X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=doc%2Fexamples%2Furcu-flavors%2Fbp.c;fp=doc%2Fexamples%2Furcu-flavors%2Fbp.c;h=64978fcef2f8f305e3c4f72078f99b415d98fc25;hb=9b4bf32b5757c99226eb78bea03f911536f2e9fc;hp=0000000000000000000000000000000000000000;hpb=0485c1bf2c39ea457d80369816c378ba02c6695b;p=urcu.git diff --git a/doc/examples/urcu-flavors/bp.c b/doc/examples/urcu-flavors/bp.c new file mode 100644 index 0000000..64978fc --- /dev/null +++ b/doc/examples/urcu-flavors/bp.c @@ -0,0 +1,115 @@ +/* + * Copyright (C) 2013 Mathieu Desnoyers + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include +#include +#include +#include +#include + +#include /* Bulletproof RCU flavor */ +#include /* List example */ +#include /* For CAA_ARRAY_SIZE */ + +/* + * Example showing how to use the Bulletproof Userspace RCU flavor. + * + * This is a mock-up example where updates and RCU traversals are + * performed by the same thread to keep things simple on purpose. + */ + +static CDS_LIST_HEAD(mylist); + +struct mynode { + uint64_t value; + struct cds_list_head node; /* linked-list chaining */ + struct rcu_head rcu_head; /* for call_rcu() */ +}; + +static +int add_node(uint64_t v) +{ + struct mynode *node; + + node = calloc(sizeof(*node), 1); + if (!node) + return -1; + node->value = v; + cds_list_add_rcu(&node->node, &mylist); + return 0; +} + +int main(int argc, char **argv) +{ + uint64_t values[] = { 42, 36, 24, }; + unsigned int i; + int ret; + struct mynode *node, *n; + + /* + * Notice that with the bulletproof flavor, there is no need to + * register/unregister RCU reader threads. + */ + + /* + * 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++) { + ret = add_node(values[i]); + if (ret) + goto end; + } + + /* + * We need to explicitly mark RCU read-side critical sections + * with rcu_read_lock() and rcu_read_unlock(). They can be + * nested. Those are no-ops for the QSBR flavor. + */ + rcu_read_lock(); + + /* + * RCU traversal of the linked list. + */ + cds_list_for_each_entry_rcu(node, &mylist, node) { + printf("Value: %" PRIu64 "\n", node->value); + } + rcu_read_unlock(); + + /* + * Removing nodes from linked list. Safe against concurrent RCU + * traversals, require mutual exclusion with list updates. + */ + cds_list_for_each_entry_safe(node, n, &mylist, node) { + cds_list_del_rcu(&node->node); + + /* + * Using synchronize_rcu() directly for synchronization + * so we keep a minimal impact on the system by not + * spawning any call_rcu() thread. It is slower though, + * since there is no batching. + */ + synchronize_rcu(); + free(node); + } + + sleep(1); + +end: + return ret; +}