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