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atomic_init_testset.c revision 1.4 
      1 /*	$NetBSD: atomic_init_testset.c,v 1.4 2008/04/28 20:22:53 martin 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  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * libc glue for atomic operations where the hardware does not provide
     31  * compare-and-swap.  It's assumed that this will only be used on 32-bit
     32  * platforms.
     33  *
     34  * This should be compiled with '-fno-reorder-blocks -fomit-frame-pointer'
     35  * if using gcc.
     36  */
     37 
     38 #include <sys/cdefs.h>
     39 __RCSID("$NetBSD: atomic_init_testset.c,v 1.4 2008/04/28 20:22:53 martin Exp $");
     40 
     41 #include "atomic_op_namespace.h"
     42 
     43 #include <sys/types.h>
     44 #include <sys/atomic.h>
     45 #include <sys/lock.h>
     46 #include <sys/ras.h>
     47 #include <sys/sysctl.h>
     48 
     49 #include <string.h>
     50 
     51 #define	I2	__SIMPLELOCK_UNLOCKED, __SIMPLELOCK_UNLOCKED,
     52 #define	I16	I2 I2 I2 I2 I2 I2 I2 I2
     53 #define	I128	I16 I16 I16 I16 I16 I16 I16 I16
     54 
     55 static __cpu_simple_lock_t atomic_locks[128] = { I128 };
     56 static uint32_t (*_atomic_cas_fn)(volatile uint32_t *, uint32_t, uint32_t);
     57 
     58 void	__libc_atomic_init(void) __attribute__ ((visibility("hidden")));
     59 
     60 RAS_DECL(_atomic_cas);
     61 
     62 static uint32_t
     63 _atomic_cas_up(volatile uint32_t *ptr, uint32_t old, uint32_t new)
     64 {
     65 	uint32_t ret;
     66 
     67 	RAS_START(_atomic_cas);
     68 	ret = *ptr;
     69 	if (__predict_false(ret != old)) {
     70 		return ret;
     71 	}
     72 	*ptr = new;
     73 	RAS_END(_atomic_cas);
     74 
     75 	return ret;
     76 }
     77 
     78 static uint32_t
     79 _atomic_cas_mp(volatile uint32_t *ptr, uint32_t old, uint32_t new)
     80 {
     81 	__cpu_simple_lock_t *lock;
     82 	uint32_t ret;
     83 
     84 	lock = &atomic_locks[((uint32_t)ptr >> 3) & 127];
     85 	__cpu_simple_lock(lock);
     86 	ret = *ptr;
     87 	if (__predict_true(ret == old)) {
     88 		*ptr = new;
     89 	}
     90 	__cpu_simple_unlock(lock);
     91 
     92 	return ret;
     93 }
     94 
     95 uint32_t
     96 _atomic_cas_32(volatile uint32_t *ptr, uint32_t old, uint32_t new)
     97 {
     98 
     99 	return (*_atomic_cas_fn)(ptr, old, new);
    100 }
    101 
    102 void
    103 __libc_atomic_init(void)
    104 {
    105 	int ncpu, mib[2];
    106 	size_t len;
    107 
    108 	_atomic_cas_fn = _atomic_cas_mp;
    109 
    110 	mib[0] = CTL_HW;
    111 	mib[1] = HW_NCPU;
    112 	len = sizeof(ncpu);
    113 	if (sysctl(mib, 2, &ncpu, &len, NULL, 0) == -1)
    114 		return;
    115 	if (ncpu > 1)
    116 		return;
    117 	if (rasctl(RAS_ADDR(_atomic_cas), RAS_SIZE(_atomic_cas),
    118 	    RAS_INSTALL) == 0) {
    119 		_atomic_cas_fn = _atomic_cas_up;
    120 		return;
    121 	}
    122 }
    123 
    124 #undef atomic_cas_32
    125 #undef atomic_cas_uint
    126 #undef atomic_cas_ulong
    127 #undef atomic_cas_ptr
    128 
    129 atomic_op_alias(atomic_cas_32,_atomic_cas_32)
    130 atomic_op_alias(atomic_cas_uint,_atomic_cas_32)
    131 __strong_alias(_atomic_cas_uint,_atomic_cas_32)
    132 atomic_op_alias(atomic_cas_ulong,_atomic_cas_32)
    133 __strong_alias(_atomic_cas_ulong,_atomic_cas_32)
    134 atomic_op_alias(atomic_cas_ptr,_atomic_cas_32)
    135 __strong_alias(_atomic_cas_ptr,_atomic_cas_32)
    136 
    137 atomic_op_alias(atomic_cas_32_ni,_atomic_cas_32)
    138 __strong_alias(_atomic_cas_32_ni,_atomic_cas_32)
    139 atomic_op_alias(atomic_cas_uint_ni,_atomic_cas_32)
    140 __strong_alias(_atomic_cas_uint_ni,_atomic_cas_32)
    141 atomic_op_alias(atomic_cas_ulong_ni,_atomic_cas_32)
    142 __strong_alias(_atomic_cas_ulong_ni,_atomic_cas_32)
    143 atomic_op_alias(atomic_cas_ptr_ni,_atomic_cas_32)
    144 __strong_alias(_atomic_cas_ptr_ni,_atomic_cas_32)
    145