Refine buffer channel (#8098)

* refine buffer channel

*  refine Receive and Send

* follow comments

paddle/framework/channel.h

@@ -23,8 +23,8 @@ namespace framework {
 template <typename T>
 class Channel {
  public:
-  virtual void Send(T*) = 0;
-  virtual void Receive(T*) = 0;
+  virtual bool Send(T*) = 0;
+  virtual bool Receive(T*) = 0;
   virtual size_t Cap() = 0;
   virtual void Close() = 0;
   virtual ~Channel() {}

paddle/framework/details/buffered_channel.h

@@ -30,8 +30,8 @@ class Buffered : public paddle::framework::Channel<T> {
   friend void paddle::framework::CloseChannel<T>(Channel<T>*);
 
  public:
-  virtual void Send(T*);
-  virtual void Receive(T*);
+  virtual bool Send(T*);
+  virtual bool Receive(T*);
   virtual size_t Cap() { return cap_; }
   virtual void Close();
   virtual ~Buffered();
@@ -48,33 +48,36 @@ class Buffered : public paddle::framework::Channel<T> {
     PADDLE_ENFORCE_GT(cap, 0);
   }
 
-  void NotifyAllSenders(std::unique_lock<std::mutex>*);
   void NotifyAllParticipants(std::unique_lock<std::mutex>*);
 };
 
 template <typename T>
-void Buffered<T>::Send(T* item) {
+bool Buffered<T>::Send(T* item) {
   std::unique_lock<std::mutex> lock(mu_);
   full_cond_var_.wait(lock,
                       [this]() { return channel_.size() < cap_ || closed_; });
+  bool ret = false;
   if (!closed_) {
     channel_.push_back(std::move(*item));
     lock.unlock();
     empty_cond_var_.notify_one();
+    ret = true;
   }
+  return ret;
 }
 
 template <typename T>
-void Buffered<T>::Receive(T* item) {
+bool Buffered<T>::Receive(T* item) {
   std::unique_lock<std::mutex> lock(mu_);
   empty_cond_var_.wait(lock, [this]() { return !channel_.empty() || closed_; });
+  bool ret = false;
   if (!closed_) {
     *item = std::move(channel_.front());
     channel_.pop_front();
-    NotifyAllSenders(&lock);
-  } else {
-    item = nullptr;
+    full_cond_var_.notify_one();
+    ret = true;
   }
+  return ret;
 }
 
 template <typename T>
@@ -92,12 +95,6 @@ Buffered<T>::~Buffered() {
   NotifyAllParticipants(&lock);
 }
 
-template <typename T>
-void Buffered<T>::NotifyAllSenders(std::unique_lock<std::mutex>* lock) {
-  lock->unlock();
-  full_cond_var_.notify_all();
-}
-
 template <typename T>
 void Buffered<T>::NotifyAllParticipants(std::unique_lock<std::mutex>* lock) {
   lock->unlock();

paddle/framework/details/unbuffered_channel.h

@@ -29,8 +29,8 @@ class UnBuffered : public paddle::framework::Channel<T> {
   friend void paddle::framework::CloseChannel<T>(Channel<T>*);
 
  public:
-  virtual void Send(T*);
-  virtual void Receive(T*);
+  virtual bool Send(T*);
+  virtual bool Receive(T*);
   virtual size_t Cap() { return 0; }
   virtual void Close();
   virtual ~UnBuffered();
@@ -57,7 +57,7 @@ class UnBuffered : public paddle::framework::Channel<T> {
 // This function implements the concept of how data should
 // be sent from a writer to a reader.
 template <typename T>
-void UnBuffered<T>::Send(T* data) {
+bool UnBuffered<T>::Send(T* data) {
   // Prevent other writers from entering
   std::unique_lock<std::recursive_mutex> writer_lock(mu_write_);
   writer_found_ = true;
@@ -66,6 +66,7 @@ void UnBuffered<T>::Send(T* data) {
   cv_writer_.wait(cv_lock,
                   [this]() { return reader_found_ == true || closed_; });
   cv_reader_.notify_one();
+  bool ret = false;
   if (!closed_) {
     std::unique_lock<std::mutex> channel_lock(mu_ch_);
     item = data;
@@ -74,14 +75,16 @@ void UnBuffered<T>::Send(T* data) {
     channel_lock.lock();
     cv_channel_.wait(channel_lock,
                      [this]() { return item == nullptr || closed_; });
+    ret = true;
   }
   writer_found_ = false;
+  return ret;
 }
 
 // This function implements the concept of how
 // data that was sent by a writer is read from a reader.
 template <typename T>
-void UnBuffered<T>::Receive(T* data) {
+bool UnBuffered<T>::Receive(T* data) {
   // Prevent other readers from entering
   std::unique_lock<std::recursive_mutex> read_lock{mu_read_};
   reader_found_ = true;
@@ -90,6 +93,7 @@ void UnBuffered<T>::Receive(T* data) {
   cv_reader_.wait(cv_lock,
                   [this]() { return writer_found_ == true || closed_; });
   cv_writer_.notify_one();
+  bool ret = false;
   if (!closed_) {
     std::unique_lock<std::mutex> lock_ch{mu_ch_};
     // Reader should wait for the writer to first write its data
@@ -98,10 +102,12 @@ void UnBuffered<T>::Receive(T* data) {
       *data = std::move(*item);
       item = nullptr;
       lock_ch.unlock();
+      ret = true;
     }
     cv_channel_.notify_one();
   }
   reader_found_ = false;
+  return ret;
 }
 
 // This function implements the sequence of events