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 #include <linux/atomic.h>
15
16 #ifndef queued_spin_is_locked
17 /**
18 * queued_spin_is_locked - is the spinlock locked?
19 * @lock: Pointer to queued spinlock structure
20 * Return: 1 if it is locked, 0 otherwise
21 */
queued_spin_is_locked(struct qspinlock * lock)22 static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
23 {
24 /*
25 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
26 * isn't immediately observable.
27 */
28 return atomic_read(&lock->val);
29 }
30 #endif
31
32 /**
33 * queued_spin_value_unlocked - is the spinlock structure unlocked?
34 * @lock: queued spinlock structure
35 * Return: 1 if it is unlocked, 0 otherwise
36 *
37 * N.B. Whenever there are tasks waiting for the lock, it is considered
38 * locked wrt the lockref code to avoid lock stealing by the lockref
39 * code and change things underneath the lock. This also allows some
40 * optimizations to be applied without conflict with lockref.
41 */
queued_spin_value_unlocked(struct qspinlock lock)42 static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
43 {
44 return !atomic_read(&lock.val);
45 }
46
47 /**
48 * queued_spin_is_contended - check if the lock is contended
49 * @lock : Pointer to queued spinlock structure
50 * Return: 1 if lock contended, 0 otherwise
51 */
queued_spin_is_contended(struct qspinlock * lock)52 static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
53 {
54 return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
55 }
56 /**
57 * queued_spin_trylock - try to acquire the queued spinlock
58 * @lock : Pointer to queued spinlock structure
59 * Return: 1 if lock acquired, 0 if failed
60 */
queued_spin_trylock(struct qspinlock * lock)61 static __always_inline int queued_spin_trylock(struct qspinlock *lock)
62 {
63 u32 val = atomic_read(&lock->val);
64
65 if (unlikely(val))
66 return 0;
67
68 return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL));
69 }
70
71 extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
72
73 #ifndef queued_spin_lock
74 /**
75 * queued_spin_lock - acquire a queued spinlock
76 * @lock: Pointer to queued spinlock structure
77 */
queued_spin_lock(struct qspinlock * lock)78 static __always_inline void queued_spin_lock(struct qspinlock *lock)
79 {
80 u32 val = 0;
81
82 if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
83 return;
84
85 queued_spin_lock_slowpath(lock, val);
86 }
87 #endif
88
89 #ifndef queued_spin_unlock
90 /**
91 * queued_spin_unlock - release a queued spinlock
92 * @lock : Pointer to queued spinlock structure
93 */
queued_spin_unlock(struct qspinlock * lock)94 static __always_inline void queued_spin_unlock(struct qspinlock *lock)
95 {
96 /*
97 * unlock() needs release semantics:
98 */
99 smp_store_release(&lock->locked, 0);
100 }
101 #endif
102
103 #ifndef virt_spin_lock
virt_spin_lock(struct qspinlock * lock)104 static __always_inline bool virt_spin_lock(struct qspinlock *lock)
105 {
106 return false;
107 }
108 #endif
109
110 /*
111 * Remapping spinlock architecture specific functions to the corresponding
112 * queued spinlock functions.
113 */
114 #define arch_spin_is_locked(l) queued_spin_is_locked(l)
115 #define arch_spin_is_contended(l) queued_spin_is_contended(l)
116 #define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
117 #define arch_spin_lock(l) queued_spin_lock(l)
118 #define arch_spin_trylock(l) queued_spin_trylock(l)
119 #define arch_spin_unlock(l) queued_spin_unlock(l)
120
121 #endif /* __ASM_GENERIC_QSPINLOCK_H */
122
