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/module.h> 11#include <linux/rwsem.h> 12 13#include <asm/system.h> 14#include <asm/atomic.h> 15 16/* 17 * lock for reading 18 */ 19void __sched down_read(struct rw_semaphore *sem) 20{ 21 might_sleep(); 22 rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); 23 24 LOCK_CONTENDED(sem, __down_read_trylock, __down_read); 25} 26 27EXPORT_SYMBOL(down_read); 28 29/* 30 * trylock for reading -- returns 1 if successful, 0 if contention 31 */ 32int down_read_trylock(struct rw_semaphore *sem) 33{ 34 int ret = __down_read_trylock(sem); 35 36 if (ret == 1) 37 rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); 38 return ret; 39} 40 41EXPORT_SYMBOL(down_read_trylock); 42 43/* 44 * lock for writing 45 */ 46void __sched down_write(struct rw_semaphore *sem) 47{ 48 might_sleep(); 49 rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); 50 51 LOCK_CONTENDED(sem, __down_write_trylock, __down_write); 52} 53 54EXPORT_SYMBOL(down_write); 55 56/* 57 * trylock for writing -- returns 1 if successful, 0 if contention 58 */ 59int down_write_trylock(struct rw_semaphore *sem) 60{ 61 int ret = __down_write_trylock(sem); 62 63 if (ret == 1) 64 rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); 65 return ret; 66} 67 68EXPORT_SYMBOL(down_write_trylock); 69 70/* 71 * release a read lock 72 */ 73void up_read(struct rw_semaphore *sem) 74{ 75 rwsem_release(&sem->dep_map, 1, _RET_IP_); 76 77 __up_read(sem); 78} 79 80EXPORT_SYMBOL(up_read); 81 82/* 83 * release a write lock 84 */ 85void up_write(struct rw_semaphore *sem) 86{ 87 rwsem_release(&sem->dep_map, 1, _RET_IP_); 88 89 __up_write(sem); 90} 91 92EXPORT_SYMBOL(up_write); 93 94/* 95 * downgrade write lock to read lock 96 */ 97void downgrade_write(struct rw_semaphore *sem) 98{ 99 /* 100 * lockdep: a downgraded write will live on as a write 101 * dependency. 102 */ 103 __downgrade_write(sem); 104} 105 106EXPORT_SYMBOL(downgrade_write); 107 108#ifdef CONFIG_DEBUG_LOCK_ALLOC 109 110void down_read_nested(struct rw_semaphore *sem, int subclass) 111{ 112 might_sleep(); 113 rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); 114 115 LOCK_CONTENDED(sem, __down_read_trylock, __down_read); 116} 117 118EXPORT_SYMBOL(down_read_nested); 119 120void down_read_non_owner(struct rw_semaphore *sem) 121{ 122 might_sleep(); 123 124 __down_read(sem); 125} 126 127EXPORT_SYMBOL(down_read_non_owner); 128 129void down_write_nested(struct rw_semaphore *sem, int subclass) 130{ 131 might_sleep(); 132 rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); 133 134 LOCK_CONTENDED(sem, __down_write_trylock, __down_write); 135} 136 137EXPORT_SYMBOL(down_write_nested); 138 139void up_read_non_owner(struct rw_semaphore *sem) 140{ 141 __up_read(sem); 142} 143 144EXPORT_SYMBOL(up_read_non_owner); 145 146#endif 147