[GitHub/mt8127/android_kernel_alcatel_ttab.git] / include / linux / rwsem.h

/* 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 <linux/list.h>
#include <linux/spinlock.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
/* All arch specific implementations share the same struct */
struct rw_semaphore {
	long			count;
	spinlock_t		wait_lock;
	struct list_head	wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map	dep_map;
#endif
};

/* Include the arch specific part */
#include <asm/rwsem.h>
#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 */
Commit	Line	Data
1da177e4 LT	1	/* rwsem.h: R/W semaphores, public interface
	2	*
	3	* Written by David Howells (dhowells@redhat.com).
	4	* Derived from asm-i386/semaphore.h
	5	*/
	6
	7	#ifndef _LINUX_RWSEM_H
	8	#define _LINUX_RWSEM_H
	9
	10	#include <linux/linkage.h>
	11
1da177e4 LT	12	#include <linux/types.h>
1da177e4 LT	13	#include <linux/kernel.h>
c16a87ce TG	14	#include <linux/list.h>
	15	#include <linux/spinlock.h>
	16
1da177e4 LT	17	#include <asm/system.h>
	18	#include <asm/atomic.h>
	19
	20	struct rw_semaphore;
	21
	22	#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
	23	#include <linux/rwsem-spinlock.h> /* use a generic implementation */
	24	#else
1c8ed640 TG	25	/* All arch specific implementations share the same struct */
	26	struct rw_semaphore {
	27	long count;
	28	spinlock_t wait_lock;
	29	struct list_head wait_list;
	30	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	31	struct lockdep_map dep_map;
	32	#endif
	33	};
	34
	35	/* Include the arch specific part */
	36	#include <asm/rwsem.h>
1da177e4 LT	37	#endif
1da177e4 LT	38
1da177e4 LT	39	/*
	40	* lock for reading
	41	*/
4ea2176d	42	extern void down_read(struct rw_semaphore *sem);
1da177e4 LT	43
	44	/*
	45	* trylock for reading -- returns 1 if successful, 0 if contention
	46	*/
4ea2176d	47	extern int down_read_trylock(struct rw_semaphore *sem);
1da177e4 LT	48
	49	/*
	50	* lock for writing
	51	*/
4ea2176d	52	extern void down_write(struct rw_semaphore *sem);
1da177e4 LT	53
	54	/*
	55	* trylock for writing -- returns 1 if successful, 0 if contention
	56	*/
4ea2176d	57	extern int down_write_trylock(struct rw_semaphore *sem);
1da177e4 LT	58
	59	/*
	60	* release a read lock
	61	*/
4ea2176d	62	extern void up_read(struct rw_semaphore *sem);
1da177e4 LT	63
	64	/*
	65	* release a write lock
	66	*/
4ea2176d	67	extern void up_write(struct rw_semaphore *sem);
1da177e4 LT	68
	69	/*
	70	* downgrade write lock to read lock
	71	*/
4ea2176d IM	72	extern void downgrade_write(struct rw_semaphore *sem);
	73
	74	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	75	/*
5fca80e8 IM	76	* nested locking. NOTE: rwsems are not allowed to recurse
	77	* (which occurs if the same task tries to acquire the same
	78	* lock instance multiple times), but multiple locks of the
	79	* same lock class might be taken, if the order of the locks
	80	* is always the same. This ordering rule can be expressed
	81	* to lockdep via the _nested() APIs, but enumerating the
	82	* subclasses that are used. (If the nesting relationship is
	83	* static then another method for expressing nested locking is
	84	* the explicit definition of lock class keys and the use of
	85	* lockdep_set_class() at lock initialization time.
	86	* See Documentation/lockdep-design.txt for more details.)
4ea2176d IM	87	*/
	88	extern void down_read_nested(struct rw_semaphore *sem, int subclass);
	89	extern void down_write_nested(struct rw_semaphore *sem, int subclass);
	90	/*
5fca80e8 IM	91	* Take/release a lock when not the owner will release it.
	92	*
	93	* [ This API should be avoided as much as possible - the
	94	* proper abstraction for this case is completions. ]
4ea2176d IM	95	*/
	96	extern void down_read_non_owner(struct rw_semaphore *sem);
	97	extern void up_read_non_owner(struct rw_semaphore *sem);
	98	#else
	99	# define down_read_nested(sem, subclass) down_read(sem)
	100	# define down_write_nested(sem, subclass) down_write(sem)
	101	# define down_read_non_owner(sem) down_read(sem)
	102	# define up_read_non_owner(sem) up_read(sem)
	103	#endif
1da177e4	104
1da177e4	105	#endif /* _LINUX_RWSEM_H */