From 26141d0353503b2852a1d1dcfcb3bf93d3050977 Mon Sep 17 00:00:00 2001 From: Matthew Wolter Date: Sun, 12 Apr 2026 03:56:09 -0700 Subject: [PATCH] =?UTF-8?q?G5:=20F05=20=E2=80=94=20track=20fire-and-forget?= =?UTF-8?q?=20asyncio.create=5Ftask=20references?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Why: Python's asyncio holds only weak references to tasks created via create_task(). Under GC pressure (especially Python < 3.11), unretained tasks can be silently cancelled mid-execution, and any exceptions are swallowed as "Task exception was never retrieved." Seven call sites across TCPConnection, BLEConnection, SerialConnection, and EventDispatcher used fire-and-forget create_task with no stored reference. Fix: introduce _background_tasks set and _spawn_background() helper on each class, following the standard pattern from the asyncio docs (task.add_done_callback(set.discard)). Refs: Forensics report finding F05 --- src/meshcore/ble_cx.py | 12 ++++++++++-- src/meshcore/events.py | 10 +++++++++- src/meshcore/serial_cx.py | 12 ++++++++++-- src/meshcore/tcp_cx.py | 12 ++++++++++-- 4 files changed, 39 insertions(+), 7 deletions(-) diff --git a/src/meshcore/ble_cx.py b/src/meshcore/ble_cx.py index 0ce06d9..86df64d 100644 --- a/src/meshcore/ble_cx.py +++ b/src/meshcore/ble_cx.py @@ -51,6 +51,14 @@ class BLEConnection: self.pin = pin self.rx_char = None self._disconnect_callback = None + self._background_tasks: set[asyncio.Task] = set() + + def _spawn_background(self, coro) -> asyncio.Task: + """Create a tracked background task (prevents GC of fire-and-forget tasks).""" + task = asyncio.create_task(coro) + self._background_tasks.add(task) + task.add_done_callback(self._background_tasks.discard) + return task async def connect(self): """ @@ -155,7 +163,7 @@ class BLEConnection: self.device = self._user_provided_device if self._disconnect_callback: - asyncio.create_task(self._disconnect_callback("ble_disconnect")) + self._spawn_background(self._disconnect_callback("ble_disconnect")) def set_disconnect_callback(self, callback): """Set callback to handle disconnections.""" @@ -166,7 +174,7 @@ class BLEConnection: def handle_rx(self, _: BleakGATTCharacteristic, data: bytearray): if self.reader is not None: - asyncio.create_task(self.reader.handle_rx(data)) + self._spawn_background(self.reader.handle_rx(data)) async def send(self, data): if not self.client: diff --git a/src/meshcore/events.py b/src/meshcore/events.py index f8a7521..2f23338 100644 --- a/src/meshcore/events.py +++ b/src/meshcore/events.py @@ -134,6 +134,14 @@ class EventDispatcher: self.subscriptions: List[Subscription] = [] self.running = False self._task = None + self._background_tasks: set[asyncio.Task] = set() + + def _spawn_background(self, coro) -> asyncio.Task: + """Create a tracked background task (prevents GC of fire-and-forget tasks).""" + task = asyncio.create_task(coro) + self._background_tasks.add(task) + task.add_done_callback(self._background_tasks.discard) + return task def subscribe( self, @@ -197,7 +205,7 @@ class EventDispatcher: # returns - avoids the race where create_task schedules the callback after # the waiter has already timed out with done=set(). if asyncio.iscoroutinefunction(subscription.callback): - asyncio.create_task(self._execute_callback(subscription.callback, event.clone())) + self._spawn_background(self._execute_callback(subscription.callback, event.clone())) else: try: subscription.callback(event.clone()) diff --git a/src/meshcore/serial_cx.py b/src/meshcore/serial_cx.py index 61163bd..91d65d6 100644 --- a/src/meshcore/serial_cx.py +++ b/src/meshcore/serial_cx.py @@ -20,11 +20,19 @@ class SerialConnection: self._disconnect_callback = None self.cx_dly = cx_dly self._connected_event = asyncio.Event() + self._background_tasks: set[asyncio.Task] = set() self.frame_expected_size = 0 self.inframe = b"" self.header = b"" + def _spawn_background(self, coro) -> asyncio.Task: + """Create a tracked background task (prevents GC of fire-and-forget tasks).""" + task = asyncio.create_task(coro) + self._background_tasks.add(task) + task.add_done_callback(self._background_tasks.discard) + return task + class MCSerialClientProtocol(asyncio.Protocol): def __init__(self, cx): self.cx = cx @@ -44,7 +52,7 @@ class SerialConnection: self.cx._connected_event.clear() if self.cx._disconnect_callback: - asyncio.create_task(self.cx._disconnect_callback("serial_disconnect")) + self.cx._spawn_background(self.cx._disconnect_callback("serial_disconnect")) def pause_writing(self): logger.debug("pause writing") @@ -114,7 +122,7 @@ class SerialConnection: data = data[upbound:] if self.reader is not None: # feed meshcore reader - asyncio.create_task(self.reader.handle_rx(self.inframe)) + self._spawn_background(self.reader.handle_rx(self.inframe)) # reset inframe self.inframe = b"" self.header = b"" diff --git a/src/meshcore/tcp_cx.py b/src/meshcore/tcp_cx.py index 497c3b2..ad9b9cb 100644 --- a/src/meshcore/tcp_cx.py +++ b/src/meshcore/tcp_cx.py @@ -24,6 +24,14 @@ class TCPConnection: self.frame_expected_size = 0 self.header = b"" self.inframe = b"" + self._background_tasks: set[asyncio.Task] = set() + + def _spawn_background(self, coro) -> asyncio.Task: + """Create a tracked background task (prevents GC of fire-and-forget tasks).""" + task = asyncio.create_task(coro) + self._background_tasks.add(task) + task.add_done_callback(self._background_tasks.discard) + return task class MCClientProtocol(asyncio.Protocol): def __init__(self, cx): @@ -47,7 +55,7 @@ class TCPConnection: def connection_lost(self, exc): logger.debug("TCP server closed the connection") if self.cx._disconnect_callback: - asyncio.create_task(self.cx._disconnect_callback("tcp_disconnect")) + self.cx._spawn_background(self.cx._disconnect_callback("tcp_disconnect")) async def connect(self): """ @@ -108,7 +116,7 @@ class TCPConnection: data = data[upbound:] if self.reader is not None: # feed meshcore reader - asyncio.create_task(self.reader.handle_rx(self.inframe)) + self._spawn_background(self.reader.handle_rx(self.inframe)) # reset inframe self.inframe = b"" self.header = b""