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lock.h revision 1.29 
      1 /*	$NetBSD: lock.h,v 1.29 2007/09/10 11:34:09 skrll Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 1998, 1999, 2006 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Paul Kranenburg and Andrew Doran.
      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 #ifndef _MACHINE_LOCK_H
     40 #define _MACHINE_LOCK_H
     41 
     42 /*
     43  * Machine dependent spin lock operations.
     44  */
     45 
     46 #if __SIMPLELOCK_UNLOCKED != 0
     47 #error __SIMPLELOCK_UNLOCKED must be 0 for this implementation
     48 #endif
     49 
     50 /* XXX So we can expose this to userland. */
     51 #ifdef __lint__
     52 #define __ldstub(__addr)	(__addr)
     53 #else /* !__lint__ */
     54 static __inline int __ldstub(__cpu_simple_lock_t *addr);
     55 static __inline int __ldstub(__cpu_simple_lock_t *addr)
     56 {
     57 	int v;
     58 
     59 	__asm volatile("ldstub [%1],%0"
     60 	    : "=&r" (v)
     61 	    : "r" (addr)
     62 	    : "memory");
     63 
     64 	return v;
     65 }
     66 #endif /* __lint__ */
     67 
     68 static __inline void __cpu_simple_lock_init(__cpu_simple_lock_t *)
     69 	__attribute__((__unused__));
     70 static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *)
     71 	__attribute__((__unused__));
     72 static __inline void __cpu_simple_unlock(__cpu_simple_lock_t *)
     73 	__attribute__((__unused__));
     74 #ifndef __CPU_SIMPLE_LOCK_NOINLINE
     75 static __inline void __cpu_simple_lock(__cpu_simple_lock_t *)
     76 	__attribute__((__unused__));
     77 #else
     78 extern void __cpu_simple_lock(__cpu_simple_lock_t *);
     79 #endif
     80 
     81 static __inline int
     82 __SIMPLELOCK_LOCKED_P(__cpu_simple_lock_t *__ptr)
     83 {
     84 	return *__ptr == __SIMPLELOCK_LOCKED;
     85 }
     86 
     87 static __inline int
     88 __SIMPLELOCK_UNLOCKED_P(__cpu_simple_lock_t *__ptr)
     89 {
     90 	return *__ptr == __SIMPLELOCK_UNLOCKED;
     91 }
     92 
     93 static __inline void
     94 __cpu_simple_lock_clear(__cpu_simple_lock_t *__ptr)
     95 {
     96 	*__ptr = __SIMPLELOCK_UNLOCKED;
     97 }
     98 
     99 static __inline void
    100 __cpu_simple_lock_set(__cpu_simple_lock_t *__ptr)
    101 {
    102 	*__ptr = __SIMPLELOCK_LOCKED;
    103 }
    104 
    105 static __inline void
    106 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
    107 {
    108 
    109 	*alp = __SIMPLELOCK_UNLOCKED;
    110 }
    111 
    112 #ifndef __CPU_SIMPLE_LOCK_NOINLINE
    113 static __inline void
    114 __cpu_simple_lock(__cpu_simple_lock_t *alp)
    115 {
    116 
    117 	/*
    118 	 * If someone else holds the lock use simple reads until it
    119 	 * is released, then retry the atomic operation. This reduces
    120 	 * memory bus contention because the cache-coherency logic
    121 	 * does not have to broadcast invalidates on the lock while
    122 	 * we spin on it.
    123 	 */
    124 	while (__ldstub(alp) != __SIMPLELOCK_UNLOCKED) {
    125 		while (*alp != __SIMPLELOCK_UNLOCKED)
    126 			/* spin */ ;
    127 	}
    128 }
    129 #endif /* __CPU_SIMPLE_LOCK_NOINLINE */
    130 
    131 static __inline int
    132 __cpu_simple_lock_try(__cpu_simple_lock_t *alp)
    133 {
    134 
    135 	return (__ldstub(alp) == __SIMPLELOCK_UNLOCKED);
    136 }
    137 
    138 static __inline void
    139 __cpu_simple_unlock(__cpu_simple_lock_t *alp)
    140 {
    141 
    142 	/*
    143 	 * Insert compiler barrier to prevent instruction re-ordering
    144 	 * around the lock release.
    145 	 */
    146 	__insn_barrier();
    147 	*alp = __SIMPLELOCK_UNLOCKED;
    148 }
    149 
    150 #if defined(__sparc_v9__)
    151 static __inline void
    152 mb_read(void)
    153 {
    154 	__asm __volatile("membar #LoadLoad" : : : "memory");
    155 }
    156 
    157 static __inline void
    158 mb_write(void)
    159 {
    160 	__asm __volatile("" : : : "memory");
    161 }
    162 
    163 static __inline void
    164 mb_memory(void)
    165 {
    166 	__asm __volatile("membar #MemIssue" : : : "memory");
    167 }
    168 #else	/* __sparc_v9__ */
    169 static __inline void
    170 mb_read(void)
    171 {
    172 	static volatile int junk;
    173 	__asm volatile("st %%g0,[%0]"
    174 	    :
    175 	    : "r" (&junk)
    176 	    : "memory");
    177 }
    178 
    179 static __inline void
    180 mb_write(void)
    181 {
    182 	__insn_barrier();
    183 }
    184 
    185 static __inline void
    186 mb_memory(void)
    187 {
    188 	mb_read();
    189 }
    190 #endif	/* __sparc_v9__ */
    191 
    192 #endif /* _MACHINE_LOCK_H */
    193