diff --git a/main.py b/main.py
index f07fab5..8972ba7 100644
--- a/main.py
+++ b/main.py
@@ -146,22 +146,18 @@ async def fastapi_dump_inp(network: str, inp: str) -> bool:
     dump_inp(network, inp)
     return True
 
-app.state.lock = asyncio.Lock()  # Create an async lock object
+app.state.is_simulation = False
 
 # 必须用这个PlainTextResponse，不然每个key都有引号
 @app.get("/runproject/", response_class = PlainTextResponse)
 def fastapi_run_project(network: str) -> str:
-    if app.state.lock.locked():
-        raise HTTPException(status_code=400, detail="is in simulation")
+    if app.state.is_simulation:
+        raise HTTPException(status_code=409, detail="is in simulation")
     else:
-        try:
-            app.state.lock.acquire()  # Acquire the lock
-            result = run_project(network)
-            return result
-        except asyncio.CancelledError:
-            raise HTTPException(status_code=400, detail="is in simulation")
-        finally:
-            app.state.lock.release()
+        app.state.is_simulation = True
+        result = run_project(network)
+        app.state.is_simulation = False
+        return result
 
 # put in inp folder, name without extension
 @app.get("/runinp/")