Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
2f4f12e5 LT |
2 | #include <linux/export.h> |
3 | #include <linux/lockref.h> | |
4 | ||
57f4257e | 5 | #if USE_CMPXCHG_LOCKREF |
bc08b449 LT |
6 | |
7 | /* | |
8 | * Note that the "cmpxchg()" reloads the "old" value for the | |
9 | * failure case. | |
10 | */ | |
11 | #define CMPXCHG_LOOP(CODE, SUCCESS) do { \ | |
893a7d32 | 12 | int retry = 100; \ |
bc08b449 LT |
13 | struct lockref old; \ |
14 | BUILD_BUG_ON(sizeof(old) != 8); \ | |
4d3199e4 | 15 | old.lock_count = READ_ONCE(lockref->lock_count); \ |
bc08b449 | 16 | while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \ |
3378323b | 17 | struct lockref new = old; \ |
bc08b449 | 18 | CODE \ |
3378323b UB |
19 | if (likely(try_cmpxchg64_relaxed(&lockref->lock_count, \ |
20 | &old.lock_count, \ | |
21 | new.lock_count))) { \ | |
bc08b449 LT |
22 | SUCCESS; \ |
23 | } \ | |
893a7d32 JG |
24 | if (!--retry) \ |
25 | break; \ | |
bc08b449 LT |
26 | } \ |
27 | } while (0) | |
28 | ||
29 | #else | |
30 | ||
31 | #define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0) | |
32 | ||
33 | #endif | |
34 | ||
2f4f12e5 LT |
35 | /** |
36 | * lockref_get - Increments reference count unconditionally | |
44a0cf92 | 37 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
38 | * |
39 | * This operation is only valid if you already hold a reference | |
40 | * to the object, so you know the count cannot be zero. | |
41 | */ | |
42 | void lockref_get(struct lockref *lockref) | |
43 | { | |
bc08b449 LT |
44 | CMPXCHG_LOOP( |
45 | new.count++; | |
46 | , | |
47 | return; | |
48 | ); | |
49 | ||
2f4f12e5 LT |
50 | spin_lock(&lockref->lock); |
51 | lockref->count++; | |
52 | spin_unlock(&lockref->lock); | |
53 | } | |
54 | EXPORT_SYMBOL(lockref_get); | |
55 | ||
56 | /** | |
360f5479 | 57 | * lockref_get_not_zero - Increments count unless the count is 0 or dead |
44a0cf92 | 58 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
59 | * Return: 1 if count updated successfully or 0 if count was zero |
60 | */ | |
61 | int lockref_get_not_zero(struct lockref *lockref) | |
62 | { | |
bc08b449 LT |
63 | int retval; |
64 | ||
65 | CMPXCHG_LOOP( | |
66 | new.count++; | |
360f5479 | 67 | if (old.count <= 0) |
bc08b449 LT |
68 | return 0; |
69 | , | |
70 | return 1; | |
71 | ); | |
2f4f12e5 LT |
72 | |
73 | spin_lock(&lockref->lock); | |
bc08b449 | 74 | retval = 0; |
360f5479 | 75 | if (lockref->count > 0) { |
2f4f12e5 LT |
76 | lockref->count++; |
77 | retval = 1; | |
78 | } | |
79 | spin_unlock(&lockref->lock); | |
80 | return retval; | |
81 | } | |
82 | EXPORT_SYMBOL(lockref_get_not_zero); | |
83 | ||
450b1f6f AG |
84 | /** |
85 | * lockref_put_not_zero - Decrements count unless count <= 1 before decrement | |
86 | * @lockref: pointer to lockref structure | |
87 | * Return: 1 if count updated successfully or 0 if count would become zero | |
88 | */ | |
89 | int lockref_put_not_zero(struct lockref *lockref) | |
90 | { | |
91 | int retval; | |
92 | ||
93 | CMPXCHG_LOOP( | |
94 | new.count--; | |
95 | if (old.count <= 1) | |
96 | return 0; | |
97 | , | |
98 | return 1; | |
99 | ); | |
100 | ||
101 | spin_lock(&lockref->lock); | |
102 | retval = 0; | |
103 | if (lockref->count > 1) { | |
104 | lockref->count--; | |
105 | retval = 1; | |
106 | } | |
107 | spin_unlock(&lockref->lock); | |
108 | return retval; | |
109 | } | |
110 | EXPORT_SYMBOL(lockref_put_not_zero); | |
111 | ||
360f5479 LT |
112 | /** |
113 | * lockref_put_return - Decrement reference count if possible | |
114 | * @lockref: pointer to lockref structure | |
115 | * | |
116 | * Decrement the reference count and return the new value. | |
117 | * If the lockref was dead or locked, return an error. | |
118 | */ | |
119 | int lockref_put_return(struct lockref *lockref) | |
120 | { | |
121 | CMPXCHG_LOOP( | |
122 | new.count--; | |
123 | if (old.count <= 0) | |
124 | return -1; | |
125 | , | |
126 | return new.count; | |
127 | ); | |
128 | return -1; | |
129 | } | |
130 | EXPORT_SYMBOL(lockref_put_return); | |
131 | ||
2f4f12e5 LT |
132 | /** |
133 | * lockref_put_or_lock - decrements count unless count <= 1 before decrement | |
44a0cf92 | 134 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
135 | * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken |
136 | */ | |
137 | int lockref_put_or_lock(struct lockref *lockref) | |
138 | { | |
bc08b449 LT |
139 | CMPXCHG_LOOP( |
140 | new.count--; | |
141 | if (old.count <= 1) | |
142 | break; | |
143 | , | |
144 | return 1; | |
145 | ); | |
146 | ||
2f4f12e5 LT |
147 | spin_lock(&lockref->lock); |
148 | if (lockref->count <= 1) | |
149 | return 0; | |
150 | lockref->count--; | |
151 | spin_unlock(&lockref->lock); | |
152 | return 1; | |
153 | } | |
154 | EXPORT_SYMBOL(lockref_put_or_lock); | |
e7d33bb5 LT |
155 | |
156 | /** | |
157 | * lockref_mark_dead - mark lockref dead | |
158 | * @lockref: pointer to lockref structure | |
159 | */ | |
160 | void lockref_mark_dead(struct lockref *lockref) | |
161 | { | |
162 | assert_spin_locked(&lockref->lock); | |
163 | lockref->count = -128; | |
164 | } | |
e66cf161 | 165 | EXPORT_SYMBOL(lockref_mark_dead); |
e7d33bb5 LT |
166 | |
167 | /** | |
168 | * lockref_get_not_dead - Increments count unless the ref is dead | |
169 | * @lockref: pointer to lockref structure | |
170 | * Return: 1 if count updated successfully or 0 if lockref was dead | |
171 | */ | |
172 | int lockref_get_not_dead(struct lockref *lockref) | |
173 | { | |
174 | int retval; | |
175 | ||
176 | CMPXCHG_LOOP( | |
177 | new.count++; | |
360f5479 | 178 | if (old.count < 0) |
e7d33bb5 LT |
179 | return 0; |
180 | , | |
181 | return 1; | |
182 | ); | |
183 | ||
184 | spin_lock(&lockref->lock); | |
185 | retval = 0; | |
360f5479 | 186 | if (lockref->count >= 0) { |
e7d33bb5 LT |
187 | lockref->count++; |
188 | retval = 1; | |
189 | } | |
190 | spin_unlock(&lockref->lock); | |
191 | return retval; | |
192 | } | |
193 | EXPORT_SYMBOL(lockref_get_not_dead); |