1 /* $NetBSD: lock.h,v 1.34 2019/11/29 20:05:19 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2000, 2001 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Machine-dependent spin lock operations. 34 * 35 * NOTE: The SWP insn used here is available only on ARM architecture 36 * version 3 and later (as well as 2a). What we are going to do is 37 * expect that the kernel will trap and emulate the insn. That will 38 * be slow, but give us the atomicity that we need. 39 */ 40 41 #ifndef _ARM_LOCK_H_ 42 #define _ARM_LOCK_H_ 43 44 static __inline int 45 __SIMPLELOCK_LOCKED_P(const __cpu_simple_lock_t *__ptr) 46 { 47 return *__ptr == __SIMPLELOCK_LOCKED; 48 } 49 50 static __inline int 51 __SIMPLELOCK_UNLOCKED_P(const __cpu_simple_lock_t *__ptr) 52 { 53 return *__ptr == __SIMPLELOCK_UNLOCKED; 54 } 55 56 static __inline void 57 __cpu_simple_lock_clear(__cpu_simple_lock_t *__ptr) 58 { 59 *__ptr = __SIMPLELOCK_UNLOCKED; 60 } 61 62 static __inline void 63 __cpu_simple_lock_set(__cpu_simple_lock_t *__ptr) 64 { 65 *__ptr = __SIMPLELOCK_LOCKED; 66 } 67 68 #ifdef _KERNEL 69 /* XXX Formerly included for obsolete mb_* API, maybe no longer needed. */ 70 #include <arm/cpufunc.h> 71 #endif 72 73 #ifdef _ARM_ARCH_6 74 static __inline unsigned int 75 __arm_load_exclusive(__cpu_simple_lock_t *__alp) 76 { 77 unsigned int __rv; 78 if (/*CONSTCOND*/sizeof(*__alp) == 1) { 79 __asm __volatile("ldrexb\t%0,[%1]" : "=r"(__rv) : "r"(__alp)); 80 } else { 81 __asm __volatile("ldrex\t%0,[%1]" : "=r"(__rv) : "r"(__alp)); 82 } 83 return __rv; 84 } 85 86 /* returns 0 on success and 1 on failure */ 87 static __inline unsigned int 88 __arm_store_exclusive(__cpu_simple_lock_t *__alp, unsigned int __val) 89 { 90 unsigned int __rv; 91 if (/*CONSTCOND*/sizeof(*__alp) == 1) { 92 __asm __volatile("strexb\t%0,%1,[%2]" 93 : "=&r"(__rv) : "r"(__val), "r"(__alp) : "cc", "memory"); 94 } else { 95 __asm __volatile("strex\t%0,%1,[%2]" 96 : "=&r"(__rv) : "r"(__val), "r"(__alp) : "cc", "memory"); 97 } 98 return __rv; 99 } 100 #elif defined(_KERNEL) 101 static __inline unsigned char 102 __swp(unsigned char __val, __cpu_simple_lock_t *__ptr) 103 { 104 uint32_t __val32; 105 __asm volatile("swpb %0, %1, [%2]" 106 : "=&r" (__val32) : "r" (__val), "r" (__ptr) : "memory"); 107 return __val32; 108 } 109 #else 110 /* 111 * On MP Cortex, SWP no longer guarantees atomic results. Thus we pad 112 * out SWP so that when the cpu generates an undefined exception we can replace 113 * the SWP/MOV instructions with the right LDREX/STREX instructions. 114 * 115 * This is why we force the SWP into the template needed for LDREX/STREX 116 * including the extra instructions and extra register for testing the result. 117 */ 118 static __inline int 119 __swp(int __val, __cpu_simple_lock_t *__ptr) 120 { 121 int __tmp, __rv; 122 __asm volatile( 123 #if 1 124 "1:\t" "swp %[__rv], %[__val], [%[__ptr]]" 125 "\n\t" "b 2f" 126 #else 127 "1:\t" "ldrex %[__rv],[%[__ptr]]" 128 "\n\t" "strex %[__tmp],%[__val],[%[__ptr]]" 129 #endif 130 "\n\t" "cmp %[__tmp],#0" 131 "\n\t" "bne 1b" 132 "\n" "2:" 133 : [__rv] "=&r" (__rv), [__tmp] "=&r" (__tmp) 134 : [__val] "r" (__val), [__ptr] "r" (__ptr) : "cc", "memory"); 135 return __rv; 136 } 137 #endif /* !_ARM_ARCH_6 */ 138 139 static __inline void 140 __arm_membar_producer(void) 141 { 142 #ifdef _ARM_ARCH_7 143 __asm __volatile("dsb" ::: "memory"); 144 #elif defined(_ARM_ARCH_6) 145 __asm __volatile("mcr\tp15,0,%0,c7,c10,4" :: "r"(0) : "memory"); 146 #endif 147 } 148 149 static __inline void 150 __arm_membar_consumer(void) 151 { 152 #ifdef _ARM_ARCH_7 153 __asm __volatile("dmb" ::: "memory"); 154 #elif defined(_ARM_ARCH_6) 155 __asm __volatile("mcr\tp15,0,%0,c7,c10,5" :: "r"(0) : "memory"); 156 #endif 157 } 158 159 static __inline void __unused 160 __cpu_simple_lock_init(__cpu_simple_lock_t *__alp) 161 { 162 163 *__alp = __SIMPLELOCK_UNLOCKED; 164 __arm_membar_producer(); 165 } 166 167 #if !defined(__thumb__) || defined(_ARM_ARCH_T2) 168 static __inline void __unused 169 __cpu_simple_lock(__cpu_simple_lock_t *__alp) 170 { 171 #ifdef _ARM_ARCH_6 172 __arm_membar_consumer(); 173 do { 174 /* spin */ 175 } while (__arm_load_exclusive(__alp) != __SIMPLELOCK_UNLOCKED 176 || __arm_store_exclusive(__alp, __SIMPLELOCK_LOCKED)); 177 __arm_membar_producer(); 178 #else 179 while (__swp(__SIMPLELOCK_LOCKED, __alp) != __SIMPLELOCK_UNLOCKED) 180 continue; 181 #endif 182 } 183 #else 184 void __cpu_simple_lock(__cpu_simple_lock_t *); 185 #endif 186 187 #if !defined(__thumb__) || defined(_ARM_ARCH_T2) 188 static __inline int __unused 189 __cpu_simple_lock_try(__cpu_simple_lock_t *__alp) 190 { 191 #ifdef _ARM_ARCH_6 192 __arm_membar_consumer(); 193 do { 194 if (__arm_load_exclusive(__alp) != __SIMPLELOCK_UNLOCKED) { 195 return 0; 196 } 197 } while (__arm_store_exclusive(__alp, __SIMPLELOCK_LOCKED)); 198 __arm_membar_producer(); 199 return 1; 200 #else 201 return (__swp(__SIMPLELOCK_LOCKED, __alp) == __SIMPLELOCK_UNLOCKED); 202 #endif 203 } 204 #else 205 int __cpu_simple_lock_try(__cpu_simple_lock_t *); 206 #endif 207 208 static __inline void __unused 209 __cpu_simple_unlock(__cpu_simple_lock_t *__alp) 210 { 211 212 #ifdef _ARM_ARCH_8 213 if (sizeof(*__alp) == 1) { 214 __asm __volatile("stlb\t%0, [%1]" 215 :: "r"(__SIMPLELOCK_UNLOCKED), "r"(__alp) : "memory"); 216 } else { 217 __asm __volatile("stl\t%0, [%1]" 218 :: "r"(__SIMPLELOCK_UNLOCKED), "r"(__alp) : "memory"); 219 } 220 #else 221 __arm_membar_consumer(); 222 *__alp = __SIMPLELOCK_UNLOCKED; 223 __arm_membar_producer(); 224 #endif 225 } 226 227 #endif /* _ARM_LOCK_H_ */ 228