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atomic_init_testset.c revision 1.1 
      1 /*	$NetBSD: atomic_init_testset.c,v 1.1 2008/02/09 13:30:54 ad Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2008 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *        This product includes software developed by the NetBSD
     18  *        Foundation, Inc. and its contributors.
     19  * 4. Neither the name of The NetBSD Foundation nor the names of its
     20  *    contributors may be used to endorse or promote products derived
     21  *    from this software without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     24  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     25  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     26  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     27  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     28  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     29  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     30  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     31  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     32  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     33  * POSSIBILITY OF SUCH DAMAGE.
     34  */
     35 
     36 /*
     37  * libc glue for atomic operations where the hardware does not provide
     38  * compare-and-swap.  It's assumed that this will only be used on 32-bit
     39  * platforms.
     40  *
     41  * This should be compiled with '-fno-reorder-blocks -fomit-frame-pointer'
     42  * if using gcc.
     43  */
     44 
     45 #include <sys/cdefs.h>
     46 __RCSID("$NetBSD: atomic_init_testset.c,v 1.1 2008/02/09 13:30:54 ad Exp $");
     47 
     48 #include "atomic_op_namespace.h"
     49 
     50 #include <sys/types.h>
     51 #include <sys/atomic.h>
     52 #include <sys/lock.h>
     53 #include <sys/ras.h>
     54 #include <sys/sysctl.h>
     55 
     56 #include <string.h>
     57 
     58 #define	I2	__SIMPLELOCK_UNLOCKED, __SIMPLELOCK_UNLOCKED,
     59 #define	I16	I2 I2 I2 I2 I2 I2 I2 I2
     60 #define	I128	I16 I16 I16 I16 I16 I16 I16 I16
     61 
     62 static __cpu_simple_lock_t atomic_locks[128] = { I128 };
     63 static uint32_t (*_atomic_cas_fn)(volatile uint32_t *, uint32_t, uint32_t);
     64 
     65 void	_libc_atomic_init(void) __attribute__ ((visibility("hidden")));
     66 
     67 RAS_DECL(_atomic_cas);
     68 
     69 static uint32_t
     70 _atomic_cas_up(volatile uint32_t *ptr, uint32_t old, uint32_t new)
     71 {
     72 	uint32_t ret;
     73 
     74 	RAS_START(_atomic_cas);
     75 	ret = *ptr;
     76 	if (ret != old) {
     77 		return ret;
     78 	}
     79 	*ptr = new;
     80 	RAS_END(_atomic_cas);
     81 
     82 	return ret;
     83 }
     84 
     85 static uint32_t
     86 _atomic_cas_mp(volatile uint32_t *ptr, uint32_t old, uint32_t new)
     87 {
     88 	__cpu_simple_lock_t *lock;
     89 	uint32_t ret;
     90 
     91 	lock = &atomic_locks[(uint32_t)ptr >> 3];
     92 	__cpu_simple_lock(lock);
     93 	ret = *ptr;
     94 	if (__predict_true(ret == old)) {
     95 		*ptr = new;
     96 	}
     97 	__cpu_simple_unlock(lock);
     98 
     99 	return ret;
    100 }
    101 
    102 uint32_t
    103 _atomic_cas_32(volatile uint32_t *ptr, uint32_t old, uint32_t new)
    104 {
    105 
    106 	return (*_atomic_cas_fn)(ptr, old, new);
    107 }
    108 
    109 void
    110 _libc_atomic_init(void)
    111 {
    112 	int ncpu, mib[2];
    113 	size_t len;
    114 
    115 	_atomic_cas_fn = _atomic_cas_mp;
    116 
    117 	mib[0] = CTL_HW;
    118 	mib[1] = HW_NCPU;
    119 	len = sizeof(ncpu);
    120 	if (sysctl(mib, 2, &ncpu, &len, NULL, 0) == -1)
    121 		return;
    122 	if (ncpu > 1)
    123 		return;
    124 	if (rasctl(RAS_ADDR(_atomic_cas), RAS_SIZE(_atomic_cas),
    125 	    RAS_INSTALL) == 0) {
    126 		_atomic_cas_fn = _atomic_cas_up;
    127 		return;
    128 	}
    129 }
    130 
    131 #undef atomic_cas_32
    132 atomic_op_alias(atomic_cas_32,_atomic_cas_32)
    133 #undef atomic_cas_uint
    134 atomic_op_alias(atomic_cas_uint,_atomic_cas_32)
    135 __strong_alias(_atomic_cas_uint,_atomic_cas_32)
    136 #undef atomic_cas_ulong
    137 atomic_op_alias(atomic_cas_ulong,_atomic_cas_32)
    138 __strong_alias(_atomic_cas_ulong,_atomic_cas_32)
    139 #undef atomic_cas_ptr
    140 atomic_op_alias(atomic_cas_ptr,_atomic_cas_32)
    141 __strong_alias(_atomic_cas_ptr,_atomic_cas_32)
    142