blob: dd1d142503404da2775808630bda2021a597229e [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#include <linux/types.h>
13#include <linux/kernel.h>
Thomas Gleixnerc16a87c2011-01-26 20:05:50 +000014#include <linux/list.h>
15#include <linux/spinlock.h>
Arun Sharma600634972011-07-26 16:09:06 -070016#include <linux/atomic.h>
Michal Hockod4799602016-04-07 17:12:26 +020017#include <linux/err.h>
Davidlohr Bueso5db6c6f2014-07-11 14:00:06 -070018#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
Jason Low90631822014-07-14 10:27:49 -070019#include <linux/osq_lock.h>
Davidlohr Bueso5db6c6f2014-07-11 14:00:06 -070020#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
22struct rw_semaphore;
23
24#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
25#include <linux/rwsem-spinlock.h> /* use a generic implementation */
Jason Low8ee62b12016-06-03 22:26:02 -070026#define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE
Linus Torvalds1da177e2005-04-16 15:20:36 -070027#else
Thomas Gleixner1c8ed642011-01-26 20:05:56 +000028/* All arch specific implementations share the same struct */
29struct rw_semaphore {
Jason Low8ee62b12016-06-03 22:26:02 -070030 atomic_long_t count;
Davidlohr Bueso4fc828e2014-05-02 11:24:15 -070031 struct list_head wait_list;
Jason Lowce069fc2014-07-14 10:27:52 -070032 raw_spinlock_t wait_lock;
Davidlohr Bueso5db6c6f2014-07-11 14:00:06 -070033#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
Jason Lowce069fc2014-07-14 10:27:52 -070034 struct optimistic_spin_queue osq; /* spinner MCS lock */
Davidlohr Bueso4fc828e2014-05-02 11:24:15 -070035 /*
36 * Write owner. Used as a speculative check to see
37 * if the owner is running on the cpu.
38 */
39 struct task_struct *owner;
Davidlohr Bueso4fc828e2014-05-02 11:24:15 -070040#endif
Thomas Gleixner1c8ed642011-01-26 20:05:56 +000041#ifdef CONFIG_DEBUG_LOCK_ALLOC
42 struct lockdep_map dep_map;
43#endif
44};
45
Thomas Gleixnerd1233752011-01-26 21:32:01 +010046extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
47extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
Michal Hockod4799602016-04-07 17:12:26 +020048extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);
Thomas Gleixnerd1233752011-01-26 21:32:01 +010049extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
50extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
Thomas Gleixneraac72272011-01-26 20:06:06 +000051
Thomas Gleixner1c8ed642011-01-26 20:05:56 +000052/* Include the arch specific part */
53#include <asm/rwsem.h>
Thomas Gleixner41e58872011-01-26 20:06:03 +000054
55/* In all implementations count != 0 means locked */
56static inline int rwsem_is_locked(struct rw_semaphore *sem)
57{
Jason Low8ee62b12016-06-03 22:26:02 -070058 return atomic_long_read(&sem->count) != 0;
Thomas Gleixner41e58872011-01-26 20:06:03 +000059}
60
Jason Low8ee62b12016-06-03 22:26:02 -070061#define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
Linus Torvalds1da177e2005-04-16 15:20:36 -070062#endif
63
Thomas Gleixner12249b32011-01-26 20:06:00 +000064/* Common initializer macros and functions */
65
66#ifdef CONFIG_DEBUG_LOCK_ALLOC
67# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
68#else
69# define __RWSEM_DEP_MAP_INIT(lockname)
70#endif
71
Davidlohr Bueso5db6c6f2014-07-11 14:00:06 -070072#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
Jason Lowce069fc2014-07-14 10:27:52 -070073#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
Davidlohr Bueso4fc828e2014-05-02 11:24:15 -070074#else
Jason Lowce069fc2014-07-14 10:27:52 -070075#define __RWSEM_OPT_INIT(lockname)
Davidlohr Bueso4fc828e2014-05-02 11:24:15 -070076#endif
Thomas Gleixner12249b32011-01-26 20:06:00 +000077
Jason Lowce069fc2014-07-14 10:27:52 -070078#define __RWSEM_INITIALIZER(name) \
Jason Low8ee62b12016-06-03 22:26:02 -070079 { __RWSEM_INIT_COUNT(name), \
Jason Lowce069fc2014-07-14 10:27:52 -070080 .wait_list = LIST_HEAD_INIT((name).wait_list), \
81 .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
82 __RWSEM_OPT_INIT(name) \
83 __RWSEM_DEP_MAP_INIT(name) }
84
Thomas Gleixner12249b32011-01-26 20:06:00 +000085#define DECLARE_RWSEM(name) \
86 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
87
88extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
89 struct lock_class_key *key);
90
91#define init_rwsem(sem) \
92do { \
93 static struct lock_class_key __key; \
94 \
95 __init_rwsem((sem), #sem, &__key); \
96} while (0)
97
Linus Torvalds1da177e2005-04-16 15:20:36 -070098/*
Josef Bacik4a444b12013-08-30 10:05:22 -040099 * This is the same regardless of which rwsem implementation that is being used.
100 * It is just a heuristic meant to be called by somebody alreadying holding the
101 * rwsem to see if somebody from an incompatible type is wanting access to the
102 * lock.
103 */
104static inline int rwsem_is_contended(struct rw_semaphore *sem)
105{
106 return !list_empty(&sem->wait_list);
107}
108
109/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 * lock for reading
111 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700112extern void down_read(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113
114/*
115 * trylock for reading -- returns 1 if successful, 0 if contention
116 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700117extern int down_read_trylock(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
119/*
120 * lock for writing
121 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700122extern void down_write(struct rw_semaphore *sem);
Michal Hocko916633a2016-04-07 17:12:31 +0200123extern int __must_check down_write_killable(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124
125/*
126 * trylock for writing -- returns 1 if successful, 0 if contention
127 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700128extern int down_write_trylock(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
130/*
131 * release a read lock
132 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700133extern void up_read(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
135/*
136 * release a write lock
137 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700138extern void up_write(struct rw_semaphore *sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139
140/*
141 * downgrade write lock to read lock
142 */
Ingo Molnar4ea21762006-07-03 00:24:53 -0700143extern void downgrade_write(struct rw_semaphore *sem);
144
145#ifdef CONFIG_DEBUG_LOCK_ALLOC
146/*
Ingo Molnar5fca80e2006-07-10 04:44:02 -0700147 * nested locking. NOTE: rwsems are not allowed to recurse
148 * (which occurs if the same task tries to acquire the same
149 * lock instance multiple times), but multiple locks of the
150 * same lock class might be taken, if the order of the locks
151 * is always the same. This ordering rule can be expressed
152 * to lockdep via the _nested() APIs, but enumerating the
153 * subclasses that are used. (If the nesting relationship is
154 * static then another method for expressing nested locking is
155 * the explicit definition of lock class keys and the use of
156 * lockdep_set_class() at lock initialization time.
Davidlohr Bueso214e0ae2014-07-30 13:41:55 -0700157 * See Documentation/locking/lockdep-design.txt for more details.)
Ingo Molnar4ea21762006-07-03 00:24:53 -0700158 */
159extern void down_read_nested(struct rw_semaphore *sem, int subclass);
160extern void down_write_nested(struct rw_semaphore *sem, int subclass);
Al Viro887bddf2016-05-26 00:04:58 -0400161extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass);
Jiri Kosina1b963c82013-01-11 14:31:56 -0800162extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock);
163
164# define down_write_nest_lock(sem, nest_lock) \
165do { \
166 typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
167 _down_write_nest_lock(sem, &(nest_lock)->dep_map); \
168} while (0);
169
Kent Overstreet84759c62011-09-21 21:43:05 -0700170/*
171 * Take/release a lock when not the owner will release it.
172 *
173 * [ This API should be avoided as much as possible - the
174 * proper abstraction for this case is completions. ]
175 */
176extern void down_read_non_owner(struct rw_semaphore *sem);
177extern void up_read_non_owner(struct rw_semaphore *sem);
Ingo Molnar4ea21762006-07-03 00:24:53 -0700178#else
179# define down_read_nested(sem, subclass) down_read(sem)
Jiri Kosinae65b9ad2013-01-15 20:12:37 +0100180# define down_write_nest_lock(sem, nest_lock) down_write(sem)
Ingo Molnar4ea21762006-07-03 00:24:53 -0700181# define down_write_nested(sem, subclass) down_write(sem)
Al Viro887bddf2016-05-26 00:04:58 -0400182# define down_write_killable_nested(sem, subclass) down_write_killable(sem)
Kent Overstreet84759c62011-09-21 21:43:05 -0700183# define down_read_non_owner(sem) down_read(sem)
184# define up_read_non_owner(sem) up_read(sem)
Ingo Molnar4ea21762006-07-03 00:24:53 -0700185#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187#endif /* _LINUX_RWSEM_H */