diff --git a/mmcv/runner/runner.py b/mmcv/runner/runner.py
index 403cdb22f..c2324ffde 100644
--- a/mmcv/runner/runner.py
+++ b/mmcv/runner/runner.py
@@ -275,6 +275,7 @@ class Runner(object):
         self.data_loader = data_loader
 
         self.call_hook('before_train_epoch')
+        time.sleep(2)  # Prevent possible deadlock during epoch transition
         for i, data_batch in enumerate(data_loader):
             self._inner_iter = i
             self.call_hook('before_train_iter')
@@ -297,7 +298,7 @@ class Runner(object):
         self.mode = 'val'
         self.data_loader = data_loader
         self.call_hook('before_val_epoch')
-
+        time.sleep(2)  # Prevent possible deadlock during epoch transition
         for i, data_batch in enumerate(data_loader):
             self._inner_iter = i
             self.call_hook('before_val_iter')