fix ps cache process data thread can not exit

mindspore/ccsrc/ps/ps_cache/ps_cache_manager.cc

@@ -353,7 +353,10 @@ bool PsCacheManager::ProcessData() {
   struct timeval start_time, end_time;
   const uint64_t kUSecondInSecond = 1000000;
   (void)gettimeofday(&start_time, nullptr);
-  auto data = PsDataPrefetch::GetInstance().data(channel_name_);
+  void *data = nullptr;
+  if (!PsDataPrefetch::GetInstance().QueryData(channel_name_, &data)) {
+    return false;
+  }
   if (data == nullptr) {
     MS_LOG(INFO) << "No data process, channel name:" << channel_name_;
     std::unique_lock<std::mutex> locker(data_mutex_);

mindspore/ccsrc/ps/ps_cache/ps_data/ps_data_prefetch.cc

@@ -53,6 +53,7 @@ bool PsDataPrefetch::PrefetchData(const std::string &channel_name, void *data, c
   const std::string supported_data_type = "int32";
   if (data_type != supported_data_type) {
     MS_LOG(ERROR) << "Parameter server cache mode need input id with data type[int32], but got[" << data_type << "]";
+    invalid_data_type_ = true;
     return false;
   }
   if (data == nullptr) {
@@ -105,12 +106,20 @@ bool PsDataPrefetch::FinalizeData(const std::string &channel_name) {
   return false;
 }
 
-void *PsDataPrefetch::data(const std::string &channel_name) const {
+bool PsDataPrefetch::QueryData(const std::string &channel_name, void **data_ptr) const {
+  if (invalid_data_type_) {
+    return false;
+  }
+  if (data_ptr == nullptr) {
+    return false;
+  }
   auto channel = ps_data_channel(channel_name);
   if (channel == nullptr) {
-    return nullptr;
+    *data_ptr = nullptr;
+    return true;
   }
-  return channel->data();
+  *data_ptr = channel->data();
+  return true;
 }
 
 size_t PsDataPrefetch::data_size(const std::string &channel_name) const {

mindspore/ccsrc/ps/ps_cache/ps_data/ps_data_prefetch.h

@@ -41,7 +41,7 @@ class EXPORT PsDataPrefetch {
                            const std::string &data_type);
   EXPORT bool FinalizeData(const std::string &channel_name);
   EXPORT void NotifyFinalize();
-  EXPORT void *data(const std::string &channel_name) const;
+  EXPORT bool QueryData(const std::string &channel_name, void **data_ptr) const;
   EXPORT size_t data_size(const std::string &channel_name) const;
   EXPORT bool TryWakeChannel(const std::string &channel_name);
 
@@ -59,6 +59,7 @@ class EXPORT PsDataPrefetch {
   std::condition_variable data_prefetch_;
   std::condition_variable data_process_;
   std::atomic_bool need_wait_{true};
+  std::atomic_bool invalid_data_type_{false};
 };
 }  // namespace ps
 }  // namespace mindspore