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