1 /* $NetBSD: refcount.h,v 1.3 2021/12/19 11:52:08 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2020 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #ifndef _LINUX_REFCOUNT_H_ 30 #define _LINUX_REFCOUNT_H_ 31 32 #include <linux/atomic.h> 33 #include <linux/mutex.h> 34 #include <linux/spinlock.h> 35 36 typedef struct refcount refcount_t; 37 38 struct refcount { 39 atomic_t rc_count; 40 }; 41 42 static inline void 43 refcount_set(struct refcount *rc, int n) 44 { 45 atomic_set(&rc->rc_count, n); 46 } 47 48 static inline void 49 refcount_inc(struct refcount *rc) 50 { 51 atomic_inc(&rc->rc_count); 52 } 53 54 static inline int __must_check 55 refcount_inc_not_zero(struct refcount *rc) 56 { 57 unsigned old, new; 58 59 do { 60 old = atomic_read(&rc->rc_count); 61 if (old == 0) 62 break; 63 new = old + 1; 64 } while (atomic_cmpxchg(&rc->rc_count, old, new) != old); 65 66 return old; 67 } 68 69 static inline bool __must_check 70 refcount_dec_and_test(struct refcount *rc) 71 { 72 unsigned old, new; 73 74 do { 75 old = atomic_read(&rc->rc_count); 76 KASSERT(old); 77 new = old - 1; 78 } while (atomic_cmpxchg(&rc->rc_count, old, new) != old); 79 80 return old == 1; 81 } 82 83 static inline bool __must_check 84 refcount_dec_and_lock_irqsave(struct refcount *rc, struct spinlock *lock, 85 unsigned long *flagsp) 86 { 87 88 return atomic_dec_and_lock_irqsave(&rc->rc_count, lock, *flagsp); 89 } 90 91 static inline bool __must_check 92 refcount_dec_and_mutex_lock(struct refcount *rc, struct mutex *lock) 93 { 94 unsigned old, new; 95 96 do { 97 old = atomic_read(&rc->rc_count); 98 KASSERT(old); 99 if (old == 1) { 100 mutex_lock(lock); 101 if (atomic_dec_return(&rc->rc_count) == 0) 102 return true; 103 mutex_unlock(lock); 104 return false; 105 } 106 new = old - 1; 107 } while (atomic_cmpxchg(&rc->rc_count, old, new) != old); 108 109 KASSERT(old != 1); 110 KASSERT(new != 0); 111 return false; 112 } 113 114 #endif /* _LINUX_REFCOUNT_H_ */ 115