Update lock-free queue for multi-threading, add remove task process in the wait method of Task. #436

kevingpqi123 · 2025-01-20T12:38:32Z

No description provided.

…n the wait method of Task.

domchen · 2025-01-21T01:04:33Z

include/tgfx/core/Task.h

+  /**
+   * Returns true if the Task is currently waiting to execute its code block.
+   */
+  bool waiting();


不需要这个接口

domchen · 2025-01-21T01:05:41Z

include/tgfx/core/Task.h

@@ -67,10 +73,10 @@ class Task {
  void wait();

 private:
+  enum class TaskStatus { waiting, executing, finished, cancelled };


不能叫waiting，有歧义。用queuing.

domchen · 2025-01-21T01:07:54Z

src/core/utils/LockFreeQueue.h

-  LockFreeQueue() {
-    queuePool = reinterpret_cast<T*>(std::calloc(QUEUE_SIZE, sizeof(T)));
+  /**
+   * capacity needs to be a power of 2, otherwise the implementation of getIndex needs to be changed.


The capacity

domchen · 2025-01-21T01:08:33Z

src/core/utils/LockFreeQueue.h

+   * capacity needs to be a power of 2, otherwise the implementation of getIndex needs to be changed.
+   * @param capacity
+   */
+  explicit LockFreeQueue(uint32_t capacity) : _capacity(capacity) {


这里要给capacity加个ASSERT()检查是不是2的指数，或者自动吸附到指数。

domchen · 2025-01-21T01:11:50Z

src/core/utils/Task.cpp

+bool Task::waiting() {
+  return status.load(std::memory_order_relaxed) == TaskStatus::waiting;
+}
+
 bool Task::executing() {
-  std::lock_guard<std::mutex> autoLock(locker);
-  return _executing;
+  return status.load(std::memory_order_relaxed) == TaskStatus::executing;
 }

 bool Task::cancelled() {
-  std::lock_guard<std::mutex> autoLock(locker);
-  return _cancelled;
+  return status.load(std::memory_order_relaxed) == TaskStatus::cancelled;
 }

 bool Task::finished() {
-  std::lock_guard<std::mutex> autoLock(locker);
-  return !_executing && !_cancelled;
+  return status.load(std::memory_order_relaxed) == TaskStatus::finished;
 }


这一排的状态变量可以统一为一个status属性对外暴露。不用单独一个个声明了。

domchen · 2025-01-21T01:16:47Z

src/core/utils/Task.cpp

-    return;
+  auto currentStatus = status.load(std::memory_order_relaxed);
+  if (currentStatus == TaskStatus::waiting) {
+    status.store(TaskStatus::cancelled, std::memory_order_relaxed);


现在没有锁保护了，这里也需要有个CAS，不然不是线程安全的。不能直接就赋值。

domchen · 2025-01-21T01:29:14Z

src/core/utils/Task.cpp

+  if (oldStatus == TaskStatus::waiting) {
+    if (status.compare_exchange_weak(oldStatus, TaskStatus::executing, std::memory_order_acq_rel,
+                                     std::memory_order_relaxed)) {
+      block();


这句之前加一行注释：If wait() is called from the thread pool, all threads might block, leaving no thread to execute this task. To avoid deadlock, execute the task directly on the current thread if it's queued.

domchen · 2025-01-21T03:43:07Z

include/tgfx/core/Task.h

+   * Indicates the current status of the Task. To ensure thread safety, read the data using the
+   * following method: taskStatus.load(std::memory_order_relaxed).
+   */
+  std::atomic<TaskStatus> taskStatus = TaskStatus::queuing;


加个只读方法，不能直接这么暴露出来。

domchen · 2025-01-21T03:47:51Z

src/core/utils/Task.cpp

-    return;
+  auto currentStatus = taskStatus.load(std::memory_order_relaxed);
+  if (currentStatus == TaskStatus::queuing) {
+    while (!taskStatus.compare_exchange_weak(currentStatus, TaskStatus::cancelled,


这里不能while，如果不是queuing状态，就是不能cancel了。

domchen · 2025-01-21T03:52:04Z

src/core/utils/LockFreeQueue.h

+   * power of 2 larger than the capacity.
+   * @param capacity
+   */
+  explicit LockFreeQueue(uint32_t capacity) {


这个Capacity还有一种写法，可以声明到template的参数里， template <typename T, size_t N>, 这样就可以直接声明了。

domchen · 2025-01-21T05:13:00Z

include/tgfx/core/Task.h

+  /**
+   * Return the current status of the Task.
+   */
+  TaskStatus taskStatus() const;


就叫status吧

Update lock-free queue for multi-threading, add remove task process i…

d9be4c5

…n the wait method of Task.

kevingpqi123 requested review from domchen, Hparty and shlzxjp as code owners January 20, 2025 12:38

kevingpqi123 added 2 commits January 20, 2025 20:38

Merge branch 'main' into feature/kevingpqi_threads

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update

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domchen reviewed Jan 21, 2025

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kevingpqi123 added 2 commits January 21, 2025 11:25

Modify the Task interface and improve the implementation.

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update

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domchen reviewed Jan 21, 2025

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Add taskStatus method to the Task class.

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domchen reviewed Jan 21, 2025

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domchen added 2 commits January 21, 2025 13:19

Renmae some methods.

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Add some comments.

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domchen approved these changes Jan 21, 2025

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domchen merged commit ce19888 into main Jan 21, 2025
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domchen deleted the feature/kevingpqi_threads branch January 21, 2025 06:11

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Update lock-free queue for multi-threading, add remove task process in the wait method of Task. #436

Update lock-free queue for multi-threading, add remove task process in the wait method of Task. #436

kevingpqi123 commented Jan 20, 2025

domchen Jan 21, 2025

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domchen Jan 21, 2025

Update lock-free queue for multi-threading, add remove task process in the wait method of Task. #436

Update lock-free queue for multi-threading, add remove task process in the wait method of Task. #436

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kevingpqi123 commented Jan 20, 2025

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