spsc-queue: add new benchmark

[model-checker-benchmarks.git] / spsc-queue / eventcount.h

diff --git a/spsc-queue/eventcount.h b/spsc-queue/eventcount.h
new file mode 100644 (file)
index 0000000..226603e
--- /dev/null
+++ b/spsc-queue/eventcount.h
@@ -0,0 +1,64 @@
+class eventcount
+{
+public:
+       eventcount()
+               : count(0)
+               , waiters(0)
+       {}
+
+       void signal_relaxed()
+       {
+               unsigned cmp = count($).load(std::memory_order_relaxed);
+               signal_impl(cmp);
+       }
+
+       void signal()
+       {
+               unsigned cmp = count($).fetch_add(0, std::memory_order_seq_cst);
+               signal_impl(cmp);
+       }
+
+       unsigned get()
+       {
+               unsigned cmp = count($).fetch_or(0x80000000,
+std::memory_order_seq_cst);
+               return cmp & 0x7FFFFFFF;
+       }
+
+       void wait(unsigned cmp)
+       {
+               unsigned ec = count($).load(std::memory_order_seq_cst);
+               if (cmp == (ec & 0x7FFFFFFF))
+               {
+                       guard.lock($);
+                       ec = count($).load(std::memory_order_seq_cst);
+                       if (cmp == (ec & 0x7FFFFFFF))
+                       {
+                               waiters($) += 1;
+                               cv.wait(guard, $);
+                       }
+                       guard.unlock($);
+               }
+       }
+
+private:
+       std::atomic<unsigned> count;
+       rl::var<unsigned> waiters;
+       mutex guard;
+       condition_variable_any cv;
+
+       void signal_impl(unsigned cmp)
+       {
+               if (cmp & 0x80000000)
+               {
+                       guard.lock($);
+                       while (false == count($).compare_swap(cmp,
+                               (cmp + 1) & 0x7FFFFFFF, std::memory_order_relaxed));
+                       unsigned w = waiters($);
+                       waiters($) = 0;
+                       guard.unlock($);
+                       if (w)
+                               cv.notify_all($);
+               }
+       }
+};