!6871 [MD] Fix timeout of GeneratorDataset multiprocessing

Merge pull request !6871 from luoyang/pylint

mindspore/dataset/engine/datasets.py

@@ -3279,14 +3279,13 @@ class SamplerFn:
         # Event for end of epoch
         if multi_process is True:
             self.eoe = multiprocessing.Event()
-            self.eof = multiprocessing.Event()
         else:
             self.eoe = threading.Event()
             self.eof = threading.Event()
         # Create workers
         for _ in range(num_worker):
             if multi_process is True:
-                worker = _GeneratorWorkerMp(dataset, self.eoe, self.eof)
+                worker = _GeneratorWorkerMp(dataset, self.eoe)
             else:
                 worker = _GeneratorWorkerMt(dataset, self.eoe, self.eof)
             worker.daemon = True
@@ -3327,15 +3326,40 @@ class SamplerFn:
 
     def __del__(self):
         self.eoe.set()
-        self.eof.set()
         if self.multi_process is False:
+            self.eof.set()
             for w in self.workers:
                 w.join()
 
 
-def _generator_worker_loop(dataset, idx_queue, result_queue, eoe, eof):
+def _generator_worker_loop_mp(dataset, idx_queue, result_queue, eoe):
     """
-    Multiprocessing or multithread generator worker process loop.
+    Multiprocessing generator worker process loop
+    """
+    while True:
+        # Fetch index, block
+        try:
+            idx = idx_queue.get()
+        except KeyboardInterrupt:
+            raise Exception("Generator worker receives KeyboardInterrupt")
+        if idx is None:
+            # When the queue is out of scope from master process, a None item can be fetched from the queue.
+            # Upon receiving None, worker process should check if EOE is set.
+            assert eoe.is_set(), ""
+            return
+        # Fetch data, any exception from __getitem__ will terminate worker and timeout master process
+        result = dataset[idx]
+        # Send data, block
+        try:
+            result_queue.put(result)
+        except KeyboardInterrupt:
+            raise Exception("Generator worker receives KeyboardInterrupt")
+        del result, idx
+
+
+def _generator_worker_loop_mt(dataset, idx_queue, result_queue, eoe, eof):
+    """
+    Multithread generator worker process loop.
     """
     while True:
         # Fetch index, block
@@ -3383,7 +3407,7 @@ class _GeneratorWorkerMt(threading.Thread):
     def __init__(self, dataset, eoe, eof):
         self.idx_queue = queue.Queue(16)
         self.res_queue = queue.Queue(16)
-        super().__init__(target=_generator_worker_loop, args=(dataset, self.idx_queue, self.res_queue, eoe, eof))
+        super().__init__(target=_generator_worker_loop_mt, args=(dataset, self.idx_queue, self.res_queue, eoe, eof))
 
     def put(self, item):
         """
@@ -3403,10 +3427,10 @@ class _GeneratorWorkerMp(multiprocessing.Process):
     Worker process for multiprocess Generator.
     """
 
-    def __init__(self, dataset, eoe, eof):
+    def __init__(self, dataset, eoe):
         self.idx_queue = multiprocessing.Queue(16)
         self.res_queue = multiprocessing.Queue(16)
-        super().__init__(target=_generator_worker_loop, args=(dataset, self.idx_queue, self.res_queue, eoe, eof))
+        super().__init__(target=_generator_worker_loop_mp, args=(dataset, self.idx_queue, self.res_queue, eoe))
 
     def put(self, item):
         """