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 /** 17 * queued_spin_is_locked - is the spinlock locked? 18 * @lock: Pointer to queued spinlock structure 19 * Return: 1 if it is locked, 0 otherwise 20 */ 21 static __always_inline int queued_spin_is_locked(struct qspinlock *lock) 22 { 23 /* 24 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL 25 * isn't immediately observable. 26 */ 27 return atomic_read(&lock->val); 28 } 29 30 /** 31 * queued_spin_value_unlocked - is the spinlock structure unlocked? 32 * @lock: queued spinlock structure 33 * Return: 1 if it is unlocked, 0 otherwise 34 * 35 * N.B. Whenever there are tasks waiting for the lock, it is considered 36 * locked wrt the lockref code to avoid lock stealing by the lockref 37 * code and change things underneath the lock. This also allows some 38 * optimizations to be applied without conflict with lockref. 39 */ 40 static __always_inline int queued_spin_value_unlocked(struct qspinlock lock) 41 { 42 return !atomic_read(&lock.val); 43 } 44 45 /** 46 * queued_spin_is_contended - check if the lock is contended 47 * @lock : Pointer to queued spinlock structure 48 * Return: 1 if lock contended, 0 otherwise 49 */ 50 static __always_inline int queued_spin_is_contended(struct qspinlock *lock) 51 { 52 return atomic_read(&lock->val) & ~_Q_LOCKED_MASK; 53 } 54 /** 55 * queued_spin_trylock - try to acquire the queued spinlock 56 * @lock : Pointer to queued spinlock structure 57 * Return: 1 if lock acquired, 0 if failed 58 */ 59 static __always_inline int queued_spin_trylock(struct qspinlock *lock) 60 { 61 u32 val = atomic_read(&lock->val); 62 63 if (unlikely(val)) 64 return 0; 65 66 return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)); 67 } 68 69 extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val); 70 71 /** 72 * queued_spin_lock - acquire a queued spinlock 73 * @lock: Pointer to queued spinlock structure 74 */ 75 static __always_inline void queued_spin_lock(struct qspinlock *lock) 76 { 77 u32 val = 0; 78 79 if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL))) 80 return; 81 82 queued_spin_lock_slowpath(lock, val); 83 } 84 85 #ifndef queued_spin_unlock 86 /** 87 * queued_spin_unlock - release a queued spinlock 88 * @lock : Pointer to queued spinlock structure 89 */ 90 static __always_inline void queued_spin_unlock(struct qspinlock *lock) 91 { 92 /* 93 * unlock() needs release semantics: 94 */ 95 smp_store_release(&lock->locked, 0); 96 } 97 #endif 98 99 #ifndef virt_spin_lock 100 static __always_inline bool virt_spin_lock(struct qspinlock *lock) 101 { 102 return false; 103 } 104 #endif 105 106 /* 107 * Remapping spinlock architecture specific functions to the corresponding 108 * queued spinlock functions. 109 */ 110 #define arch_spin_is_locked(l) queued_spin_is_locked(l) 111 #define arch_spin_is_contended(l) queued_spin_is_contended(l) 112 #define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l) 113 #define arch_spin_lock(l) queued_spin_lock(l) 114 #define arch_spin_trylock(l) queued_spin_trylock(l) 115 #define arch_spin_unlock(l) queued_spin_unlock(l) 116 117 #endif /* __ASM_GENERIC_QSPINLOCK_H */ 118