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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/export.h>
3#include <linux/lockref.h>
4
5#if USE_CMPXCHG_LOCKREF
6
7/*
8 * Note that the "cmpxchg()" reloads the "old" value for the
9 * failure case.
10 */
11#define CMPXCHG_LOOP(CODE, SUCCESS) do { \
12 int retry = 100; \
13 struct lockref old; \
14 BUILD_BUG_ON(sizeof(old) != 8); \
15 old.lock_count = READ_ONCE(lockref->lock_count); \
16 while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \
17 struct lockref new = old, prev = old; \
18 CODE \
19 old.lock_count = cmpxchg64_relaxed(&lockref->lock_count, \
20 old.lock_count, \
21 new.lock_count); \
22 if (likely(old.lock_count == prev.lock_count)) { \
23 SUCCESS; \
24 } \
25 if (!--retry) \
26 break; \
27 cpu_relax(); \
28 } \
29} while (0)
30
31#else
32
33#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
34
35#endif
36
37/**
38 * lockref_get - Increments reference count unconditionally
39 * @lockref: pointer to lockref structure
40 *
41 * This operation is only valid if you already hold a reference
42 * to the object, so you know the count cannot be zero.
43 */
44void lockref_get(struct lockref *lockref)
45{
46 CMPXCHG_LOOP(
47 new.count++;
48 ,
49 return;
50 );
51
52 spin_lock(&lockref->lock);
53 lockref->count++;
54 spin_unlock(&lockref->lock);
55}
56EXPORT_SYMBOL(lockref_get);
57
58/**
59 * lockref_get_not_zero - Increments count unless the count is 0 or dead
60 * @lockref: pointer to lockref structure
61 * Return: 1 if count updated successfully or 0 if count was zero
62 */
63int lockref_get_not_zero(struct lockref *lockref)
64{
65 int retval;
66
67 CMPXCHG_LOOP(
68 new.count++;
69 if (old.count <= 0)
70 return 0;
71 ,
72 return 1;
73 );
74
75 spin_lock(&lockref->lock);
76 retval = 0;
77 if (lockref->count > 0) {
78 lockref->count++;
79 retval = 1;
80 }
81 spin_unlock(&lockref->lock);
82 return retval;
83}
84EXPORT_SYMBOL(lockref_get_not_zero);
85
86/**
87 * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
88 * @lockref: pointer to lockref structure
89 * Return: 1 if count updated successfully or 0 if count would become zero
90 */
91int lockref_put_not_zero(struct lockref *lockref)
92{
93 int retval;
94
95 CMPXCHG_LOOP(
96 new.count--;
97 if (old.count <= 1)
98 return 0;
99 ,
100 return 1;
101 );
102
103 spin_lock(&lockref->lock);
104 retval = 0;
105 if (lockref->count > 1) {
106 lockref->count--;
107 retval = 1;
108 }
109 spin_unlock(&lockref->lock);
110 return retval;
111}
112EXPORT_SYMBOL(lockref_put_not_zero);
113
114/**
115 * lockref_get_or_lock - Increments count unless the count is 0 or dead
116 * @lockref: pointer to lockref structure
117 * Return: 1 if count updated successfully or 0 if count was zero
118 * and we got the lock instead.
119 */
120int lockref_get_or_lock(struct lockref *lockref)
121{
122 CMPXCHG_LOOP(
123 new.count++;
124 if (old.count <= 0)
125 break;
126 ,
127 return 1;
128 );
129
130 spin_lock(&lockref->lock);
131 if (lockref->count <= 0)
132 return 0;
133 lockref->count++;
134 spin_unlock(&lockref->lock);
135 return 1;
136}
137EXPORT_SYMBOL(lockref_get_or_lock);
138
139/**
140 * lockref_put_return - Decrement reference count if possible
141 * @lockref: pointer to lockref structure
142 *
143 * Decrement the reference count and return the new value.
144 * If the lockref was dead or locked, return an error.
145 */
146int lockref_put_return(struct lockref *lockref)
147{
148 CMPXCHG_LOOP(
149 new.count--;
150 if (old.count <= 0)
151 return -1;
152 ,
153 return new.count;
154 );
155 return -1;
156}
157EXPORT_SYMBOL(lockref_put_return);
158
159/**
160 * lockref_put_or_lock - decrements count unless count <= 1 before decrement
161 * @lockref: pointer to lockref structure
162 * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
163 */
164int lockref_put_or_lock(struct lockref *lockref)
165{
166 CMPXCHG_LOOP(
167 new.count--;
168 if (old.count <= 1)
169 break;
170 ,
171 return 1;
172 );
173
174 spin_lock(&lockref->lock);
175 if (lockref->count <= 1)
176 return 0;
177 lockref->count--;
178 spin_unlock(&lockref->lock);
179 return 1;
180}
181EXPORT_SYMBOL(lockref_put_or_lock);
182
183/**
184 * lockref_mark_dead - mark lockref dead
185 * @lockref: pointer to lockref structure
186 */
187void lockref_mark_dead(struct lockref *lockref)
188{
189 assert_spin_locked(&lockref->lock);
190 lockref->count = -128;
191}
192EXPORT_SYMBOL(lockref_mark_dead);
193
194/**
195 * lockref_get_not_dead - Increments count unless the ref is dead
196 * @lockref: pointer to lockref structure
197 * Return: 1 if count updated successfully or 0 if lockref was dead
198 */
199int lockref_get_not_dead(struct lockref *lockref)
200{
201 int retval;
202
203 CMPXCHG_LOOP(
204 new.count++;
205 if (old.count < 0)
206 return 0;
207 ,
208 return 1;
209 );
210
211 spin_lock(&lockref->lock);
212 retval = 0;
213 if (lockref->count >= 0) {
214 lockref->count++;
215 retval = 1;
216 }
217 spin_unlock(&lockref->lock);
218 return retval;
219}
220EXPORT_SYMBOL(lockref_get_not_dead);
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/export.h>
3#include <linux/lockref.h>
4
5#if USE_CMPXCHG_LOCKREF
6
7/*
8 * Note that the "cmpxchg()" reloads the "old" value for the
9 * failure case.
10 */
11#define CMPXCHG_LOOP(CODE, SUCCESS) do { \
12 int retry = 100; \
13 struct lockref old; \
14 BUILD_BUG_ON(sizeof(old) != 8); \
15 old.lock_count = READ_ONCE(lockref->lock_count); \
16 while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \
17 struct lockref new = old; \
18 CODE \
19 if (likely(try_cmpxchg64_relaxed(&lockref->lock_count, \
20 &old.lock_count, \
21 new.lock_count))) { \
22 SUCCESS; \
23 } \
24 if (!--retry) \
25 break; \
26 } \
27} while (0)
28
29#else
30
31#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
32
33#endif
34
35/**
36 * lockref_get - Increments reference count unconditionally
37 * @lockref: pointer to lockref structure
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 */
42void lockref_get(struct lockref *lockref)
43{
44 CMPXCHG_LOOP(
45 new.count++;
46 ,
47 return;
48 );
49
50 spin_lock(&lockref->lock);
51 lockref->count++;
52 spin_unlock(&lockref->lock);
53}
54EXPORT_SYMBOL(lockref_get);
55
56/**
57 * lockref_get_not_zero - Increments count unless the count is 0 or dead
58 * @lockref: pointer to lockref structure
59 * Return: 1 if count updated successfully or 0 if count was zero
60 */
61int lockref_get_not_zero(struct lockref *lockref)
62{
63 int retval;
64
65 CMPXCHG_LOOP(
66 new.count++;
67 if (old.count <= 0)
68 return 0;
69 ,
70 return 1;
71 );
72
73 spin_lock(&lockref->lock);
74 retval = 0;
75 if (lockref->count > 0) {
76 lockref->count++;
77 retval = 1;
78 }
79 spin_unlock(&lockref->lock);
80 return retval;
81}
82EXPORT_SYMBOL(lockref_get_not_zero);
83
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 */
89int 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}
110EXPORT_SYMBOL(lockref_put_not_zero);
111
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 */
119int 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}
130EXPORT_SYMBOL(lockref_put_return);
131
132/**
133 * lockref_put_or_lock - decrements count unless count <= 1 before decrement
134 * @lockref: pointer to lockref structure
135 * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
136 */
137int lockref_put_or_lock(struct lockref *lockref)
138{
139 CMPXCHG_LOOP(
140 new.count--;
141 if (old.count <= 1)
142 break;
143 ,
144 return 1;
145 );
146
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}
154EXPORT_SYMBOL(lockref_put_or_lock);
155
156/**
157 * lockref_mark_dead - mark lockref dead
158 * @lockref: pointer to lockref structure
159 */
160void lockref_mark_dead(struct lockref *lockref)
161{
162 assert_spin_locked(&lockref->lock);
163 lockref->count = -128;
164}
165EXPORT_SYMBOL(lockref_mark_dead);
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 */
172int lockref_get_not_dead(struct lockref *lockref)
173{
174 int retval;
175
176 CMPXCHG_LOOP(
177 new.count++;
178 if (old.count < 0)
179 return 0;
180 ,
181 return 1;
182 );
183
184 spin_lock(&lockref->lock);
185 retval = 0;
186 if (lockref->count >= 0) {
187 lockref->count++;
188 retval = 1;
189 }
190 spin_unlock(&lockref->lock);
191 return retval;
192}
193EXPORT_SYMBOL(lockref_get_not_dead);