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_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
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 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
45static 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
56static 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
80void __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
89void 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
99void 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
121static 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
152static 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
184struct 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
191struct 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