[Bug Fix][HiCache] TreeNode.get_prefix_hash_values @lru_cache can return mutated list (#26177)

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

python/sglang/srt/mem_cache/mamba_radix_cache.py

@@ -22,7 +22,6 @@ The radix tree data structure for managing the hybrid (full and Mamba) KV cache.
 import heapq
 from array import array
 from collections import defaultdict
-from functools import lru_cache
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
 import torch
@@ -148,7 +147,6 @@ class TreeNode:
             return None
         return self.hash_value[-1]
 
-    @lru_cache(maxsize=1)
     def get_prefix_hash_values(self, node: "TreeNode") -> List[str]:
         if node is None or node.hash_value is None:
             return []

python/sglang/srt/mem_cache/radix_cache.py

@@ -28,7 +28,6 @@ import sys
 import time
 from array import array
 from collections import defaultdict
-from functools import lru_cache
 from typing import TYPE_CHECKING, Any, Iterator, List, Optional, Tuple, Union
 
 import torch
@@ -258,7 +257,6 @@ class TreeNode:
             return None
         return self.hash_value[-1]
 
-    @lru_cache(maxsize=1)
     def get_prefix_hash_values(self, node: TreeNode) -> List[str]:
         if node is None or node.hash_value is None:
             return []