1 /* kernel/rwsem.c: R/W semaphores, public implementation
3 * Written by David Howells (dhowells@redhat.com).
4 * Derived from asm-i386/semaphore.h
7 #include <linux/types.h>
8 #include <linux/kernel.h>
9 #include <linux/sched.h>
10 #include <linux/export.h>
11 #include <linux/rwsem.h>
12 #include <linux/atomic.h>
19 void __sched
down_read(struct rw_semaphore
*sem
)
22 rwsem_acquire_read(&sem
->dep_map
, 0, 0, _RET_IP_
);
24 LOCK_CONTENDED(sem
, __down_read_trylock
, __down_read
);
27 EXPORT_SYMBOL(down_read
);
30 * trylock for reading -- returns 1 if successful, 0 if contention
32 int down_read_trylock(struct rw_semaphore
*sem
)
34 int ret
= __down_read_trylock(sem
);
37 rwsem_acquire_read(&sem
->dep_map
, 0, 1, _RET_IP_
);
41 EXPORT_SYMBOL(down_read_trylock
);
46 void __sched
down_write(struct rw_semaphore
*sem
)
49 rwsem_acquire(&sem
->dep_map
, 0, 0, _RET_IP_
);
51 LOCK_CONTENDED(sem
, __down_write_trylock
, __down_write
);
55 EXPORT_SYMBOL(down_write
);
60 int __sched
down_write_killable(struct rw_semaphore
*sem
)
63 rwsem_acquire(&sem
->dep_map
, 0, 0, _RET_IP_
);
65 if (LOCK_CONTENDED_RETURN(sem
, __down_write_trylock
, __down_write_killable
)) {
66 rwsem_release(&sem
->dep_map
, 1, _RET_IP_
);
74 EXPORT_SYMBOL(down_write_killable
);
77 * trylock for writing -- returns 1 if successful, 0 if contention
79 int down_write_trylock(struct rw_semaphore
*sem
)
81 int ret
= __down_write_trylock(sem
);
84 rwsem_acquire(&sem
->dep_map
, 0, 1, _RET_IP_
);
91 EXPORT_SYMBOL(down_write_trylock
);
96 void up_read(struct rw_semaphore
*sem
)
98 rwsem_release(&sem
->dep_map
, 1, _RET_IP_
);
103 EXPORT_SYMBOL(up_read
);
106 * release a write lock
108 void up_write(struct rw_semaphore
*sem
)
110 rwsem_release(&sem
->dep_map
, 1, _RET_IP_
);
112 rwsem_clear_owner(sem
);
116 EXPORT_SYMBOL(up_write
);
119 * downgrade write lock to read lock
121 void downgrade_write(struct rw_semaphore
*sem
)
124 * lockdep: a downgraded write will live on as a write
127 rwsem_clear_owner(sem
);
128 __downgrade_write(sem
);
131 EXPORT_SYMBOL(downgrade_write
);
133 #ifdef CONFIG_DEBUG_LOCK_ALLOC
135 void down_read_nested(struct rw_semaphore
*sem
, int subclass
)
138 rwsem_acquire_read(&sem
->dep_map
, subclass
, 0, _RET_IP_
);
140 LOCK_CONTENDED(sem
, __down_read_trylock
, __down_read
);
143 EXPORT_SYMBOL(down_read_nested
);
145 void _down_write_nest_lock(struct rw_semaphore
*sem
, struct lockdep_map
*nest
)
148 rwsem_acquire_nest(&sem
->dep_map
, 0, 0, nest
, _RET_IP_
);
150 LOCK_CONTENDED(sem
, __down_write_trylock
, __down_write
);
151 rwsem_set_owner(sem
);
154 EXPORT_SYMBOL(_down_write_nest_lock
);
156 void down_read_non_owner(struct rw_semaphore
*sem
)
163 EXPORT_SYMBOL(down_read_non_owner
);
165 void down_write_nested(struct rw_semaphore
*sem
, int subclass
)
168 rwsem_acquire(&sem
->dep_map
, subclass
, 0, _RET_IP_
);
170 LOCK_CONTENDED(sem
, __down_write_trylock
, __down_write
);
171 rwsem_set_owner(sem
);
174 EXPORT_SYMBOL(down_write_nested
);
176 int __sched
down_write_killable_nested(struct rw_semaphore
*sem
, int subclass
)
179 rwsem_acquire(&sem
->dep_map
, subclass
, 0, _RET_IP_
);
181 if (LOCK_CONTENDED_RETURN(sem
, __down_write_trylock
, __down_write_killable
)) {
182 rwsem_release(&sem
->dep_map
, 1, _RET_IP_
);
186 rwsem_set_owner(sem
);
190 EXPORT_SYMBOL(down_write_killable_nested
);
192 void up_read_non_owner(struct rw_semaphore
*sem
)
197 EXPORT_SYMBOL(up_read_non_owner
);