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