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