doc/examples/hlist/cds_hlist_for_each_entry_rcu.c

   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  */
  16
  17 #include <stdio.h>
  18
  19 #include <urcu/urcu-memb.h>     /* Userspace RCU flavor */
  20 #include <urcu/rcuhlist.h>      /* RCU hlist */
  21 #include <urcu/compiler.h>      /* For CAA_ARRAY_SIZE */
  22
  23 /*
  24  * Nodes populated into the list.
  25  */
  26 struct mynode {
  27         int value;                      /* Node content */
  28         struct cds_hlist_node node;     /* Linked-list chaining */
  29 };
  30
  31 int main(int argc, char **argv)
  32 {
  33         int values[] = { -5, 42, 36, 24, };
  34         CDS_HLIST_HEAD(mylist);         /* Defines an empty hlist head */
  35         unsigned int i;
  36         int ret = 0;
  37         struct mynode *node;
  38
  39         /*
  40          * Each thread need using RCU read-side need to be explicitly
  41          * registered.
  42          */
  43         urcu_memb_register_thread();
  44
  45         /*
  46          * Adding nodes to the linked-list. Safe against concurrent
  47          * RCU traversals, require mutual exclusion with list updates.
  48          */
  49         for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
  50                 node = malloc(sizeof(*node));
  51                 if (!node) {
  52                         ret = -1;
  53                         goto end;
  54                 }
  55                 node->value = values[i];
  56                 cds_hlist_add_head_rcu(&node->node, &mylist);
  57         }
  58
  59         /*
  60          * RCU-safe iteration on the list.
  61          */
  62         printf("mylist content:");
  63
  64         /*
  65          * Surround the RCU read-side critical section with rcu_read_lock()
  66          * and rcu_read_unlock().
  67          */
  68         urcu_memb_read_lock();
  69
  70         /*
  71          * This traversal can be performed concurrently with RCU
  72          * updates.
  73          */
  74         cds_hlist_for_each_entry_rcu_2(node, &mylist, node) {
  75                 printf(" %d", node->value);
  76         }
  77
  78         urcu_memb_read_unlock();
  79
  80         printf("\n");
  81 end:
  82         urcu_memb_unregister_thread();
  83         return ret;
  84 }