From 7e8d3a9c491d883ce8aeba25c5aaba24b7c04124 Mon Sep 17 00:00:00 2001
From: ThearchyHelios <work@thearchyhelios.com>
Date: Fri, 16 Oct 2026 17:46:20 +0800
Subject: [PATCH] =?UTF-8?q?=E5=8F=A3=E5=BE=84=E6=AF=94=E5=AF=B9=E7=9A=84?=
 =?UTF-8?q?=20drain=EF=BC=88=E6=B5=8B=E8=AF=95=E7=94=A8=EF=BC=89=E5=8F=AA?=
 =?UTF-8?q?=E7=AD=89=E8=BF=98=E6=B2=A1=E5=81=9A=E5=AE=8C=E7=9A=84=E4=BB=BB?=
 =?UTF-8?q?=E5=8A=A1=EF=BC=8C=E5=81=9A=E5=AE=8C=E8=BF=98=E7=95=99=E5=9C=A8?=
 =?UTF-8?q?=E7=99=BB=E8=AE=B0=E9=87=8C=E7=9A=84=E9=A1=BA=E6=89=8B=E5=8E=BB?=
 =?UTF-8?q?=E6=8E=89?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

为什么：并行跑全量测试时偶发过 drain 原地空转（faulthandler 抓到主线程一直在 drain 里，每轮 gather 都立刻返回），四次全量里挂了两次。这一波起整题等价的探索运行比完会接着自动出具，后台任务的进出更密。改成只 gather 没做完的、把做完的从登记里去掉之后，连跑两次全量都没再出现。drain 只给测试用，服务里不调它；没能在单进程里复现出根因，照实记进遗留。
---
 backend/app/ledger/match.py | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/backend/app/ledger/match.py b/backend/app/ledger/match.py
index fc2643d9..85804248 100644
--- a/backend/app/ledger/match.py
+++ b/backend/app/ledger/match.py
@@ -596,9 +596,17 @@ def _mine() -> list[asyncio.Task[Any]]:
 
 
 async def drain() -> None:
-    """等这个事件循环里的后台比对都做完（测试用）。"""
-    while tasks := _mine():
-        await asyncio.gather(*tasks, return_exceptions=True)
+    """等这个事件循环里的后台比对都做完（测试用）。只等还没做完的：已经做完、还留在登记里的（完成回调还没来得及跑）顺手
+    去掉——不然对着做完的任务反复 gather，事件循环原地空转（并行跑全量测试时偶发过）。"""
+    while True:
+        tasks = _mine()
+        for task in tasks:
+            if task.done():
+                _background.discard(task)
+        live = [task for task in tasks if not task.done()]
+        if not live:
+            return
+        await asyncio.gather(*live, return_exceptions=True)
 
 
 async def shutdown() -> None: