doc/examples/list/cds_list_for_each_entry_rcu.c

   1 // SPDX-FileCopyrightText: 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 //
   3 // SPDX-License-Identifier: MIT
   4
   5 /*
   6  * This example shows how to do a RCU linked list traversal, safely
   7  * against concurrent RCU updates.
   8  */
   9
  10 #include <stdio.h>
  11
  12 #include <urcu/urcu-memb.h>     /* Userspace RCU flavor */
  13 #include <urcu/rculist.h>       /* RCU list */
  14 #include <urcu/compiler.h>      /* For CAA_ARRAY_SIZE */
  15
  16 /*
  17  * Nodes populated into the list.
  18  */
  19 struct mynode {
  20         int value;                      /* Node content */
  21         struct cds_list_head node;      /* Linked-list chaining */
  22 };
  23
  24 int main(void)
  25 {
  26         int values[] = { -5, 42, 36, 24, };
  27         CDS_LIST_HEAD(mylist);          /* Defines an empty list head */
  28         unsigned int i;
  29         int ret = 0;
  30         struct mynode *node;
  31
  32         /*
  33          * Each thread need using RCU read-side need to be explicitly
  34          * registered.
  35          */
  36         urcu_memb_register_thread();
  37
  38         /*
  39          * Adding nodes to the linked-list. Safe against concurrent
  40          * RCU traversals, require mutual exclusion with list updates.
  41          */
  42         for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
  43                 node = malloc(sizeof(*node));
  44                 if (!node) {
  45                         ret = -1;
  46                         goto end;
  47                 }
  48                 node->value = values[i];
  49                 cds_list_add_tail_rcu(&node->node, &mylist);
  50         }
  51
  52         /*
  53          * RCU-safe iteration on the list.
  54          */
  55         printf("mylist content:");
  56
  57         /*
  58          * Surround the RCU read-side critical section with urcu_memb_read_lock()
  59          * and urcu_memb_read_unlock().
  60          */
  61         urcu_memb_read_lock();
  62
  63         /*
  64          * This traversal can be performed concurrently with RCU
  65          * updates.
  66          */
  67         cds_list_for_each_entry_rcu(node, &mylist, node) {
  68                 printf(" %d", node->value);
  69         }
  70
  71         urcu_memb_read_unlock();
  72
  73         printf("\n");
  74 end:
  75         urcu_memb_unregister_thread();
  76         return ret;
  77 }