kernel/locking/rwsem.c

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