1 /* 2 * Lock-less NULL terminated single linked list 3 * 4 * The basic atomic operation of this list is cmpxchg on long. On 5 * architectures that don't have NMI-safe cmpxchg implementation, the 6 * list can NOT be used in NMI handler. So code uses the list in NMI 7 * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG. 8 * 9 * Copyright 2010,2011 Intel Corp. 10 * Author: Huang Ying <ying.huang@intel.com> 11 * 12 * This program is free software; you can redistribute it and/or 13 * modify it under the terms of the GNU General Public License version 14 * 2 as published by the Free Software Foundation; 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, write to the Free Software 23 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 24 */ 25 #include <linux/kernel.h> 26 #include <linux/module.h> 27 #include <linux/interrupt.h> 28 #include <linux/llist.h> 29 30 #include <asm/system.h> 31 32 /** 33 * llist_add - add a new entry 34 * @new: new entry to be added 35 * @head: the head for your lock-less list 36 */ 37 void llist_add(struct llist_node *new, struct llist_head *head) 38 { 39 struct llist_node *entry, *old_entry; 40 41 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG 42 BUG_ON(in_nmi()); 43 #endif 44 45 entry = head->first; 46 do { 47 old_entry = entry; 48 new->next = entry; 49 cpu_relax(); 50 } while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry); 51 } 52 EXPORT_SYMBOL_GPL(llist_add); 53 54 /** 55 * llist_add_batch - add several linked entries in batch 56 * @new_first: first entry in batch to be added 57 * @new_last: last entry in batch to be added 58 * @head: the head for your lock-less list 59 */ 60 void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, 61 struct llist_head *head) 62 { 63 struct llist_node *entry, *old_entry; 64 65 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG 66 BUG_ON(in_nmi()); 67 #endif 68 69 entry = head->first; 70 do { 71 old_entry = entry; 72 new_last->next = entry; 73 cpu_relax(); 74 } while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry); 75 } 76 EXPORT_SYMBOL_GPL(llist_add_batch); 77 78 /** 79 * llist_del_first - delete the first entry of lock-less list 80 * @head: the head for your lock-less list 81 * 82 * If list is empty, return NULL, otherwise, return the first entry 83 * deleted, this is the newest added one. 84 * 85 * Only one llist_del_first user can be used simultaneously with 86 * multiple llist_add users without lock. Because otherwise 87 * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add, 88 * llist_add) sequence in another user may change @head->first->next, 89 * but keep @head->first. If multiple consumers are needed, please 90 * use llist_del_all or use lock between consumers. 91 */ 92 struct llist_node *llist_del_first(struct llist_head *head) 93 { 94 struct llist_node *entry, *old_entry, *next; 95 96 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG 97 BUG_ON(in_nmi()); 98 #endif 99 100 entry = head->first; 101 do { 102 if (entry == NULL) 103 return NULL; 104 old_entry = entry; 105 next = entry->next; 106 cpu_relax(); 107 } while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry); 108 109 return entry; 110 } 111 EXPORT_SYMBOL_GPL(llist_del_first); 112 113 /** 114 * llist_del_all - delete all entries from lock-less list 115 * @head: the head of lock-less list to delete all entries 116 * 117 * If list is empty, return NULL, otherwise, delete all entries and 118 * return the pointer to the first entry. The order of entries 119 * deleted is from the newest to the oldest added one. 120 */ 121 struct llist_node *llist_del_all(struct llist_head *head) 122 { 123 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG 124 BUG_ON(in_nmi()); 125 #endif 126 127 return xchg(&head->first, NULL); 128 } 129 EXPORT_SYMBOL_GPL(llist_del_all); 130