fix(hiradix): wait for extra pool IO (#27550)

Co-authored-by: Zhangheng <hzh0425@apache.org>

python/sglang/srt/mem_cache/hiradix_cache.py

@@ -1342,6 +1342,13 @@ class HiRadixCache(RadixCache):
             # unknown prefetch stop policy, just return True
             return True
 
+        if (
+            completed
+            and getattr(operation, "pool_transfers", None)
+            and not getattr(operation, "pool_transfers_done", True)
+        ):
+            can_terminate = False
+
         operation_terminated = operation.is_terminated()
         states = torch.tensor(
             [1 - int(can_terminate), int(operation_terminated)],