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                 unsigned cmp = count.fetch_add(0, std::memory_order_seq_cst);
  26                 signal_impl(cmp);
  27         }
  28
  29         unsigned get()
  30         {
  31                 unsigned cmp = count.fetch_or(0x80000000,
  32 std::memory_order_seq_cst);
  33                 return cmp & 0x7FFFFFFF;
  34         }
  35
  36         void wait(unsigned cmp)
  37         {
  38                 unsigned ec = count.load(std::memory_order_seq_cst);
  39                 if (cmp == (ec & 0x7FFFFFFF))
  40                 {
  41                         guard.lock($);
  42                         ec = count.load(std::memory_order_seq_cst);
  43                         if (cmp == (ec & 0x7FFFFFFF))
  44                         {
  45                                 waiters += 1;
  46                                 cv.wait(guard);
  47                         }
  48                         guard.unlock($);
  49                 }
  50         }
  51
  52 private:
  53         std::atomic<unsigned> count;
  54         rl::var<unsigned> waiters;
  55         std::mutex guard;
  56         std::condition_variable cv;
  57
  58         void signal_impl(unsigned cmp)
  59         {
  60                 if (cmp & 0x80000000)
  61                 {
  62                         guard.lock($);
  63                         while (false == count.compare_exchange_weak(cmp,
  64                                 (cmp + 1) & 0x7FFFFFFF, std::memory_order_relaxed));
  65                         unsigned w = waiters($);
  66                         waiters = 0;
  67                         guard.unlock($);
  68                         if (w)
  69                                 cv.notify_all($);
  70                 }
  71         }
  72 };
  73
  74 #endif