X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=doc%2Fexamples%2Fhlist%2Fcds_hlist_del_rcu.c;fp=doc%2Fexamples%2Fhlist%2Fcds_hlist_del_rcu.c;h=1995b215cf24e505daa262d935561aa042f545b0;hb=474190bf1a9025850c14aa67eb88ba9815bb74f4;hp=0000000000000000000000000000000000000000;hpb=d7a0f2fe29db52a5dff734a922ac33654f865836;p=urcu.git diff --git a/doc/examples/hlist/cds_hlist_del_rcu.c b/doc/examples/hlist/cds_hlist_del_rcu.c new file mode 100644 index 0000000..1995b21 --- /dev/null +++ b/doc/examples/hlist/cds_hlist_del_rcu.c @@ -0,0 +1,90 @@ +/* + * Copyright (C) 2013 Mathieu Desnoyers + * + * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED + * OR IMPLIED. ANY USE IS AT YOUR OWN RISK. + * + * Permission is hereby granted to use or copy this program for any + * purpose, provided the above notices are retained on all copies. + * Permission to modify the code and to distribute modified code is + * granted, provided the above notices are retained, and a notice that + * the code was modified is included with the above copyright notice. + * + * This example shows how to remove from a non-circular linked-list + * safely against concurrent RCU traversals. + */ + +#include + +#include /* Userspace RCU flavor */ +#include /* RCU hlist */ +#include /* For CAA_ARRAY_SIZE */ + +/* + * Nodes populated into the list. + */ +struct mynode { + int value; /* Node content */ + struct cds_hlist_node node; /* Linked-list chaining */ + struct rcu_head rcu_head; /* For call_rcu() */ +}; + +static +void free_node_rcu(struct rcu_head *head) +{ + struct mynode *node = caa_container_of(head, struct mynode, rcu_head); + + free(node); +} + +int main(int argc, char **argv) +{ + int values[] = { -5, 42, 36, 24, }; + CDS_HLIST_HEAD(mylist); /* Defines an empty hlist head */ + unsigned int i; + int ret = 0; + struct mynode *node, *n; + + /* + * Adding nodes to the linked-list. Safe against concurrent + * RCU traversals, require mutual exclusion with list updates. + */ + for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { + node = malloc(sizeof(*node)); + if (!node) { + ret = -1; + goto end; + } + node->value = values[i]; + cds_hlist_add_head_rcu(&node->node, &mylist); + } + + /* + * Removing all positive values. Safe against concurrent RCU + * traversals, require mutual exclusion with list updates. + * Notice the "safe" iteration: it is safe against removal of + * nodes as we iterate on the list. + */ + cds_hlist_for_each_entry_safe_2(node, n, &mylist, node) { + if (node->value > 0) { + cds_hlist_del_rcu(&node->node); + /* + * We can only reclaim memory after a grace + * period has passed after cds_hlist_del_rcu(). + */ + call_rcu(&node->rcu_head, free_node_rcu); + } + } + + /* + * Just show the list content. This is _not_ an RCU-safe + * iteration on the list. + */ + printf("mylist content:"); + cds_hlist_for_each_entry_2(node, &mylist, node) { + printf(" %d", node->value); + } + printf("\n"); +end: + return ret; +}