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156 lines · 3.5 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2016 Facebook
3 */
4#include "percpu_freelist.h"
5
6int 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_res_spin_lock_init(&head->lock);
18 head->first = NULL;
19 }
20 raw_res_spin_lock_init(&s->extralist.lock);
21 s->extralist.first = NULL;
22 return 0;
23}
24
25void pcpu_freelist_destroy(struct pcpu_freelist *s)
26{
27 free_percpu(s->freelist);
28}
29
30static 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
37static inline bool ___pcpu_freelist_push(struct pcpu_freelist_head *head,
38 struct pcpu_freelist_node *node)
39{
40 if (raw_res_spin_lock(&head->lock))
41 return false;
42 pcpu_freelist_push_node(head, node);
43 raw_res_spin_unlock(&head->lock);
44 return true;
45}
46
47void __pcpu_freelist_push(struct pcpu_freelist *s,
48 struct pcpu_freelist_node *node)
49{
50 struct pcpu_freelist_head *head;
51 int cpu, this_cpu;
52
53 if (___pcpu_freelist_push(this_cpu_ptr(s->freelist), node))
54 return;
55
56 this_cpu = raw_smp_processor_id();
57 while (true) {
58 for_each_cpu_wrap(cpu, cpu_possible_mask, this_cpu) {
59 if (cpu == this_cpu)
60 continue;
61
62 head = per_cpu_ptr(s->freelist, cpu);
63 if (___pcpu_freelist_push(head, node))
64 return;
65 }
66
67 /*
68 * Push cannot fail. Use the extra list when none of the
69 * per-CPU freelists can accept the node.
70 */
71 if (___pcpu_freelist_push(&s->extralist, node))
72 return;
73 }
74}
75
76void pcpu_freelist_push(struct pcpu_freelist *s,
77 struct pcpu_freelist_node *node)
78{
79 unsigned long flags;
80
81 local_irq_save(flags);
82 __pcpu_freelist_push(s, node);
83 local_irq_restore(flags);
84}
85
86void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size,
87 u32 nr_elems)
88{
89 struct pcpu_freelist_head *head;
90 unsigned int cpu, cpu_idx, i, j, n, m;
91
92 n = nr_elems / num_possible_cpus();
93 m = nr_elems % num_possible_cpus();
94
95 cpu_idx = 0;
96 for_each_possible_cpu(cpu) {
97 head = per_cpu_ptr(s->freelist, cpu);
98 j = n + (cpu_idx < m ? 1 : 0);
99 for (i = 0; i < j; i++) {
100 /* No locking required as this is not visible yet. */
101 pcpu_freelist_push_node(head, buf);
102 buf += elem_size;
103 }
104 cpu_idx++;
105 }
106}
107
108static struct pcpu_freelist_node *___pcpu_freelist_pop(struct pcpu_freelist *s)
109{
110 struct pcpu_freelist_node *node = NULL;
111 struct pcpu_freelist_head *head;
112 int cpu;
113
114 for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) {
115 head = per_cpu_ptr(s->freelist, cpu);
116 if (!READ_ONCE(head->first))
117 continue;
118 if (raw_res_spin_lock(&head->lock))
119 continue;
120 node = head->first;
121 if (node) {
122 WRITE_ONCE(head->first, node->next);
123 raw_res_spin_unlock(&head->lock);
124 return node;
125 }
126 raw_res_spin_unlock(&head->lock);
127 }
128
129 /* Per-CPU lists are empty or unavailable, try the extra list. */
130 head = &s->extralist;
131 if (!READ_ONCE(head->first))
132 return NULL;
133 if (raw_res_spin_lock(&head->lock))
134 return NULL;
135 node = head->first;
136 if (node)
137 WRITE_ONCE(head->first, node->next);
138 raw_res_spin_unlock(&head->lock);
139 return node;
140}
141
142struct pcpu_freelist_node *__pcpu_freelist_pop(struct pcpu_freelist *s)
143{
144 return ___pcpu_freelist_pop(s);
145}
146
147struct pcpu_freelist_node *pcpu_freelist_pop(struct pcpu_freelist *s)
148{
149 struct pcpu_freelist_node *ret;
150 unsigned long flags;
151
152 local_irq_save(flags);
153 ret = __pcpu_freelist_pop(s);
154 local_irq_restore(flags);
155 return ret;
156}