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.
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.
14 * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
16 * Authors: Waiman Long <waiman.long@hp.com>
18 #ifndef __ASM_GENERIC_QSPINLOCK_H
19 #define __ASM_GENERIC_QSPINLOCK_H
21 #include <asm-generic/qspinlock_types.h>
24 * queued_spin_unlock_wait - wait until the _current_ lock holder releases the lock
25 * @lock : Pointer to queued spinlock structure
27 * There is a very slight possibility of live-lock if the lockers keep coming
28 * and the waiter is just unfortunate enough to not see any unlock state.
30 #ifndef queued_spin_unlock_wait
31 extern void queued_spin_unlock_wait(struct qspinlock *lock);
35 * queued_spin_is_locked - is the spinlock locked?
36 * @lock: Pointer to queued spinlock structure
37 * Return: 1 if it is locked, 0 otherwise
39 #ifndef queued_spin_is_locked
40 static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
43 * See queued_spin_unlock_wait().
45 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
46 * isn't immediately observable.
48 return atomic_read(&lock->val);
53 * queued_spin_value_unlocked - is the spinlock structure unlocked?
54 * @lock: queued spinlock structure
55 * Return: 1 if it is unlocked, 0 otherwise
57 * N.B. Whenever there are tasks waiting for the lock, it is considered
58 * locked wrt the lockref code to avoid lock stealing by the lockref
59 * code and change things underneath the lock. This also allows some
60 * optimizations to be applied without conflict with lockref.
62 static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
64 return !atomic_read(&lock.val);
68 * queued_spin_is_contended - check if the lock is contended
69 * @lock : Pointer to queued spinlock structure
70 * Return: 1 if lock contended, 0 otherwise
72 static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
74 return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
77 * queued_spin_trylock - try to acquire the queued spinlock
78 * @lock : Pointer to queued spinlock structure
79 * Return: 1 if lock acquired, 0 if failed
81 static __always_inline int queued_spin_trylock(struct qspinlock *lock)
83 if (!atomic_read(&lock->val) &&
84 (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) == 0))
89 extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
92 * queued_spin_lock - acquire a queued spinlock
93 * @lock: Pointer to queued spinlock structure
95 static __always_inline void queued_spin_lock(struct qspinlock *lock)
99 val = atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL);
100 if (likely(val == 0))
102 queued_spin_lock_slowpath(lock, val);
105 #ifndef queued_spin_unlock
107 * queued_spin_unlock - release a queued spinlock
108 * @lock : Pointer to queued spinlock structure
110 static __always_inline void queued_spin_unlock(struct qspinlock *lock)
113 * smp_mb__before_atomic() in order to guarantee release semantics
115 smp_mb__before_atomic_dec();
116 atomic_sub(_Q_LOCKED_VAL, &lock->val);
120 #ifndef virt_spin_lock
121 static __always_inline bool virt_spin_lock(struct qspinlock *lock)
130 #define __ARCH_SPIN_LOCK_UNLOCKED { ATOMIC_INIT(0) }
133 * Remapping spinlock architecture specific functions to the corresponding
134 * queued spinlock functions.
136 #define arch_spin_is_locked(l) queued_spin_is_locked(l)
137 #define arch_spin_is_contended(l) queued_spin_is_contended(l)
138 #define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
139 #define arch_spin_lock(l) queued_spin_lock(l)
140 #define arch_spin_trylock(l) queued_spin_trylock(l)
141 #define arch_spin_unlock(l) queued_spin_unlock(l)
142 #define arch_spin_lock_flags(l, f) queued_spin_lock(l)
143 #define arch_spin_unlock_wait(l) queued_spin_unlock_wait(l)
145 #endif /* __ASM_GENERIC_QSPINLOCK_H */