架构设计
- 监控模块:负责定期检查线程状态,收集线程的锁持有和等待信息。
- 检测模块:依据监控模块收集的数据,使用特定算法检测是否存在死锁。
- 恢复模块:一旦检测到死锁,执行恢复策略,使系统恢复正常运行。
关键算法
- 资源分配图算法:将线程和锁视为节点,线程对锁的请求和持有关系视为边,构建资源分配图。通过算法(如深度优先搜索)检测图中是否存在环,若存在环则表明可能存在死锁。
- 超时检测:为每个锁请求设置超时时间,如果线程等待锁的时间超过该超时时间,认为可能出现死锁。
代码实现思路
- 监控模块
import threading
import time
lock_monitor = {}
def monitor_locks():
while True:
for thread in threading.enumerate():
if hasattr(thread, 'lock_held'):
for lock in thread.lock_held:
lock_monitor.setdefault(lock, []).append(thread)
if hasattr(thread, 'lock_waiting'):
for lock in thread.lock_waiting:
lock_monitor.setdefault(lock, []).append(None)
time.sleep(1) # 定期检查
- 检测模块
def detect_deadlock():
# 构建资源分配图
graph = {}
for lock, threads in lock_monitor.items():
for i, thread in enumerate(threads):
if thread is None:
continue
if thread not in graph:
graph[thread] = []
for other_thread in threads[:i] + threads[i+1:]:
if other_thread is not None:
graph[thread].append(other_thread)
# 使用深度优先搜索检测环
visited = set()
recursion_stack = set()
def is_cyclic(node):
visited.add(node)
recursion_stack.add(node)
for neighbor in graph.get(node, []):
if neighbor not in visited:
if is_cyclic(neighbor):
return True
elif neighbor in recursion_stack:
return True
recursion_stack.remove(node)
return False
for thread in graph:
if thread not in visited:
if is_cyclic(thread):
return True
return False
- 恢复模块
def recover_from_deadlock():
# 简单恢复策略,终止死锁线程
for thread in threading.enumerate():
if hasattr(thread, 'is_deadlocked') and thread.is_deadlocked:
thread.terminate() # 实际中需要合适的终止方法