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Waiman Longa33fda32015-04-24 14:56:30 -04001/*
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.
Waiman Long64d816c2015-11-09 19:09:21 -050015 * (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
Waiman Longa33fda32015-04-24 14:56:30 -040016 *
Waiman Long64d816c2015-11-09 19:09:21 -050017 * Authors: Waiman Long <waiman.long@hpe.com>
Waiman Longa33fda32015-04-24 14:56:30 -040018 */
19#ifndef __ASM_GENERIC_QSPINLOCK_H
20#define __ASM_GENERIC_QSPINLOCK_H
21
22#include <asm-generic/qspinlock_types.h>
23
24/**
Peter Zijlstra2c610022016-06-08 10:19:51 +020025 * 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/**
Waiman Longa33fda32015-04-24 14:56:30 -040036 * 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 */
Peter Zijlstra2c610022016-06-08 10:19:51 +020040#ifndef queued_spin_is_locked
Waiman Longa33fda32015-04-24 14:56:30 -040041static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
42{
Peter Zijlstra54cf8092016-05-20 18:04:36 +020043 /*
Peter Zijlstra2c610022016-06-08 10:19:51 +020044 * See queued_spin_unlock_wait().
Peter Zijlstra54cf8092016-05-20 18:04:36 +020045 *
Peter Zijlstra2c610022016-06-08 10:19:51 +020046 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
47 * isn't immediately observable.
Peter Zijlstra54cf8092016-05-20 18:04:36 +020048 */
Peter Zijlstra2c610022016-06-08 10:19:51 +020049 return atomic_read(&lock->val);
Waiman Longa33fda32015-04-24 14:56:30 -040050}
Peter Zijlstra2c610022016-06-08 10:19:51 +020051#endif
Waiman Longa33fda32015-04-24 14:56:30 -040052
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) &&
Waiman Long64d816c2015-11-09 19:09:21 -050085 (atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL) == 0))
Waiman Longa33fda32015-04-24 14:56:30 -040086 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
Waiman Long64d816c2015-11-09 19:09:21 -0500100 val = atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL);
Waiman Longa33fda32015-04-24 14:56:30 -0400101 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 /*
Pan Xinhuica50e422016-06-03 16:38:14 +0800114 * unlock() needs release semantics:
Waiman Longa33fda32015-04-24 14:56:30 -0400115 */
Pan Xinhuica50e422016-06-03 16:38:14 +0800116 (void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val);
Waiman Longa33fda32015-04-24 14:56:30 -0400117}
118#endif
119
Peter Zijlstra43b3f022015-09-04 17:25:23 +0200120#ifndef virt_spin_lock
121static __always_inline bool virt_spin_lock(struct qspinlock *lock)
Peter Zijlstra (Intel)2aa79af2015-04-24 14:56:36 -0400122{
123 return false;
124}
125#endif
126
Waiman Longa33fda32015-04-24 14:56:30 -0400127/*
Waiman Longa33fda32015-04-24 14:56:30 -0400128 * 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 */