1 // SPDX-License-Identifier: GPL-2.0 2 /* kernel/rwsem.c: R/W semaphores, public implementation 3 * 4 * Written by David Howells (dhowells@redhat.com). 5 * Derived from asm-i386/semaphore.h 6 */ 7 8 #include <linux/types.h> 9 #include <linux/kernel.h> 10 #include <linux/sched.h> 11 #include <linux/sched/debug.h> 12 #include <linux/export.h> 13 #include <linux/rwsem.h> 14 #include <linux/atomic.h> 15 16 #include "rwsem.h" 17 18 /* 19 * lock for reading 20 */ 21 void __sched down_read(struct rw_semaphore *sem) 22 { 23 might_sleep(); 24 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); 25 26 LOCK_CONTENDED(sem, __down_read_trylock, __down_read); 27 rwsem_set_reader_owned(sem); 28 } 29 30 EXPORT_SYMBOL(down_read); 31 32 /* 33 * trylock for reading -- returns 1 if successful, 0 if contention 34 */ 35 int down_read_trylock(struct rw_semaphore *sem) 36 { 37 int ret = __down_read_trylock(sem); 38 39 if (ret == 1) { 40 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); 41 rwsem_set_reader_owned(sem); 42 } 43 return ret; 44 } 45 46 EXPORT_SYMBOL(down_read_trylock); 47 48 /* 49 * lock for writing 50 */ 51 void __sched down_write(struct rw_semaphore *sem) 52 { 53 might_sleep(); 54 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); 55 56 LOCK_CONTENDED(sem, __down_write_trylock, __down_write); 57 rwsem_set_owner(sem); 58 } 59 60 EXPORT_SYMBOL(down_write); 61 62 /* 63 * lock for writing 64 */ 65 int __sched down_write_killable(struct rw_semaphore *sem) 66 { 67 might_sleep(); 68 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); 69 70 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { 71 rwsem_release(&sem->dep_map, 1, _RET_IP_); 72 return -EINTR; 73 } 74 75 rwsem_set_owner(sem); 76 return 0; 77 } 78 79 EXPORT_SYMBOL(down_write_killable); 80 81 /* 82 * trylock for writing -- returns 1 if successful, 0 if contention 83 */ 84 int down_write_trylock(struct rw_semaphore *sem) 85 { 86 int ret = __down_write_trylock(sem); 87 88 if (ret == 1) { 89 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); 90 rwsem_set_owner(sem); 91 } 92 93 return ret; 94 } 95 96 EXPORT_SYMBOL(down_write_trylock); 97 98 /* 99 * release a read lock 100 */ 101 void up_read(struct rw_semaphore *sem) 102 { 103 rwsem_release(&sem->dep_map, 1, _RET_IP_); 104 105 __up_read(sem); 106 } 107 108 EXPORT_SYMBOL(up_read); 109 110 /* 111 * release a write lock 112 */ 113 void up_write(struct rw_semaphore *sem) 114 { 115 rwsem_release(&sem->dep_map, 1, _RET_IP_); 116 117 rwsem_clear_owner(sem); 118 __up_write(sem); 119 } 120 121 EXPORT_SYMBOL(up_write); 122 123 /* 124 * downgrade write lock to read lock 125 */ 126 void downgrade_write(struct rw_semaphore *sem) 127 { 128 lock_downgrade(&sem->dep_map, _RET_IP_); 129 130 rwsem_set_reader_owned(sem); 131 __downgrade_write(sem); 132 } 133 134 EXPORT_SYMBOL(downgrade_write); 135 136 #ifdef CONFIG_DEBUG_LOCK_ALLOC 137 138 void down_read_nested(struct rw_semaphore *sem, int subclass) 139 { 140 might_sleep(); 141 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); 142 143 LOCK_CONTENDED(sem, __down_read_trylock, __down_read); 144 rwsem_set_reader_owned(sem); 145 } 146 147 EXPORT_SYMBOL(down_read_nested); 148 149 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) 150 { 151 might_sleep(); 152 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_); 153 154 LOCK_CONTENDED(sem, __down_write_trylock, __down_write); 155 rwsem_set_owner(sem); 156 } 157 158 EXPORT_SYMBOL(_down_write_nest_lock); 159 160 void down_read_non_owner(struct rw_semaphore *sem) 161 { 162 might_sleep(); 163 164 __down_read(sem); 165 } 166 167 EXPORT_SYMBOL(down_read_non_owner); 168 169 void down_write_nested(struct rw_semaphore *sem, int subclass) 170 { 171 might_sleep(); 172 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); 173 174 LOCK_CONTENDED(sem, __down_write_trylock, __down_write); 175 rwsem_set_owner(sem); 176 } 177 178 EXPORT_SYMBOL(down_write_nested); 179 180 int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass) 181 { 182 might_sleep(); 183 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); 184 185 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) { 186 rwsem_release(&sem->dep_map, 1, _RET_IP_); 187 return -EINTR; 188 } 189 190 rwsem_set_owner(sem); 191 return 0; 192 } 193 194 EXPORT_SYMBOL(down_write_killable_nested); 195 196 void up_read_non_owner(struct rw_semaphore *sem) 197 { 198 __up_read(sem); 199 } 200 201 EXPORT_SYMBOL(up_read_non_owner); 202 203 #endif 204 205 206