1 // SPDX-License-Identifier: GPL-2.0-only 1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 2 /* 3 * Lock-less NULL terminated single linked lis 3 * Lock-less NULL terminated single linked list 4 * 4 * 5 * The basic atomic operation of this list is 5 * The basic atomic operation of this list is cmpxchg on long. On 6 * architectures that don't have NMI-safe cmpx 6 * architectures that don't have NMI-safe cmpxchg implementation, the 7 * list can NOT be used in NMI handlers. So c 7 * list can NOT be used in NMI handlers. So code that uses the list in 8 * an NMI handler should depend on CONFIG_ARCH 8 * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG. 9 * 9 * 10 * Copyright 2010,2011 Intel Corp. 10 * Copyright 2010,2011 Intel Corp. 11 * Author: Huang Ying <ying.huang@intel.com> 11 * Author: Huang Ying <ying.huang@intel.com> 12 */ 12 */ 13 #include <linux/kernel.h> 13 #include <linux/kernel.h> 14 #include <linux/export.h> 14 #include <linux/export.h> 15 #include <linux/llist.h> 15 #include <linux/llist.h> 16 16 17 17 18 /** 18 /** 19 * llist_add_batch - add several linked entrie 19 * llist_add_batch - add several linked entries in batch 20 * @new_first: first entry in batch to be add 20 * @new_first: first entry in batch to be added 21 * @new_last: last entry in batch to be adde 21 * @new_last: last entry in batch to be added 22 * @head: the head for your lock-less li 22 * @head: the head for your lock-less list 23 * 23 * 24 * Return whether list is empty before adding. 24 * Return whether list is empty before adding. 25 */ 25 */ 26 bool llist_add_batch(struct llist_node *new_fi 26 bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, 27 struct llist_head *head) 27 struct llist_head *head) 28 { 28 { 29 struct llist_node *first = READ_ONCE(h !! 29 struct llist_node *first; 30 30 31 do { 31 do { 32 new_last->next = first; !! 32 new_last->next = first = READ_ONCE(head->first); 33 } while (!try_cmpxchg(&head->first, &f !! 33 } while (cmpxchg(&head->first, first, new_first) != first); 34 34 35 return !first; 35 return !first; 36 } 36 } 37 EXPORT_SYMBOL_GPL(llist_add_batch); 37 EXPORT_SYMBOL_GPL(llist_add_batch); 38 38 39 /** 39 /** 40 * llist_del_first - delete the first entry of 40 * llist_del_first - delete the first entry of lock-less list 41 * @head: the head for your lock-less li 41 * @head: the head for your lock-less list 42 * 42 * 43 * If list is empty, return NULL, otherwise, r 43 * If list is empty, return NULL, otherwise, return the first entry 44 * deleted, this is the newest added one. 44 * deleted, this is the newest added one. 45 * 45 * 46 * Only one llist_del_first user can be used s 46 * Only one llist_del_first user can be used simultaneously with 47 * multiple llist_add users without lock. Bec 47 * multiple llist_add users without lock. Because otherwise 48 * llist_del_first, llist_add, llist_add (or l 48 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add, 49 * llist_add) sequence in another user may cha 49 * llist_add) sequence in another user may change @head->first->next, 50 * but keep @head->first. If multiple consume 50 * but keep @head->first. If multiple consumers are needed, please 51 * use llist_del_all or use lock between consu 51 * use llist_del_all or use lock between consumers. 52 */ 52 */ 53 struct llist_node *llist_del_first(struct llis 53 struct llist_node *llist_del_first(struct llist_head *head) 54 { 54 { 55 struct llist_node *entry, *next; !! 55 struct llist_node *entry, *old_entry, *next; 56 56 57 entry = smp_load_acquire(&head->first) 57 entry = smp_load_acquire(&head->first); 58 do { !! 58 for (;;) { 59 if (entry == NULL) 59 if (entry == NULL) 60 return NULL; 60 return NULL; >> 61 old_entry = entry; 61 next = READ_ONCE(entry->next); 62 next = READ_ONCE(entry->next); 62 } while (!try_cmpxchg(&head->first, &e !! 63 entry = cmpxchg(&head->first, old_entry, next); >> 64 if (entry == old_entry) >> 65 break; >> 66 } 63 67 64 return entry; 68 return entry; 65 } 69 } 66 EXPORT_SYMBOL_GPL(llist_del_first); 70 EXPORT_SYMBOL_GPL(llist_del_first); 67 << 68 /** << 69 * llist_del_first_this - delete given entry o << 70 * @head: the head for your lock-less li << 71 * @this: a list entry. << 72 * << 73 * If head of the list is given entry, delete << 74 * return %false. << 75 * << 76 * Multiple callers can safely call this concu << 77 * llist_add() callers, providing all the call << 78 */ << 79 bool llist_del_first_this(struct llist_head *h << 80 struct llist_node *t << 81 { << 82 struct llist_node *entry, *next; << 83 << 84 /* acquire ensures orderig wrt try_cmp << 85 entry = smp_load_acquire(&head->first) << 86 do { << 87 if (entry != this) << 88 return false; << 89 next = READ_ONCE(entry->next); << 90 } while (!try_cmpxchg(&head->first, &e << 91 << 92 return true; << 93 } << 94 EXPORT_SYMBOL_GPL(llist_del_first_this); << 95 71 96 /** 72 /** 97 * llist_reverse_order - reverse order of a ll 73 * llist_reverse_order - reverse order of a llist chain 98 * @head: first item of the list to be r 74 * @head: first item of the list to be reversed 99 * 75 * 100 * Reverse the order of a chain of llist entri 76 * Reverse the order of a chain of llist entries and return the 101 * new first entry. 77 * new first entry. 102 */ 78 */ 103 struct llist_node *llist_reverse_order(struct 79 struct llist_node *llist_reverse_order(struct llist_node *head) 104 { 80 { 105 struct llist_node *new_head = NULL; 81 struct llist_node *new_head = NULL; 106 82 107 while (head) { 83 while (head) { 108 struct llist_node *tmp = head; 84 struct llist_node *tmp = head; 109 head = head->next; 85 head = head->next; 110 tmp->next = new_head; 86 tmp->next = new_head; 111 new_head = tmp; 87 new_head = tmp; 112 } 88 } 113 89 114 return new_head; 90 return new_head; 115 } 91 } 116 EXPORT_SYMBOL_GPL(llist_reverse_order); 92 EXPORT_SYMBOL_GPL(llist_reverse_order); 117 93
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