;\
     53 	nop
     54 
     55 #define	RESTORE_INTERRUPTS						 \
     56 	wr	%o4, 0, %psr			/* enable interrupts */	;\
     57 	nop								;\
     58 	nop								;\
     59 	nop
     60 
     61 #else	/* _KERNEL */
     62 
     63 #define	MULTIPROCESSOR	1
     64 #define	DISABLE_INTERRUPTS		/* nothing */
     65 #define	RESTORE_INTERRUPTS		/* nothing */
     66 
     67 #endif	/* _KERNEL */
     68 
     69 #if defined(MULTIPROCESSOR)
     70 	.section .bss
     71 	.align	1024
     72 OTYPE(_C_LABEL(_atomic_cas_locktab))
     73 _C_LABEL(_atomic_cas_locktab):
     74 	.space	1024
     75 
     76 #define	ACQUIRE_INTERLOCK						 \
     77 	DISABLE_INTERRUPTS						;\
     78 	srl	%o0, 3, %o5			/* get lock address */	;\
     79 	and	%o5, 1023, %o5						;\
     80 	sethi	%hi(_C_LABEL(_atomic_cas_locktab)), %o3			;\
     81 	add	%o5, %o3, %o5						;\
     82 									;\
     83 	/* %o5 has interlock address */					;\
     84 									;\
     85 1:	ldstub	[%o5], %o3			/* acquire lock */	;\
     86 	tst	%o3							;\
     87 	bz,a	2f							;\
     88 	 nop								;\
     89 	nop								;\
     90 	nop								;\
     91 	b,a	1b				/* spin	*/		;\
     92 	 nop								;\
     93 	/* We now hold the interlock */					;\
     94 2:
     95 
     96 #define	RELEASE_INTERLOCK						 \
     97 	stb	%g0, [%o5]			/* release interlock */	;\
     98 	RESTORE_INTERRUPTS
     99 
    100 #else /* ! MULTIPROCESSOR */
    101 
    102 #define	ACQUIRE_INTERLOCK	DISABLE_INTERRUPTS
    103 
    104 #define	RELEASE_INTERLOCK	RESTORE_INTERRUPTS
    105 
    106 #endif /* MULTIPROCESSOR */
    107 
    108 	.text
    109 
    110 /*
    111  * The v7 and v8 SPARC doesn't have compare-and-swap, so we block interrupts
    112  * and use an interlock.
    113  *
    114  * XXX On single CPU systems, this should use a restartable sequence:
    115  * XXX there we don't need the overhead of interlocking.
    116  *
    117  * XXX NOTE!  The interlock trick only works if EVERYTHING writes to
    118  * XXX the memory cell through this code path!
    119  */
    120 ENTRY_NOPROFILE(_atomic_cas_32)
    121 	ACQUIRE_INTERLOCK
    122 	! %o4 has saved PSR value
    123 	! %o5 has interlock address
    124 
    125 	ld	[%o0], %o3			! get old value
    126 	cmp	%o1, %o3			! old == new?
    127 	beq,a	3f				! yes, do the store
    128 	 st	%o2, [%o0]			! (in the delay slot)
    129 
    130 3:	RELEASE_INTERLOCK
    131 
    132 	retl
    133 	 mov	%o3, %o0			! return old value
    134 
    135 ATOMIC_OP_ALIAS(atomic_cas_32,_atomic_cas_32)
    136 ATOMIC_OP_ALIAS(atomic_cas_uint,_atomic_cas_32)
    137 STRONG_ALIAS(_atomic_cas_uint,_atomic_cas_32)
    138 ATOMIC_OP_ALIAS(atomic_cas_ulong,_atomic_cas_32)
    139 STRONG_ALIAS(_atomic_cas_ulong,_atomic_cas_32)
    140 ATOMIC_OP_ALIAS(atomic_cas_ptr,_atomic_cas_32)
    141 STRONG_ALIAS(_atomic_cas_ptr,_atomic_cas_32)
    142