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1/*
2 * Queued spinlock
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
15 * (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
16 *
17 * Authors: Waiman Long <waiman.long@hpe.com>
18 */
19#ifndef __ASM_GENERIC_QSPINLOCK_H
20#define __ASM_GENERIC_QSPINLOCK_H
21
22#include <asm-generic/qspinlock_types.h>
23
24/**
25 * queued_spin_unlock_wait - wait until the _current_ lock holder releases the lock
26 * @lock : Pointer to queued spinlock structure
27 *
28 * There is a very slight possibility of live-lock if the lockers keep coming
29 * and the waiter is just unfortunate enough to not see any unlock state.
30 */
31#ifndef queued_spin_unlock_wait
32extern void queued_spin_unlock_wait(struct qspinlock *lock);
33#endif
34
35/**
36 * queued_spin_is_locked - is the spinlock locked?
37 * @lock: Pointer to queued spinlock structure
38 * Return: 1 if it is locked, 0 otherwise
39 */
40#ifndef queued_spin_is_locked
41static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
42{
43 /*
44 * See queued_spin_unlock_wait().
45 *
46 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
47 * isn't immediately observable.
48 */
49 return atomic_read(&lock->val);
50}
51#endif
52
53/**
54 * queued_spin_value_unlocked - is the spinlock structure unlocked?
55 * @lock: queued spinlock structure
56 * Return: 1 if it is unlocked, 0 otherwise
57 *
58 * N.B. Whenever there are tasks waiting for the lock, it is considered
59 * locked wrt the lockref code to avoid lock stealing by the lockref
60 * code and change things underneath the lock. This also allows some
61 * optimizations to be applied without conflict with lockref.
62 */
63static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
64{
65 return !atomic_read(&lock.val);
66}
67
68/**
69 * queued_spin_is_contended - check if the lock is contended
70 * @lock : Pointer to queued spinlock structure
71 * Return: 1 if lock contended, 0 otherwise
72 */
73static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
74{
75 return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
76}
77/**
78 * queued_spin_trylock - try to acquire the queued spinlock
79 * @lock : Pointer to queued spinlock structure
80 * Return: 1 if lock acquired, 0 if failed
81 */
82static __always_inline int queued_spin_trylock(struct qspinlock *lock)
83{
84 if (!atomic_read(&lock->val) &&
85 (atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL) == 0))
86 return 1;
87 return 0;
88}
89
90extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
91
92/**
93 * queued_spin_lock - acquire a queued spinlock
94 * @lock: Pointer to queued spinlock structure
95 */
96static __always_inline void queued_spin_lock(struct qspinlock *lock)
97{
98 u32 val;
99
100 val = atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL);
101 if (likely(val == 0))
102 return;
103 queued_spin_lock_slowpath(lock, val);
104}
105
106#ifndef queued_spin_unlock
107/**
108 * queued_spin_unlock - release a queued spinlock
109 * @lock : Pointer to queued spinlock structure
110 */
111static __always_inline void queued_spin_unlock(struct qspinlock *lock)
112{
113 /*
114 * unlock() needs release semantics:
115 */
116 (void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val);
117}
118#endif
119
120#ifndef virt_spin_lock
121static __always_inline bool virt_spin_lock(struct qspinlock *lock)
122{
123 return false;
124}
125#endif
126
127/*
128 * Remapping spinlock architecture specific functions to the corresponding
129 * queued spinlock functions.
130 */
131#define arch_spin_is_locked(l) queued_spin_is_locked(l)
132#define arch_spin_is_contended(l) queued_spin_is_contended(l)
133#define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
134#define arch_spin_lock(l) queued_spin_lock(l)
135#define arch_spin_trylock(l) queued_spin_trylock(l)
136#define arch_spin_unlock(l) queued_spin_unlock(l)
137#define arch_spin_lock_flags(l, f) queued_spin_lock(l)
138#define arch_spin_unlock_wait(l) queued_spin_unlock_wait(l)
139
140#endif /* __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#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 */
22static __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 */
42static __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 */
52static __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 */
61static __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
71extern 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 */
78static __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 */
94static __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
104static __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 */