spsc-example/spsc-queue.cc

   1 #include <threads.h>
   2 #include <atomic>
   3
   4 //#include "wildcard.h"
   5 using namespace std;
   6
   7 #define acquire memory_order_acquire
   8 #define release memory_order_release
   9 #define relaxed memory_order_relaxed
  10
  11 struct node {
  12         node(int idx) {
  13                 index.store(idx, relaxed);
  14                 next.store(NULL, relaxed);
  15         }
  16         atomic<node*> next;/*@ \label{line:spscNodeNext} @*/
  17         atomic<int> index;/*@ \label{line:spscNodeIndex} @*/
  18 };/*@ \label{line:spscNodeEnd} @*/
  19
  20 class spsc_queue {/*@ \label{line:spscBegin} @*/
  21         node *head, *tail;
  22         public:
  23         spsc_queue() {
  24                 head = tail = new node(-1);
  25         }
  26         void enqueue(int idx) {
  27                 node* n = new node(idx);
  28                 tail->next.store(n, relaxed); // Should be release/*@ \label{line:spscRelease} @*/
  29                 tail = n;
  30         }
  31         bool dequeue(int *idx) {
  32                 node *tmp = head;
  33                 node *n = tmp->next.load(relaxed); // Should be acquire/*@ \label{line:spscAcquire} @*/
  34                 if (NULL == n) return false;
  35                 head = n;
  36                 *idx = n->index.load(relaxed);
  37                 delete (tmp);
  38                 return true;
  39         }
  40 };/*@ \label{line:spscEnd} @*/
  41
  42 spsc_queue *q;/*@ \label{line:testcaseBegin} @*/
  43 atomic_int arr[2];
  44 void thrd1() { // Thread 1/*@ \label{line:thrd1} @*/
  45         arr[1].store(47, relaxed);/*@ \label{line:spscRelaxedStore} @*/
  46         q->enqueue(1);
  47 }
  48 void thrd2() { // Thread 2/*@ \label{line:thrd2} @*/
  49         int idx;
  50         if (q->dequeue(&idx))
  51                 arr[idx].load(relaxed);/*@ \label{line:spscRelaxedLoad} @*/
  52 }/*@ \label{line:testcaseEnd} @*/
  53
  54 int user_main(int argc, char **argv)
  55 {
  56         thrd_t A, B;
  57         q = new spsc_queue;
  58         thrd_create(&A, (thrd_start_t)&thrd1, NULL);
  59         thrd_create(&B, (thrd_start_t)&thrd2, NULL);
  60         thrd_join(A);
  61         thrd_join(B);
  62
  63         //delete q;
  64
  65         return 0;
  66 }