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a33fda35 WL |
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. | |
64d816cb | 15 | * (C) Copyright 2015 Hewlett-Packard Enterprise Development LP |
a33fda35 | 16 | * |
64d816cb | 17 | * Authors: Waiman Long <waiman.long@hpe.com> |
a33fda35 WL |
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_is_locked - is the spinlock locked? | |
26 | * @lock: Pointer to queued spinlock structure | |
27 | * Return: 1 if it is locked, 0 otherwise | |
28 | */ | |
2c610022 | 29 | #ifndef queued_spin_is_locked |
a33fda35 WL |
30 | static __always_inline int queued_spin_is_locked(struct qspinlock *lock) |
31 | { | |
54cf809b | 32 | /* |
2c610022 PZ |
33 | * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL |
34 | * isn't immediately observable. | |
54cf809b | 35 | */ |
2c610022 | 36 | return atomic_read(&lock->val); |
a33fda35 | 37 | } |
2c610022 | 38 | #endif |
a33fda35 WL |
39 | |
40 | /** | |
41 | * queued_spin_value_unlocked - is the spinlock structure unlocked? | |
42 | * @lock: queued spinlock structure | |
43 | * Return: 1 if it is unlocked, 0 otherwise | |
44 | * | |
45 | * N.B. Whenever there are tasks waiting for the lock, it is considered | |
46 | * locked wrt the lockref code to avoid lock stealing by the lockref | |
47 | * code and change things underneath the lock. This also allows some | |
48 | * optimizations to be applied without conflict with lockref. | |
49 | */ | |
50 | static __always_inline int queued_spin_value_unlocked(struct qspinlock lock) | |
51 | { | |
52 | return !atomic_read(&lock.val); | |
53 | } | |
54 | ||
55 | /** | |
56 | * queued_spin_is_contended - check if the lock is contended | |
57 | * @lock : Pointer to queued spinlock structure | |
58 | * Return: 1 if lock contended, 0 otherwise | |
59 | */ | |
60 | static __always_inline int queued_spin_is_contended(struct qspinlock *lock) | |
61 | { | |
62 | return atomic_read(&lock->val) & ~_Q_LOCKED_MASK; | |
63 | } | |
64 | /** | |
65 | * queued_spin_trylock - try to acquire the queued spinlock | |
66 | * @lock : Pointer to queued spinlock structure | |
67 | * Return: 1 if lock acquired, 0 if failed | |
68 | */ | |
69 | static __always_inline int queued_spin_trylock(struct qspinlock *lock) | |
70 | { | |
71 | if (!atomic_read(&lock->val) && | |
64d816cb | 72 | (atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL) == 0)) |
a33fda35 WL |
73 | return 1; |
74 | return 0; | |
75 | } | |
76 | ||
77 | extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val); | |
78 | ||
79 | /** | |
80 | * queued_spin_lock - acquire a queued spinlock | |
81 | * @lock: Pointer to queued spinlock structure | |
82 | */ | |
83 | static __always_inline void queued_spin_lock(struct qspinlock *lock) | |
84 | { | |
85 | u32 val; | |
86 | ||
64d816cb | 87 | val = atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL); |
a33fda35 WL |
88 | if (likely(val == 0)) |
89 | return; | |
90 | queued_spin_lock_slowpath(lock, val); | |
91 | } | |
92 | ||
93 | #ifndef queued_spin_unlock | |
94 | /** | |
95 | * queued_spin_unlock - release a queued spinlock | |
96 | * @lock : Pointer to queued spinlock structure | |
97 | */ | |
98 | static __always_inline void queued_spin_unlock(struct qspinlock *lock) | |
99 | { | |
100 | /* | |
ca50e426 | 101 | * unlock() needs release semantics: |
a33fda35 | 102 | */ |
ca50e426 | 103 | (void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val); |
a33fda35 WL |
104 | } |
105 | #endif | |
106 | ||
43b3f028 PZ |
107 | #ifndef virt_spin_lock |
108 | static __always_inline bool virt_spin_lock(struct qspinlock *lock) | |
2aa79af6 PZI |
109 | { |
110 | return false; | |
111 | } | |
112 | #endif | |
113 | ||
a33fda35 WL |
114 | /* |
115 | * Remapping spinlock architecture specific functions to the corresponding | |
116 | * queued spinlock functions. | |
117 | */ | |
118 | #define arch_spin_is_locked(l) queued_spin_is_locked(l) | |
119 | #define arch_spin_is_contended(l) queued_spin_is_contended(l) | |
120 | #define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l) | |
121 | #define arch_spin_lock(l) queued_spin_lock(l) | |
122 | #define arch_spin_trylock(l) queued_spin_trylock(l) | |
123 | #define arch_spin_unlock(l) queued_spin_unlock(l) | |
a33fda35 WL |
124 | |
125 | #endif /* __ASM_GENERIC_QSPINLOCK_H */ |