benchmark/spsc-bugfix/eventcount.h

   1 #ifndef _EVENTCOUNT_H
   2 #define _EVENTCOUNT_H
   3
   4 //#include <unrelacy.h>
   5 #include <atomic>
   6 #include <mutex>
   7 #include <condition_variable>
   8
   9 class eventcount
  10 {
  11 public:
  12         eventcount() : waiters(0)
  13         {
  14                 count = 0;
  15         }
  16
  17         void signal_relaxed()
  18         {
  19                 unsigned cmp = count.load(std::memory_order_relaxed);
  20                 signal_impl(cmp);
  21         }
  22
  23         void signal()
  24         {
  25                 // We might be able to use release here because it basically only needs
  26                 // to synchronize with the get()
  27                 unsigned cmp = count.fetch_add(0, std::memory_order_seq_cst);
  28                 signal_impl(cmp);
  29         }
  30
  31         unsigned get()
  32         {
  33                 unsigned cmp = count.fetch_or(0x80000000,
  34 std::memory_order_seq_cst);
  35                 return cmp & 0x7FFFFFFF;
  36         }
  37
  38         void wait(unsigned cmp)
  39         {
  40                 unsigned ec = count.load(std::memory_order_seq_cst);
  41                 if (cmp == (ec & 0x7FFFFFFF))
  42                 {
  43                         guard.lock($);
  44                         ec = count.load(std::memory_order_seq_cst);
  45                         if (cmp == (ec & 0x7FFFFFFF))
  46                         {
  47                                 waiters += 1;
  48                                 cv.wait(guard);
  49                         }
  50                         guard.unlock($);
  51                 }
  52         }
  53
  54 private:
  55         std::atomic<unsigned> count;
  56         rl::var<unsigned> waiters;
  57         std::mutex guard;
  58         std::condition_variable cv;
  59
  60         void signal_impl(unsigned cmp)
  61         {
  62                 if (cmp & 0x80000000)
  63                 {
  64                         guard.lock($);
  65                         while (false == count.compare_exchange_weak(cmp,
  66                                 (cmp + 1) & 0x7FFFFFFF, std::memory_order_relaxed));
  67                         unsigned w = waiters($);
  68                         waiters = 0;
  69                         guard.unlock($);
  70                         if (w)
  71                                 cv.notify_all($);
  72                 }
  73         }
  74 };
  75
  76 #endif