treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157
[sfrench/cifs-2.6.git] / include / asm-generic / qspinlock.h
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * Queued spinlock
4  *
5  * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
6  * (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
7  *
8  * Authors: Waiman Long <waiman.long@hpe.com>
9  */
10 #ifndef __ASM_GENERIC_QSPINLOCK_H
11 #define __ASM_GENERIC_QSPINLOCK_H
12
13 #include <asm-generic/qspinlock_types.h>
14
15 /**
16  * queued_spin_is_locked - is the spinlock locked?
17  * @lock: Pointer to queued spinlock structure
18  * Return: 1 if it is locked, 0 otherwise
19  */
20 static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
21 {
22         /*
23          * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
24          * isn't immediately observable.
25          */
26         return atomic_read(&lock->val);
27 }
28
29 /**
30  * queued_spin_value_unlocked - is the spinlock structure unlocked?
31  * @lock: queued spinlock structure
32  * Return: 1 if it is unlocked, 0 otherwise
33  *
34  * N.B. Whenever there are tasks waiting for the lock, it is considered
35  *      locked wrt the lockref code to avoid lock stealing by the lockref
36  *      code and change things underneath the lock. This also allows some
37  *      optimizations to be applied without conflict with lockref.
38  */
39 static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
40 {
41         return !atomic_read(&lock.val);
42 }
43
44 /**
45  * queued_spin_is_contended - check if the lock is contended
46  * @lock : Pointer to queued spinlock structure
47  * Return: 1 if lock contended, 0 otherwise
48  */
49 static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
50 {
51         return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
52 }
53 /**
54  * queued_spin_trylock - try to acquire the queued spinlock
55  * @lock : Pointer to queued spinlock structure
56  * Return: 1 if lock acquired, 0 if failed
57  */
58 static __always_inline int queued_spin_trylock(struct qspinlock *lock)
59 {
60         u32 val = atomic_read(&lock->val);
61
62         if (unlikely(val))
63                 return 0;
64
65         return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL));
66 }
67
68 extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
69
70 /**
71  * queued_spin_lock - acquire a queued spinlock
72  * @lock: Pointer to queued spinlock structure
73  */
74 static __always_inline void queued_spin_lock(struct qspinlock *lock)
75 {
76         u32 val = 0;
77
78         if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
79                 return;
80
81         queued_spin_lock_slowpath(lock, val);
82 }
83
84 #ifndef queued_spin_unlock
85 /**
86  * queued_spin_unlock - release a queued spinlock
87  * @lock : Pointer to queued spinlock structure
88  */
89 static __always_inline void queued_spin_unlock(struct qspinlock *lock)
90 {
91         /*
92          * unlock() needs release semantics:
93          */
94         smp_store_release(&lock->locked, 0);
95 }
96 #endif
97
98 #ifndef virt_spin_lock
99 static __always_inline bool virt_spin_lock(struct qspinlock *lock)
100 {
101         return false;
102 }
103 #endif
104
105 /*
106  * Remapping spinlock architecture specific functions to the corresponding
107  * queued spinlock functions.
108  */
109 #define arch_spin_is_locked(l)          queued_spin_is_locked(l)
110 #define arch_spin_is_contended(l)       queued_spin_is_contended(l)
111 #define arch_spin_value_unlocked(l)     queued_spin_value_unlocked(l)
112 #define arch_spin_lock(l)               queued_spin_lock(l)
113 #define arch_spin_trylock(l)            queued_spin_trylock(l)
114 #define arch_spin_unlock(l)             queued_spin_unlock(l)
115
116 #endif /* __ASM_GENERIC_QSPINLOCK_H */