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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; \ | |
f2f09a4c | 26 | cpu_relax(); \ |
bc08b449 LT |
27 | } \ |
28 | } while (0) | |
29 | ||
30 | #else | |
31 | ||
32 | #define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0) | |
33 | ||
34 | #endif | |
35 | ||
2f4f12e5 LT |
36 | /** |
37 | * lockref_get - Increments reference count unconditionally | |
44a0cf92 | 38 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
39 | * |
40 | * This operation is only valid if you already hold a reference | |
41 | * to the object, so you know the count cannot be zero. | |
42 | */ | |
43 | void lockref_get(struct lockref *lockref) | |
44 | { | |
bc08b449 LT |
45 | CMPXCHG_LOOP( |
46 | new.count++; | |
47 | , | |
48 | return; | |
49 | ); | |
50 | ||
2f4f12e5 LT |
51 | spin_lock(&lockref->lock); |
52 | lockref->count++; | |
53 | spin_unlock(&lockref->lock); | |
54 | } | |
55 | EXPORT_SYMBOL(lockref_get); | |
56 | ||
57 | /** | |
360f5479 | 58 | * lockref_get_not_zero - Increments count unless the count is 0 or dead |
44a0cf92 | 59 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
60 | * Return: 1 if count updated successfully or 0 if count was zero |
61 | */ | |
62 | int lockref_get_not_zero(struct lockref *lockref) | |
63 | { | |
bc08b449 LT |
64 | int retval; |
65 | ||
66 | CMPXCHG_LOOP( | |
67 | new.count++; | |
360f5479 | 68 | if (old.count <= 0) |
bc08b449 LT |
69 | return 0; |
70 | , | |
71 | return 1; | |
72 | ); | |
2f4f12e5 LT |
73 | |
74 | spin_lock(&lockref->lock); | |
bc08b449 | 75 | retval = 0; |
360f5479 | 76 | if (lockref->count > 0) { |
2f4f12e5 LT |
77 | lockref->count++; |
78 | retval = 1; | |
79 | } | |
80 | spin_unlock(&lockref->lock); | |
81 | return retval; | |
82 | } | |
83 | EXPORT_SYMBOL(lockref_get_not_zero); | |
84 | ||
450b1f6f AG |
85 | /** |
86 | * lockref_put_not_zero - Decrements count unless count <= 1 before decrement | |
87 | * @lockref: pointer to lockref structure | |
88 | * Return: 1 if count updated successfully or 0 if count would become zero | |
89 | */ | |
90 | int lockref_put_not_zero(struct lockref *lockref) | |
91 | { | |
92 | int retval; | |
93 | ||
94 | CMPXCHG_LOOP( | |
95 | new.count--; | |
96 | if (old.count <= 1) | |
97 | return 0; | |
98 | , | |
99 | return 1; | |
100 | ); | |
101 | ||
102 | spin_lock(&lockref->lock); | |
103 | retval = 0; | |
104 | if (lockref->count > 1) { | |
105 | lockref->count--; | |
106 | retval = 1; | |
107 | } | |
108 | spin_unlock(&lockref->lock); | |
109 | return retval; | |
110 | } | |
111 | EXPORT_SYMBOL(lockref_put_not_zero); | |
112 | ||
360f5479 LT |
113 | /** |
114 | * lockref_put_return - Decrement reference count if possible | |
115 | * @lockref: pointer to lockref structure | |
116 | * | |
117 | * Decrement the reference count and return the new value. | |
118 | * If the lockref was dead or locked, return an error. | |
119 | */ | |
120 | int lockref_put_return(struct lockref *lockref) | |
121 | { | |
122 | CMPXCHG_LOOP( | |
123 | new.count--; | |
124 | if (old.count <= 0) | |
125 | return -1; | |
126 | , | |
127 | return new.count; | |
128 | ); | |
129 | return -1; | |
130 | } | |
131 | EXPORT_SYMBOL(lockref_put_return); | |
132 | ||
2f4f12e5 LT |
133 | /** |
134 | * lockref_put_or_lock - decrements count unless count <= 1 before decrement | |
44a0cf92 | 135 | * @lockref: pointer to lockref structure |
2f4f12e5 LT |
136 | * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken |
137 | */ | |
138 | int lockref_put_or_lock(struct lockref *lockref) | |
139 | { | |
bc08b449 LT |
140 | CMPXCHG_LOOP( |
141 | new.count--; | |
142 | if (old.count <= 1) | |
143 | break; | |
144 | , | |
145 | return 1; | |
146 | ); | |
147 | ||
2f4f12e5 LT |
148 | spin_lock(&lockref->lock); |
149 | if (lockref->count <= 1) | |
150 | return 0; | |
151 | lockref->count--; | |
152 | spin_unlock(&lockref->lock); | |
153 | return 1; | |
154 | } | |
155 | EXPORT_SYMBOL(lockref_put_or_lock); | |
e7d33bb5 LT |
156 | |
157 | /** | |
158 | * lockref_mark_dead - mark lockref dead | |
159 | * @lockref: pointer to lockref structure | |
160 | */ | |
161 | void lockref_mark_dead(struct lockref *lockref) | |
162 | { | |
163 | assert_spin_locked(&lockref->lock); | |
164 | lockref->count = -128; | |
165 | } | |
e66cf161 | 166 | EXPORT_SYMBOL(lockref_mark_dead); |
e7d33bb5 LT |
167 | |
168 | /** | |
169 | * lockref_get_not_dead - Increments count unless the ref is dead | |
170 | * @lockref: pointer to lockref structure | |
171 | * Return: 1 if count updated successfully or 0 if lockref was dead | |
172 | */ | |
173 | int lockref_get_not_dead(struct lockref *lockref) | |
174 | { | |
175 | int retval; | |
176 | ||
177 | CMPXCHG_LOOP( | |
178 | new.count++; | |
360f5479 | 179 | if (old.count < 0) |
e7d33bb5 LT |
180 | return 0; |
181 | , | |
182 | return 1; | |
183 | ); | |
184 | ||
185 | spin_lock(&lockref->lock); | |
186 | retval = 0; | |
360f5479 | 187 | if (lockref->count >= 0) { |
e7d33bb5 LT |
188 | lockref->count++; |
189 | retval = 1; | |
190 | } | |
191 | spin_unlock(&lockref->lock); | |
192 | return retval; | |
193 | } | |
194 | EXPORT_SYMBOL(lockref_get_not_dead); |