92 lines
2.5 KiB
C
92 lines
2.5 KiB
C
/* 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>
|
|
|
|
#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 /* _LINUX_RWSEM_H */
|