spsc-queue-scfence/queue.h

   1 #include <unrelacy.h>
   2 #include <atomic>
   3
   4 #include "eventcount.h"
   5 #include "wildcard.h"
   6
   7 class spsc_queue
   8 {
   9 public:
  10         spsc_queue()
  11         {
  12                 node* n = new node (-1);
  13                 head = n;
  14                 tail = n;
  15         }
  16
  17         ~spsc_queue()
  18         {
  19                 RL_ASSERT(head == tail);
  20                 delete ((node*)head($));
  21         }
  22
  23         void enqueue(int data)
  24         {
  25                 node* n = new node (data);
  26                 head($)->next.store(n, wildcard(6));
  27                 head = n;
  28                 ec.signal_relaxed();
  29         }
  30
  31         int dequeue()
  32         {
  33                 int data = try_dequeue();
  34                 while (0 == data)
  35                 {
  36                         int cmp = ec.get();
  37                         data = try_dequeue();
  38                         if (data)
  39                                 break;
  40                         ec.wait(cmp);
  41                         thrd_yield();
  42                         data = try_dequeue();
  43                         if (data)
  44                                 break;
  45                 }
  46                 return data;
  47         }
  48
  49 private:
  50         struct node
  51         {
  52                 std::atomic<node*> next;
  53                 std::atomic<int> data;
  54
  55                 node(int d)
  56                 {
  57                         data.store(d, memory_order_normal);
  58                         next = 0;
  59                 }
  60         };
  61
  62         rl::var<node*> head;
  63         rl::var<node*> tail;
  64
  65         eventcount ec;
  66
  67         int try_dequeue()
  68         {
  69                 node* t = tail($);
  70                 node* n = t->next.load(wildcard(7));
  71                 if (0 == n)
  72                         return 0;
  73                 int data = n->data.load(memory_order_normal);
  74                 delete (t);
  75                 tail = n;
  76                 return data;
  77         }
  78 };