1 /* $NetBSD: spinlock.h,v 1.15 2022/10/25 23:33:29 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2013 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Taylor R. Campbell. 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 #ifndef _LINUX_SPINLOCK_H_ 33 #define _LINUX_SPINLOCK_H_ 34 35 #include <sys/cdefs.h> 36 #include <sys/mutex.h> 37 38 #include <machine/limits.h> 39 40 #include <linux/atomic.h> 41 #include <linux/irqflags.h> 42 #include <linux/lockdep.h> 43 #include <linux/preempt.h> 44 45 typedef struct spinlock { 46 kmutex_t sl_lock; 47 } spinlock_t; 48 49 static inline int 50 spin_is_locked(spinlock_t *spinlock) 51 { 52 return mutex_owned(&spinlock->sl_lock); 53 } 54 55 static inline void 56 spin_lock(spinlock_t *spinlock) 57 { 58 mutex_enter(&spinlock->sl_lock); 59 } 60 61 static inline void 62 spin_unlock(spinlock_t *spinlock) 63 { 64 mutex_exit(&spinlock->sl_lock); 65 } 66 67 static inline void 68 spin_lock_bh(spinlock_t *spinlock) 69 { 70 spin_lock(spinlock); 71 } 72 73 static inline void 74 spin_unlock_bh(spinlock_t *spinlock) 75 { 76 spin_unlock(spinlock); 77 } 78 79 static inline void 80 spin_lock_irq(spinlock_t *spinlock) 81 { 82 spin_lock(spinlock); 83 } 84 85 static inline void 86 spin_unlock_irq(spinlock_t *spinlock) 87 { 88 spin_unlock(spinlock); 89 } 90 91 /* Must be a macro because the second argument is to be assigned. */ 92 #define spin_lock_irqsave(SPINLOCK, FLAGS) \ 93 do { \ 94 (FLAGS) = 0; \ 95 mutex_enter(&((spinlock_t *)(SPINLOCK))->sl_lock); \ 96 } while (0) 97 98 #define spin_trylock_irqsave(SPINLOCK, FLAGS) \ 99 ( (FLAGS) = 0, \ 100 mutex_tryenter(&((spinlock_t *)(SPINLOCK))->sl_lock) ) 101 102 static inline void 103 spin_unlock_irqrestore(spinlock_t *spinlock, unsigned long __unused flags) 104 { 105 mutex_exit(&spinlock->sl_lock); 106 } 107 108 static inline void 109 spin_lock_nested(spinlock_t *spinlock, int subclass) 110 { 111 spin_lock(spinlock); 112 } 113 114 #define spin_lock_irqsave_nested(SPINLOCK, FLAGS, SUBCLASS) \ 115 spin_lock_irqsave(SPINLOCK, FLAGS) 116 117 static inline void 118 spin_lock_init(spinlock_t *spinlock) 119 { 120 /* XXX What's the right IPL? IPL_DRM...? */ 121 mutex_init(&spinlock->sl_lock, MUTEX_DEFAULT, IPL_VM); 122 } 123 124 /* 125 * XXX Linux doesn't ever destroy spin locks, it seems. We'll have to 126 * kludge it up. 127 */ 128 129 static inline void 130 spin_lock_destroy(spinlock_t *spinlock) 131 { 132 mutex_destroy(&spinlock->sl_lock); 133 } 134 135 /* This is a macro to make the panic message clearer. */ 136 #define assert_spin_locked(spinlock) \ 137 KASSERT(mutex_owned(&(spinlock)->sl_lock)) 138 139 /* 140 * Stupid reader/writer spin locks. No attempt to avoid writer 141 * starvation. Must allow recursive readers. We use mutex and state 142 * instead of compare-and-swap for expedience and LOCKDEBUG support. 143 */ 144 145 typedef struct linux_rwlock { 146 kmutex_t rw_lock; 147 unsigned rw_nreaders; 148 } rwlock_t; 149 150 static inline void 151 rwlock_init(rwlock_t *rw) 152 { 153 154 mutex_init(&rw->rw_lock, MUTEX_DEFAULT, IPL_VM); 155 rw->rw_nreaders = 0; 156 } 157 158 static inline void 159 rwlock_destroy(rwlock_t *rw) 160 { 161 162 KASSERTMSG(rw->rw_nreaders == 0, 163 "rwlock still held by %u readers", rw->rw_nreaders); 164 mutex_destroy(&rw->rw_lock); 165 } 166 167 static inline void 168 write_lock_irq(rwlock_t *rw) 169 { 170 171 for (;;) { 172 mutex_spin_enter(&rw->rw_lock); 173 if (rw->rw_nreaders == 0) 174 break; 175 mutex_spin_exit(&rw->rw_lock); 176 } 177 } 178 179 static inline void 180 write_unlock_irq(rwlock_t *rw) 181 { 182 183 KASSERT(rw->rw_nreaders == 0); 184 mutex_spin_exit(&rw->rw_lock); 185 } 186 187 static inline void 188 read_lock(rwlock_t *rw) 189 { 190 191 mutex_spin_enter(&rw->rw_lock); 192 KASSERT(rw->rw_nreaders < UINT_MAX); 193 rw->rw_nreaders++; 194 mutex_spin_exit(&rw->rw_lock); 195 } 196 197 static inline void 198 read_unlock(rwlock_t *rw) 199 { 200 201 mutex_spin_enter(&rw->rw_lock); 202 KASSERT(0 < rw->rw_nreaders); 203 rw->rw_nreaders--; 204 mutex_spin_exit(&rw->rw_lock); 205 } 206 207 static inline void 208 local_bh_disable(void) 209 { 210 } 211 212 static inline void 213 local_bh_enable(void) 214 { 215 } 216 217 #define atomic_dec_and_lock_irqsave(A, L, F) \ 218 _atomic_dec_and_lock_irqsave(A, L, &(F)) 219 220 static inline bool __must_check 221 _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, 222 unsigned long *flagsp) 223 { 224 unsigned old, new; 225 226 do { 227 old = atomic_read(atomic); 228 KASSERT(old); 229 if (old == 1) { 230 spin_lock_irqsave(lock, *flagsp); 231 if (atomic_dec_return(atomic) == 0) 232 return true; 233 spin_unlock_irqrestore(lock, *flagsp); 234 return false; 235 } 236 new = old - 1; 237 } while (atomic_cmpxchg(atomic, old, new) != old); 238 239 KASSERT(old != 1); 240 KASSERT(new != 0); 241 return false; 242 } 243 244 #endif /* _LINUX_SPINLOCK_H_ */ 245