1 // SPDX-License-Identifier: GPL-2.0
2 /* kernel/rwsem.c: R/W semaphores, public implementation
4 * Written by David Howells (dhowells@redhat.com).
5 * Derived from asm-i386/semaphore.h
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>
21 void __sched down_read(struct rw_semaphore *sem)
24 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
26 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
27 rwsem_set_reader_owned(sem);
30 EXPORT_SYMBOL(down_read);
32 int __sched down_read_killable(struct rw_semaphore *sem)
35 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
37 if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
38 rwsem_release(&sem->dep_map, 1, _RET_IP_);
42 rwsem_set_reader_owned(sem);
46 EXPORT_SYMBOL(down_read_killable);
49 * trylock for reading -- returns 1 if successful, 0 if contention
51 int down_read_trylock(struct rw_semaphore *sem)
53 int ret = __down_read_trylock(sem);
56 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
57 rwsem_set_reader_owned(sem);
62 EXPORT_SYMBOL(down_read_trylock);
67 void __sched down_write(struct rw_semaphore *sem)
70 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
72 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
76 EXPORT_SYMBOL(down_write);
81 int __sched down_write_killable(struct rw_semaphore *sem)
84 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
86 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
87 rwsem_release(&sem->dep_map, 1, _RET_IP_);
95 EXPORT_SYMBOL(down_write_killable);
98 * trylock for writing -- returns 1 if successful, 0 if contention
100 int down_write_trylock(struct rw_semaphore *sem)
102 int ret = __down_write_trylock(sem);
105 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_);
106 rwsem_set_owner(sem);
112 EXPORT_SYMBOL(down_write_trylock);
115 * release a read lock
117 void up_read(struct rw_semaphore *sem)
119 rwsem_release(&sem->dep_map, 1, _RET_IP_);
120 DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED));
122 rwsem_clear_reader_owned(sem);
126 EXPORT_SYMBOL(up_read);
129 * release a write lock
131 void up_write(struct rw_semaphore *sem)
133 rwsem_release(&sem->dep_map, 1, _RET_IP_);
134 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
136 rwsem_clear_owner(sem);
140 EXPORT_SYMBOL(up_write);
143 * downgrade write lock to read lock
145 void downgrade_write(struct rw_semaphore *sem)
147 lock_downgrade(&sem->dep_map, _RET_IP_);
148 DEBUG_RWSEMS_WARN_ON(sem->owner != current);
150 rwsem_set_reader_owned(sem);
151 __downgrade_write(sem);
154 EXPORT_SYMBOL(downgrade_write);
156 #ifdef CONFIG_DEBUG_LOCK_ALLOC
158 void down_read_nested(struct rw_semaphore *sem, int subclass)
161 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
163 LOCK_CONTENDED(sem, __down_read_trylock, __down_read);
164 rwsem_set_reader_owned(sem);
167 EXPORT_SYMBOL(down_read_nested);
169 void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest)
172 rwsem_acquire_nest(&sem->dep_map, 0, 0, nest, _RET_IP_);
174 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
175 rwsem_set_owner(sem);
178 EXPORT_SYMBOL(_down_write_nest_lock);
180 void down_read_non_owner(struct rw_semaphore *sem)
185 __rwsem_set_reader_owned(sem, NULL);
188 EXPORT_SYMBOL(down_read_non_owner);
190 void down_write_nested(struct rw_semaphore *sem, int subclass)
193 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
195 LOCK_CONTENDED(sem, __down_write_trylock, __down_write);
196 rwsem_set_owner(sem);
199 EXPORT_SYMBOL(down_write_nested);
201 int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass)
204 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
206 if (LOCK_CONTENDED_RETURN(sem, __down_write_trylock, __down_write_killable)) {
207 rwsem_release(&sem->dep_map, 1, _RET_IP_);
211 rwsem_set_owner(sem);
215 EXPORT_SYMBOL(down_write_killable_nested);
217 void up_read_non_owner(struct rw_semaphore *sem)
219 DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED));
223 EXPORT_SYMBOL(up_read_non_owner);