intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 35 insertions, 0 deletions

diff --git a/library/cpp/threading/queue/mpsc_intrusive_unordered.h b/library/cpp/threading/queue/mpsc_intrusive_unordered.h
new file mode 100644
index 0000000000..6ac7537ae9
--- /dev/null
+++ b/library/cpp/threading/queue/mpsc_intrusive_unordered.h
@@ -0,0 +1,35 @@
+#pragma once
+
+/*
+  Simple almost-wait-free unordered queue for low contention operations.
+
+  It's wait-free for producers.
+  Hanging producer can hide some items from consumer.
+ */
+
+#include <util/system/types.h>
+
+namespace NThreading {
+    struct TIntrusiveNode {
+        TIntrusiveNode* Next;
+    };
+
+    class TMPSCIntrusiveUnordered {
+    public:
+        static constexpr ui32 NUMBER_OF_TRIES_FOR_CAS = 3;
+
+        void Push(TIntrusiveNode* node) noexcept;
+        TIntrusiveNode* PopMany() noexcept;
+        TIntrusiveNode* Pop() noexcept;
+
+        void Push(void* node) noexcept {
+            Push(reinterpret_cast<TIntrusiveNode*>(node));
+        }
+
+    private:
+        TIntrusiveNode* HeadForCaS = nullptr;
+        TIntrusiveNode* HeadForSwap = nullptr;
+        TIntrusiveNode* NotReadyChain = nullptr;
+        TIntrusiveNode* PopOneQueue = nullptr;
+    };
+}