[GitHub] [tvm] junrushao1994 commented on a change in pull request #10234: [Runtime][Pipeline Executor] multiple threads management and the data forwarding notification mechanism.

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junrushao1994 commented on a change in pull request #10234:
URL: https://github.com/apache/tvm/pull/10234#discussion_r812554431



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File path: src/runtime/pipeline/pipeline_struct.h
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@@ -42,6 +52,75 @@ using GlobalOutputPair = std::pair<int, int>;
  * The first 'int' is the module index, and the second 'int' is the module output index.
  */
 using ModuleOutputPair = std::pair<int, int>;
+/*!
+ *\brief The pair includes the module index and the module input index.
+ * The first 'int' is the module index, and the second 'int' is the module input index.
+ */
+using ModuleInputPair = std::pair<int, int>;
+/*!\brief The data notification structure.*/
+class DataNotify {
+ private:
+  /*!\brief The 'contitional variable' is used to wait for notification.*/
+  std::condition_variable condition_;
+  /*!\brief The mutex is used to protect the 'conditional variable'.*/
+  std::mutex mutex_;
+  /*!\brief Whether a data is ready or not.*/
+  volatile bool data_ready_ = false;
+  /*!\brief Whether the thread should exit or not.*/
+  volatile bool exit_state_ = false;

Review comment:
       volatile has nothing to do with multi-threading or memory fence. it's only used in modern c++ to enforce reading from memory and disallow compilers to put the specific data from the register. Note that no memory fence is required to be introduced by volatile, so it doesn't officially guarantee anything about visibility. The rule of thumb is to never use volatile unless for usecases like DMA




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