projects / userspace-rcu.git / blame
| Commit | Line | Data |
|---|---|---|
| 453629a9 MD |
1 | #ifndef _URCU_REF_H |
| 2 | #define _URCU_REF_H | |
| 3 | ||
| 4 | /* | |
| 5 | * Userspace RCU - Reference counting | |
| 6 | * | |
| 7 | * Copyright (C) 2009 Novell Inc. | |
| 8 | * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
| 9 | * | |
| 10 | * Author: Jan Blunck <jblunck@suse.de> | |
| 11 | * | |
| 12 | * This program is free software; you can redistribute it and/or modify it | |
| 13 | * under the terms of the GNU Lesser General Public License version 2.1 as | |
| 14 | * published by the Free Software Foundation. | |
| 15 | */ | |
| 16 | ||
| cd21955a | 17 | #include <stdbool.h> |
| 7ce99d02 MD |
18 | #include <limits.h> |
| 19 | #include <stdlib.h> | |
| 01477510 | 20 | #include <urcu/assert.h> |
| a2e7bf9c | 21 | #include <urcu/uatomic.h> |
| 453629a9 MD |
22 | |
| 23 | struct urcu_ref { | |
| 24 | long refcount; /* ATOMIC */ | |
| 25 | }; | |
| 26 | ||
| 27 | static inline void urcu_ref_set(struct urcu_ref *ref, long val) | |
| 28 | { | |
| 29 | uatomic_set(&ref->refcount, val); | |
| 30 | } | |
| 31 | ||
| 32 | static inline void urcu_ref_init(struct urcu_ref *ref) | |
| 33 | { | |
| 34 | urcu_ref_set(ref, 1); | |
| 35 | } | |
| 36 | ||
| 8b4b5a1a MD |
37 | static inline bool __attribute__((warn_unused_result)) |
| 38 | urcu_ref_get_safe(struct urcu_ref *ref) | |
| 453629a9 | 39 | { |
| 7ce99d02 MD |
40 | long old, _new, res; |
| 41 | ||
| 42 | old = uatomic_read(&ref->refcount); | |
| 43 | for (;;) { | |
| 44 | if (old == LONG_MAX) { | |
| 8b4b5a1a | 45 | return false; /* Failure. */ |
| 7ce99d02 MD |
46 | } |
| 47 | _new = old + 1; | |
| 48 | res = uatomic_cmpxchg(&ref->refcount, old, _new); | |
| 49 | if (res == old) { | |
| 8b4b5a1a | 50 | return true; /* Success. */ |
| 7ce99d02 MD |
51 | } |
| 52 | old = res; | |
| 53 | } | |
| 453629a9 MD |
54 | } |
| 55 | ||
| 8b4b5a1a MD |
56 | static inline void urcu_ref_get(struct urcu_ref *ref) |
| 57 | { | |
| 58 | if (!urcu_ref_get_safe(ref)) | |
| 59 | abort(); | |
| 60 | } | |
| 61 | ||
| 453629a9 MD |
62 | static inline void urcu_ref_put(struct urcu_ref *ref, |
| 63 | void (*release)(struct urcu_ref *)) | |
| 64 | { | |
| bf27322d | 65 | long res = uatomic_sub_return(&ref->refcount, 1); |
| 01477510 | 66 | urcu_posix_assert(res >= 0); |
| bf27322d | 67 | if (res == 0) |
| 453629a9 MD |
68 | release(ref); |
| 69 | } | |
| 70 | ||
| cd21955a MD |
71 | /* |
| 72 | * urcu_ref_get_unless_zero | |
| 73 | * | |
| 74 | * Allows getting a reference atomically if the reference count is not | |
| 75 | * zero. Returns true if the reference is taken, false otherwise. This | |
| 76 | * needs to be used in conjunction with another synchronization | |
| 77 | * technique (e.g. RCU or mutex) to ensure existence of the reference | |
| 7ce99d02 MD |
78 | * count. False is also returned in case incrementing the refcount would |
| 79 | * result in an overflow. | |
| cd21955a MD |
80 | */ |
| 81 | static inline bool urcu_ref_get_unless_zero(struct urcu_ref *ref) | |
| 82 | { | |
| 83 | long old, _new, res; | |
| 84 | ||
| 85 | old = uatomic_read(&ref->refcount); | |
| 86 | for (;;) { | |
| 7ce99d02 | 87 | if (old == 0 || old == LONG_MAX) |
| cd21955a MD |
88 | return false; /* Failure. */ |
| 89 | _new = old + 1; | |
| 90 | res = uatomic_cmpxchg(&ref->refcount, old, _new); | |
| 91 | if (res == old) { | |
| 92 | return true; /* Success. */ | |
| 93 | } | |
| 94 | old = res; | |
| 95 | } | |
| 96 | } | |
| 97 | ||
| 453629a9 | 98 | #endif /* _URCU_REF_H */ |