/* kernel/rwsem.c: R/W semaphores, public implementation * * Written by David Howells (dhowells@redhat.com). * Derived from asm-i386/semaphore.h */ #include <linux/types.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/export.h> #include <linux/rwsem.h> #include <asm/system.h> #include <linux/atomic.h> /* * lock for reading */ void __sched down_read(struct rw_semaphore *sem) { might_sleep(); rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_read_trylock, __down_read); } EXPORT_SYMBOL(down_read); /* * trylock for reading -- returns 1 if successful, 0 if contention */ int down_read_trylock(struct rw_semaphore *sem) { int ret = __down_read_trylock(sem); if (ret == 1) rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); return ret; } EXPORT_SYMBOL(down_read_trylock); /* * lock for writing */ void __sched down_write(struct rw_semaphore *sem) { might_sleep(); rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_write_trylock, __down_write); } EXPORT_SYMBOL(down_write); /* * trylock for writing -- returns 1 if successful, 0 if contention */ int down_write_trylock(struct rw_semaphore *sem) { int ret = __down_write_trylock(sem); if (ret == 1) rwsem_acquire(&sem->dep_map, 0, 1, _RET_IP_); return ret; } EXPORT_SYMBOL(down_write_trylock); /* * release a read lock */ void up_read(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); __up_read(sem); } EXPORT_SYMBOL(up_read); /* * release a write lock */ void up_write(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); __up_write(sem); } EXPORT_SYMBOL(up_write); /* * downgrade write lock to read lock */ void downgrade_write(struct rw_semaphore *sem) { /* * lockdep: a downgraded write will live on as a write * dependency. */ __downgrade_write(sem); } EXPORT_SYMBOL(downgrade_write); #ifdef CONFIG_DEBUG_LOCK_ALLOC void down_read_nested(struct rw_semaphore *sem, int subclass) { might_sleep(); rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_read_trylock, __down_read); } EXPORT_SYMBOL(down_read_nested); void down_write_nested(struct rw_semaphore *sem, int subclass) { might_sleep(); rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_); LOCK_CONTENDED(sem, __down_write_trylock, __down_write); } EXPORT_SYMBOL(down_write_nested); #endif