| 1 | /* |
| 2 | * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 3 | * |
| 4 | * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED |
| 5 | * OR IMPLIED. ANY USE IS AT YOUR OWN RISK. |
| 6 | * |
| 7 | * Permission is hereby granted to use or copy this program for any |
| 8 | * purpose, provided the above notices are retained on all copies. |
| 9 | * Permission to modify the code and to distribute modified code is |
| 10 | * granted, provided the above notices are retained, and a notice that |
| 11 | * the code was modified is included with the above copyright notice. |
| 12 | * |
| 13 | * This example shows how to do a non-circular RCU linked list |
| 14 | * traversal, safely against concurrent RCU updates. |
| 15 | * cds_hlist_for_each_rcu() iterates on struct cds_hlist_node, and thus, |
| 16 | * either caa_container_of() or cds_hlist_entry() are needed to access |
| 17 | * the container structure. |
| 18 | */ |
| 19 | |
| 20 | #include <stdio.h> |
| 21 | |
| 22 | #include <urcu/urcu-memb.h> /* Userspace RCU flavor */ |
| 23 | #include <urcu/rcuhlist.h> /* RCU hlist */ |
| 24 | #include <urcu/compiler.h> /* For CAA_ARRAY_SIZE */ |
| 25 | |
| 26 | /* |
| 27 | * Nodes populated into the list. |
| 28 | */ |
| 29 | struct mynode { |
| 30 | int value; /* Node content */ |
| 31 | struct cds_hlist_node node; /* Linked-list chaining */ |
| 32 | }; |
| 33 | |
| 34 | int main(int argc, char **argv) |
| 35 | { |
| 36 | int values[] = { -5, 42, 36, 24, }; |
| 37 | CDS_HLIST_HEAD(mylist); /* Defines an empty hlist head */ |
| 38 | unsigned int i; |
| 39 | int ret = 0; |
| 40 | struct cds_hlist_node *pos; |
| 41 | |
| 42 | /* |
| 43 | * Each thread need using RCU read-side need to be explicitly |
| 44 | * registered. |
| 45 | */ |
| 46 | urcu_memb_register_thread(); |
| 47 | |
| 48 | /* |
| 49 | * Adding nodes to the linked-list. Safe against concurrent |
| 50 | * RCU traversals, require mutual exclusion with list updates. |
| 51 | */ |
| 52 | for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { |
| 53 | struct mynode *node; |
| 54 | |
| 55 | node = malloc(sizeof(*node)); |
| 56 | if (!node) { |
| 57 | ret = -1; |
| 58 | goto end; |
| 59 | } |
| 60 | node->value = values[i]; |
| 61 | cds_hlist_add_head_rcu(&node->node, &mylist); |
| 62 | } |
| 63 | |
| 64 | /* |
| 65 | * RCU-safe iteration on the list. |
| 66 | */ |
| 67 | printf("mylist content:"); |
| 68 | |
| 69 | /* |
| 70 | * Surround the RCU read-side critical section with rcu_read_lock() |
| 71 | * and rcu_read_unlock(). |
| 72 | */ |
| 73 | urcu_memb_read_lock(); |
| 74 | |
| 75 | /* |
| 76 | * This traversal can be performed concurrently with RCU |
| 77 | * updates. |
| 78 | */ |
| 79 | cds_hlist_for_each_rcu(pos, &mylist) { |
| 80 | struct mynode *node = cds_hlist_entry(pos, struct mynode, node); |
| 81 | |
| 82 | printf(" %d", node->value); |
| 83 | } |
| 84 | |
| 85 | urcu_memb_read_unlock(); |
| 86 | |
| 87 | printf("\n"); |
| 88 | end: |
| 89 | urcu_memb_unregister_thread(); |
| 90 | return ret; |
| 91 | } |