[GitHub/moto-9609/android_kernel_motorola_exynos9610.git] / include / linux / rwsem.h

/* SPDX-License-Identifier: GPL-2.0 */
/* 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 <linux/atomic.h>
#include <linux/err.h>
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
#include <linux/osq_lock.h>
#endif

struct rw_semaphore;

#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
#include <linux/rwsem-spinlock.h> /* use a generic implementation */
#define __RWSEM_INIT_COUNT(name)	.count = RWSEM_UNLOCKED_VALUE
#else
/* All arch specific implementations share the same struct */
struct rw_semaphore {
	atomic_long_t count;
	struct list_head wait_list;
	raw_spinlock_t wait_lock;
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	struct optimistic_spin_queue osq; /* spinner MCS lock */
	/*
	 * Write owner. Used as a speculative check to see
	 * if the owner is running on the cpu.
	 */
	struct task_struct *owner;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map	dep_map;
#endif
};

/*
 * Setting bit 0 of the owner field with other non-zero bits will indicate
 * that the rwsem is writer-owned with an unknown owner.
 */
#define RWSEM_OWNER_UNKNOWN	((struct task_struct *)-1L)

extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);

/* Include the arch specific part */
#include <asm/rwsem.h>

/* In all implementations count != 0 means locked */
static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
	return atomic_long_read(&sem->count) != 0;
}

#define __RWSEM_INIT_COUNT(name)	.count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
#endif

/* Common initializer macros and functions */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
#else
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
#else
#define __RWSEM_OPT_INIT(lockname)
#endif

#define __RWSEM_INITIALIZER(name)				\
	{ __RWSEM_INIT_COUNT(name),				\
	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock)	\
	  __RWSEM_OPT_INIT(name)				\
	  __RWSEM_DEP_MAP_INIT(name) }

#define DECLARE_RWSEM(name) \
	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
			 struct lock_class_key *key);

#define init_rwsem(sem)						\
do {								\
	static struct lock_class_key __key;			\
								\
	__init_rwsem((sem), #sem, &__key);			\
} while (0)

/*
 * This is the same regardless of which rwsem implementation that is being used.
 * It is just a heuristic meant to be called by somebody alreadying holding the
 * rwsem to see if somebody from an incompatible type is wanting access to the
 * lock.
 */
static inline int rwsem_is_contended(struct rw_semaphore *sem)
{
	return !list_empty(&sem->wait_list);
}

/*
 * 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);
extern int __must_check down_write_killable(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/locking/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);
extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);

# define down_write_nest_lock(sem, nest_lock)			\
do {								\
	typecheck(struct lockdep_map *, &(nest_lock)->dep_map);	\
	_down_write_nest_lock(sem, &(nest_lock)->dep_map);	\
} while (0);

/*
 * 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_nest_lock(sem, nest_lock)	down_write(sem)
# define down_write_nested(sem, subclass)	down_write(sem)
# define down_write_killable_nested(sem, subclass)	down_write_killable(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
	1	/* SPDX-License-Identifier: GPL-2.0 */
	2	/* rwsem.h: R/W semaphores, public interface
	3	*
	4	* Written by David Howells (dhowells@redhat.com).
	5	* Derived from asm-i386/semaphore.h
	6	*/
	7
	8	#ifndef _LINUX_RWSEM_H
	9	#define _LINUX_RWSEM_H
	10
	11	#include <linux/linkage.h>
	12
	13	#include <linux/types.h>
	14	#include <linux/kernel.h>
	15	#include <linux/list.h>
	16	#include <linux/spinlock.h>
	17	#include <linux/atomic.h>
	18	#include <linux/err.h>
	19	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	20	#include <linux/osq_lock.h>
	21	#endif
	22
	23	struct rw_semaphore;
	24
	25	#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
	26	#include <linux/rwsem-spinlock.h> /* use a generic implementation */
	27	#define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE
	28	#else
	29	/* All arch specific implementations share the same struct */
	30	struct rw_semaphore {
	31	atomic_long_t count;
	32	struct list_head wait_list;
	33	raw_spinlock_t wait_lock;
	34	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	35	struct optimistic_spin_queue osq; /* spinner MCS lock */
	36	/*
	37	* Write owner. Used as a speculative check to see
	38	* if the owner is running on the cpu.
	39	*/
	40	struct task_struct *owner;
	41	#endif
	42	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	43	struct lockdep_map dep_map;
	44	#endif
	45	};
	46
	47	/*
	48	* Setting bit 0 of the owner field with other non-zero bits will indicate
	49	* that the rwsem is writer-owned with an unknown owner.
	50	*/
	51	#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1L)
	52
	53	extern struct rw_semaphore rwsem_down_read_failed(struct rw_semaphore sem);
	54	extern struct rw_semaphore rwsem_down_read_failed_killable(struct rw_semaphore sem);
	55	extern struct rw_semaphore rwsem_down_write_failed(struct rw_semaphore sem);
	56	extern struct rw_semaphore rwsem_down_write_failed_killable(struct rw_semaphore sem);
	57	extern struct rw_semaphore rwsem_wake(struct rw_semaphore );
	58	extern struct rw_semaphore rwsem_downgrade_wake(struct rw_semaphore sem);
	59
	60	/* Include the arch specific part */
	61	#include <asm/rwsem.h>
	62
	63	/* In all implementations count != 0 means locked */
	64	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	65	{
	66	return atomic_long_read(&sem->count) != 0;
	67	}
	68
	69	#define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
	70	#endif
	71
	72	/* Common initializer macros and functions */
	73
	74	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	75	# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
	76	#else
	77	# define __RWSEM_DEP_MAP_INIT(lockname)
	78	#endif
	79
	80	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	81	#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
	82	#else
	83	#define __RWSEM_OPT_INIT(lockname)
	84	#endif
	85
	86	#define __RWSEM_INITIALIZER(name) \
	87	{ __RWSEM_INIT_COUNT(name), \
	88	.wait_list = LIST_HEAD_INIT((name).wait_list), \
	89	.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
	90	__RWSEM_OPT_INIT(name) \
	91	__RWSEM_DEP_MAP_INIT(name) }
	92
	93	#define DECLARE_RWSEM(name) \
	94	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
	95
	96	extern void __init_rwsem(struct rw_semaphore sem, const char name,
	97	struct lock_class_key *key);
	98
	99	#define init_rwsem(sem) \
	100	do { \
	101	static struct lock_class_key __key; \
	102	\
	103	__init_rwsem((sem), #sem, &__key); \
	104	} while (0)
	105
	106	/*
	107	* This is the same regardless of which rwsem implementation that is being used.
	108	* It is just a heuristic meant to be called by somebody alreadying holding the
	109	* rwsem to see if somebody from an incompatible type is wanting access to the
	110	* lock.
	111	*/
	112	static inline int rwsem_is_contended(struct rw_semaphore *sem)
	113	{
	114	return !list_empty(&sem->wait_list);
	115	}
	116
	117	/*
	118	* lock for reading
	119	*/
	120	extern void down_read(struct rw_semaphore *sem);
	121
	122	/*
	123	* trylock for reading -- returns 1 if successful, 0 if contention
	124	*/
	125	extern int down_read_trylock(struct rw_semaphore *sem);
	126
	127	/*
	128	* lock for writing
	129	*/
	130	extern void down_write(struct rw_semaphore *sem);
	131	extern int __must_check down_write_killable(struct rw_semaphore *sem);
	132
	133	/*
	134	* trylock for writing -- returns 1 if successful, 0 if contention
	135	*/
	136	extern int down_write_trylock(struct rw_semaphore *sem);
	137
	138	/*
	139	* release a read lock
	140	*/
	141	extern void up_read(struct rw_semaphore *sem);
	142
	143	/*
	144	* release a write lock
	145	*/
	146	extern void up_write(struct rw_semaphore *sem);
	147
	148	/*
	149	* downgrade write lock to read lock
	150	*/
	151	extern void downgrade_write(struct rw_semaphore *sem);
	152
	153	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	154	/*
	155	* nested locking. NOTE: rwsems are not allowed to recurse
	156	* (which occurs if the same task tries to acquire the same
	157	* lock instance multiple times), but multiple locks of the
	158	* same lock class might be taken, if the order of the locks
	159	* is always the same. This ordering rule can be expressed
	160	* to lockdep via the _nested() APIs, but enumerating the
	161	* subclasses that are used. (If the nesting relationship is
	162	* static then another method for expressing nested locking is
	163	* the explicit definition of lock class keys and the use of
	164	* lockdep_set_class() at lock initialization time.
	165	* See Documentation/locking/lockdep-design.txt for more details.)
	166	*/
	167	extern void down_read_nested(struct rw_semaphore *sem, int subclass);
	168	extern void down_write_nested(struct rw_semaphore *sem, int subclass);
	169	extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
	170	extern void _down_write_nest_lock(struct rw_semaphore sem, struct lockdep_map nest_lock);
	171
	172	# define down_write_nest_lock(sem, nest_lock) \
	173	do { \
	174	typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
	175	_down_write_nest_lock(sem, &(nest_lock)->dep_map); \
	176	} while (0);
	177
	178	/*
	179	* Take/release a lock when not the owner will release it.
	180	*
	181	* [ This API should be avoided as much as possible - the
	182	* proper abstraction for this case is completions. ]
	183	*/
	184	extern void down_read_non_owner(struct rw_semaphore *sem);
	185	extern void up_read_non_owner(struct rw_semaphore *sem);
	186	#else
	187	# define down_read_nested(sem, subclass) down_read(sem)
	188	# define down_write_nest_lock(sem, nest_lock) down_write(sem)
	189	# define down_write_nested(sem, subclass) down_write(sem)
	190	# define down_write_killable_nested(sem, subclass) down_write_killable(sem)
	191	# define down_read_non_owner(sem) down_read(sem)
	192	# define up_read_non_owner(sem) up_read(sem)
	193	#endif
	194
	195	#endif /* _LINUX_RWSEM_H */