12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394 |
- /* rwsem.h: R/W semaphores, public interface
- *
- * Written by David Howells (dhowells@redhat.com).
- * Derived from asm-i386/semaphore.h
- */
- #ifndef _LINUX_RWSEM_H
- #define _LINUX_RWSEM_H
- #include <linux/linkage.h>
- #ifdef __KERNEL__
- #include <linux/types.h>
- #include <linux/kernel.h>
- #include <asm/system.h>
- #include <asm/atomic.h>
- struct rw_semaphore;
- #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
- #include <linux/rwsem-spinlock.h> /* use a generic implementation */
- #else
- #include <asm/rwsem.h> /* use an arch-specific implementation */
- #endif
- /*
- * lock for reading
- */
- extern void down_read(struct rw_semaphore *sem);
- /*
- * trylock for reading -- returns 1 if successful, 0 if contention
- */
- extern int down_read_trylock(struct rw_semaphore *sem);
- /*
- * lock for writing
- */
- extern void down_write(struct rw_semaphore *sem);
- /*
- * trylock for writing -- returns 1 if successful, 0 if contention
- */
- extern int down_write_trylock(struct rw_semaphore *sem);
- /*
- * release a read lock
- */
- extern void up_read(struct rw_semaphore *sem);
- /*
- * release a write lock
- */
- extern void up_write(struct rw_semaphore *sem);
- /*
- * downgrade write lock to read lock
- */
- extern void downgrade_write(struct rw_semaphore *sem);
- #ifdef CONFIG_DEBUG_LOCK_ALLOC
- /*
- * nested locking. NOTE: rwsems are not allowed to recurse
- * (which occurs if the same task tries to acquire the same
- * lock instance multiple times), but multiple locks of the
- * same lock class might be taken, if the order of the locks
- * is always the same. This ordering rule can be expressed
- * to lockdep via the _nested() APIs, but enumerating the
- * subclasses that are used. (If the nesting relationship is
- * static then another method for expressing nested locking is
- * the explicit definition of lock class keys and the use of
- * lockdep_set_class() at lock initialization time.
- * See Documentation/lockdep-design.txt for more details.)
- */
- extern void down_read_nested(struct rw_semaphore *sem, int subclass);
- extern void down_write_nested(struct rw_semaphore *sem, int subclass);
- /*
- * Take/release a lock when not the owner will release it.
- *
- * [ This API should be avoided as much as possible - the
- * proper abstraction for this case is completions. ]
- */
- extern void down_read_non_owner(struct rw_semaphore *sem);
- extern void up_read_non_owner(struct rw_semaphore *sem);
- #else
- # define down_read_nested(sem, subclass) down_read(sem)
- # define down_write_nested(sem, subclass) down_write(sem)
- # define down_read_non_owner(sem) down_read(sem)
- # define up_read_non_owner(sem) up_read(sem)
- #endif
- #endif /* __KERNEL__ */
- #endif /* _LINUX_RWSEM_H */
|