X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=doc%2Fexamples%2Frculfqueue%2Fcds_lfq_dequeue.c;fp=doc%2Fexamples%2Frculfqueue%2Fcds_lfq_dequeue.c;h=d1375c8f2c65eea93b72afbb7dd5aa9016b850e8;hb=d4b7140809acb8a9429fa97a4620c96674bd0c3c;hp=0000000000000000000000000000000000000000;hpb=d7818a6fd0c57b576f3bacc67ddd62bc8a78fb05;p=urcu.git diff --git a/doc/examples/rculfqueue/cds_lfq_dequeue.c b/doc/examples/rculfqueue/cds_lfq_dequeue.c new file mode 100644 index 0000000..d1375c8 --- /dev/null +++ b/doc/examples/rculfqueue/cds_lfq_dequeue.c @@ -0,0 +1,115 @@ +/* + * 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 dequeue nodes from a RCU lock-free queue. + * This queue requires using a RCU scheme. + */ + +#include +#include + +#include /* RCU flavor */ +#include /* RCU Lock-free queue */ +#include /* For CAA_ARRAY_SIZE */ + +/* + * Nodes populated into the queue. + */ +struct mynode { + int value; /* Node content */ + struct cds_lfq_node_rcu node; /* Chaining in queue */ + struct rcu_head rcu_head; /* For call_rcu() */ +}; + +static +void free_node(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, }; + struct cds_lfq_queue_rcu myqueue; /* Queue */ + unsigned int i; + int ret = 0; + + /* + * Each thread need using RCU read-side need to be explicitly + * registered. + */ + rcu_register_thread(); + + cds_lfq_init_rcu(&myqueue, call_rcu); + + /* + * Enqueue nodes. + */ + for (i = 0; i < CAA_ARRAY_SIZE(values); i++) { + struct mynode *node; + + node = malloc(sizeof(*node)); + if (!node) { + ret = -1; + goto end; + } + + cds_lfq_node_init_rcu(&node->node); + node->value = values[i]; + /* + * Both enqueue and dequeue need to be called within RCU + * read-side critical section. + */ + rcu_read_lock(); + cds_lfq_enqueue_rcu(&myqueue, &node->node); + rcu_read_unlock(); + } + + /* + * Dequeue each node from the queue. Those will be dequeued from + * the oldest (first enqueued) to the newest (last enqueued). + */ + printf("dequeued content:"); + for (;;) { + struct cds_lfq_node_rcu *qnode; + struct mynode *node; + + /* + * Both enqueue and dequeue need to be called within RCU + * read-side critical section. + */ + rcu_read_lock(); + qnode = cds_lfq_dequeue_rcu(&myqueue); + rcu_read_unlock(); + if (!qnode) { + break; /* Queue is empty. */ + } + /* Getting the container structure from the node */ + node = caa_container_of(qnode, struct mynode, node); + printf(" %d", node->value); + call_rcu(&node->rcu_head, free_node); + } + printf("\n"); + /* + * Release memory used by the queue. + */ + ret = cds_lfq_destroy_rcu(&myqueue); + if (ret) { + printf("Error destroying queue (non-empty)\n"); + } +end: + rcu_unregister_thread(); + return ret; +}