1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2016 Facebook
3 */
4 #include "percpu_freelist.h"
5
6 int pcpu_freelist_init(struct pcpu_freelist *s)
7 {
8 int cpu;
9
10 s->freelist = alloc_percpu(struct pcpu_freelist_head);
11 if (!s->freelist)
12 return -ENOMEM;
13
14 for_each_possible_cpu(cpu) {
15 struct pcpu_freelist_head *head = per_cpu_ptr(s->freelist, cpu);
16
17 raw_spin_lock_init(&head->lock);
18 head->first = NULL;
19 }
20 raw_spin_lock_init(&s->extralist.lock);
21 s->extralist.first = NULL;
22 return 0;
23 }
24
25 void pcpu_freelist_destroy(struct pcpu_freelist *s)
26 {
27 free_percpu(s->freelist);
28 }
29
30 static inline void pcpu_freelist_push_node(struct pcpu_freelist_head *head,
31 struct pcpu_freelist_node *node)
32 {
33 node->next = head->first;
34 WRITE_ONCE(head->first, node);
35 }
36
37 static inline void ___pcpu_freelist_push(struct pcpu_freelist_head *head,
38 struct pcpu_freelist_node *node)
39 {
40 raw_spin_lock(&head->lock);
41 pcpu_freelist_push_node(head, node);
42 raw_spin_unlock(&head->lock);
43 }
44
45 static inline bool pcpu_freelist_try_push_extra(struct pcpu_freelist *s,
46 struct pcpu_freelist_node *node)
47 {
48 if (!raw_spin_trylock(&s->extralist.lock))
49 return false;
50
51 pcpu_freelist_push_node(&s->extralist, node);
52 raw_spin_unlock(&s->extralist.lock);
53 return true;
54 }
55
56 static inline void ___pcpu_freelist_push_nmi(struct pcpu_freelist *s,
57 struct pcpu_freelist_node *node)
58 {
59 int cpu, orig_cpu;
60
61 orig_cpu = raw_smp_processor_id();
62 while (1) {
63 for_each_cpu_wrap(cpu, cpu_possible_mask, orig_cpu) {
64 struct pcpu_freelist_head *head;
65
66 head = per_cpu_ptr(s->freelist, cpu);
67 if (raw_spin_trylock(&head->lock)) {
68 pcpu_freelist_push_node(head, node);
69 raw_spin_unlock(&head->lock);
70 return;
71 }
72 }
73
74 /* cannot lock any per cpu lock, try extralist */
75 if (pcpu_freelist_try_push_extra(s, node))
76 return;
77 }
78 }
79
80 void __pcpu_freelist_push(struct pcpu_freelist *s,
81 struct pcpu_freelist_node *node)
82 {
83 if (in_nmi())
84 ___pcpu_freelist_push_nmi(s, node);
85 else
86 ___pcpu_freelist_push(this_cpu_ptr(s->freelist), node);
87 }
88
89 void pcpu_freelist_push(struct pcpu_freelist *s,
90 struct pcpu_freelist_node *node)
91 {
92 unsigned long flags;
93
94 local_irq_save(flags);
95 __pcpu_freelist_push(s, node);
96 local_irq_restore(flags);
97 }
98
99 void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size,
100 u32 nr_elems)
101 {
102 struct pcpu_freelist_head *head;
103 unsigned int cpu, cpu_idx, i, j, n, m;
104
105 n = nr_elems / num_possible_cpus();
106 m = nr_elems % num_possible_cpus();
107
108 cpu_idx = 0;
109 for_each_possible_cpu(cpu) {
110 head = per_cpu_ptr(s->freelist, cpu);
111 j = n + (cpu_idx < m ? 1 : 0);
112 for (i = 0; i < j; i++) {
113 /* No locking required as this is not visible yet. */
114 pcpu_freelist_push_node(head, buf);
115 buf += elem_size;
116 }
117 cpu_idx++;
118 }
119 }
120
121 static struct pcpu_freelist_node *___pcpu_freelist_pop(struct pcpu_freelist *s)
122 {
123 struct pcpu_freelist_head *head;
124 struct pcpu_freelist_node *node;
125 int cpu;
126
127 for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) {
128 head = per_cpu_ptr(s->freelist, cpu);
129 if (!READ_ONCE(head->first))
130 continue;
131 raw_spin_lock(&head->lock);
132 node = head->first;
133 if (node) {
134 WRITE_ONCE(head->first, node->next);
135 raw_spin_unlock(&head->lock);
136 return node;
137 }
138 raw_spin_unlock(&head->lock);
139 }
140
141 /* per cpu lists are all empty, try extralist */
142 if (!READ_ONCE(s->extralist.first))
143 return NULL;
144 raw_spin_lock(&s->extralist.lock);
145 node = s->extralist.first;
146 if (node)
147 WRITE_ONCE(s->extralist.first, node->next);
148 raw_spin_unlock(&s->extralist.lock);
149 return node;
150 }
151
152 static struct pcpu_freelist_node *
153 ___pcpu_freelist_pop_nmi(struct pcpu_freelist *s)
154 {
155 struct pcpu_freelist_head *head;
156 struct pcpu_freelist_node *node;
157 int cpu;
158
159 for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) {
160 head = per_cpu_ptr(s->freelist, cpu);
161 if (!READ_ONCE(head->first))
162 continue;
163 if (raw_spin_trylock(&head->lock)) {
164 node = head->first;
165 if (node) {
166 WRITE_ONCE(head->first, node->next);
167 raw_spin_unlock(&head->lock);
168 return node;
169 }
170 raw_spin_unlock(&head->lock);
171 }
172 }
173
174 /* cannot pop from per cpu lists, try extralist */
175 if (!READ_ONCE(s->extralist.first) || !raw_spin_trylock(&s->extralist.lock))
176 return NULL;
177 node = s->extralist.first;
178 if (node)
179 WRITE_ONCE(s->extralist.first, node->next);
180 raw_spin_unlock(&s->extralist.lock);
181 return node;
182 }
183
184 struct pcpu_freelist_node *__pcpu_freelist_pop(struct pcpu_freelist *s)
185 {
186 if (in_nmi())
187 return ___pcpu_freelist_pop_nmi(s);
188 return ___pcpu_freelist_pop(s);
189 }
190
191 struct pcpu_freelist_node *pcpu_freelist_pop(struct pcpu_freelist *s)
192 {
193 struct pcpu_freelist_node *ret;
194 unsigned long flags;
195
196 local_irq_save(flags);
197 ret = __pcpu_freelist_pop(s);
198 local_irq_restore(flags);
199 return ret;
200 }
201
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