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fix BlueZ wait condition disconnect race #1399

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merged 3 commits into from
Aug 28, 2023
Merged

fix BlueZ wait condition disconnect race #1399

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276ef78
backends/bluezdbus/manager: normalize adapter/device arg checks
dlech Aug 25, 2023
9a182ed
backends/bluezdbus/manager: race InterfaceRemoved in _wait_for_servic…
dlech Aug 25, 2023
edfbd93
backends/bluezdbus/manager: add device path to condition callbacks
dlech Aug 25, 2023
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2 changes: 2 additions & 0 deletions CHANGELOG.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ Changed
* Scanner backends modified to allow multiple advertisement callbacks. Merged #1367.
* Changed default handling of the ``response`` argument in ``BleakClient.write_gatt_char``.
Fixes #909.
* Changed `BlueZManager` methods to raise `BleakError` when device is not in BlueZ.

Fixed
-----
Expand All @@ -31,6 +32,7 @@ Fixed
* Fixed typing for ``BaseBleakScanner`` detection callback.
* Fixed possible crash in ``_stopped_handler()`` in WinRT backend. Fixes #1330.
* Reduced expensive logging in the BlueZ backend. Merged #1376.
* Fixed race condition with ``"InterfaceRemoved"`` when getting services in BlueZ backend.

`0.20.2`_ (2023-04-19)
======================
Expand Down
149 changes: 126 additions & 23 deletions bleak/backends/bluezdbus/manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
"""

import asyncio
import contextlib
import logging
import os
from typing import (
Expand Down Expand Up @@ -66,6 +67,12 @@ class CallbackAndState(NamedTuple):
"""


DevicePropertiesChangedCallback = Callable[[], None]
"""
A callback that is called when the properties of a device change in BlueZ.
"""


DeviceRemovedCallback = Callable[[str], None]
"""
A callback that is called when a device is removed from BlueZ.
Expand Down Expand Up @@ -167,9 +174,25 @@ def __init__(self):
self._advertisement_callbacks: List[CallbackAndState] = []
self._device_removed_callbacks: List[DeviceRemovedCallbackAndState] = []
self._device_watchers: Set[DeviceWatcher] = set()
self._condition_callbacks: Set[Callable] = set()
self._condition_callbacks: Dict[str, Set[DevicePropertiesChangedCallback]] = {}
self._services_cache: Dict[str, BleakGATTServiceCollection] = {}

def _check_adapter(self, adapter_path: str) -> None:
"""
Raises:
BleakError: if adapter is not present in BlueZ
"""
if adapter_path not in self._properties:
raise BleakError(f"adapter '{adapter_path.split('/')[-1]}' not found")

def _check_device(self, device_path: str) -> None:
"""
Raises:
BleakError: if device is not present in BlueZ
"""
if device_path not in self._properties:
raise BleakError(f"device '{device_path.split('/')[-1]}' not found")

async def async_init(self):
"""
Connects to the D-Bus message bus and begins monitoring signals.
Expand Down Expand Up @@ -326,13 +349,15 @@ async def active_scan(

Returns:
An async function that is used to stop scanning and remove the filters.

Raises:
BleakError: if the adapter is not present in BlueZ
"""
async with self._bus_lock:
# If the adapter doesn't exist, then the message calls below would
# fail with "method not found". This provides a more informative
# error message.
if adapter_path not in self._properties:
raise BleakError(f"adapter '{adapter_path.split('/')[-1]}' not found")
self._check_adapter(adapter_path)

callback_and_state = CallbackAndState(advertisement_callback, adapter_path)
self._advertisement_callbacks.append(callback_and_state)
Expand Down Expand Up @@ -432,13 +457,15 @@ async def passive_scan(

Returns:
An async function that is used to stop scanning and remove the filters.

Raises:
BleakError: if the adapter is not present in BlueZ
"""
async with self._bus_lock:
# If the adapter doesn't exist, then the message calls below would
# fail with "method not found". This provides a more informative
# error message.
if adapter_path not in self._properties:
raise BleakError(f"adapter '{adapter_path.split('/')[-1]}' not found")
self._check_adapter(adapter_path)

callback_and_state = CallbackAndState(advertisement_callback, adapter_path)
self._advertisement_callbacks.append(callback_and_state)
Expand Down Expand Up @@ -534,7 +561,12 @@ def add_device_watcher(

Returns:
A device watcher object that acts a token to unregister the watcher.

Raises:
BleakError: if the device is not present in BlueZ
"""
self._check_device(device_path)

watcher = DeviceWatcher(
device_path, on_connected_changed, on_characteristic_value_changed
)
Expand Down Expand Up @@ -571,7 +603,12 @@ async def get_services(

Returns:
A new :class:`BleakGATTServiceCollection`.

Raises:
BleakError: if the device is not present in BlueZ
"""
self._check_device(device_path)

if use_cached:
services = self._services_cache.get(device_path)
if services is not None:
Expand Down Expand Up @@ -644,7 +681,12 @@ def get_device_name(self, device_path: str) -> str:

Returns:
The current property value.

Raises:
BleakError: if the device is not present in BlueZ
"""
self._check_device(device_path)

return self._properties[device_path][defs.DEVICE_INTERFACE]["Name"]

def is_connected(self, device_path: str) -> bool:
Expand All @@ -655,7 +697,7 @@ def is_connected(self, device_path: str) -> bool:
device_path: The D-Bus object path of the device.

Returns:
The current property value.
The current property value or ``False`` if the device does not exist in BlueZ.
"""
try:
return self._properties[device_path][defs.DEVICE_INTERFACE]["Connected"]
Expand All @@ -667,23 +709,76 @@ async def _wait_for_services_discovery(self, device_path: str) -> None:
Waits for the device services to be discovered.

If a disconnect happens before the completion a BleakError exception is raised.

Raises:
BleakError: if the device is not present in BlueZ
"""
services_discovered_wait_task = asyncio.create_task(
self._wait_condition(device_path, "ServicesResolved", True)
)
device_disconnected_wait_task = asyncio.create_task(
self._wait_condition(device_path, "Connected", False)
)
done, pending = await asyncio.wait(
{services_discovered_wait_task, device_disconnected_wait_task},
return_when=asyncio.FIRST_COMPLETED,
)
self._check_device(device_path)

with contextlib.ExitStack() as stack:
services_discovered_wait_task = asyncio.create_task(
self._wait_condition(device_path, "ServicesResolved", True)
)
stack.callback(services_discovered_wait_task.cancel)

device_disconnected_wait_task = asyncio.create_task(
self._wait_condition(device_path, "Connected", False)
)
stack.callback(device_disconnected_wait_task.cancel)

for p in pending:
p.cancel()
# in some cases, we can get "InterfaceRemoved" without the
# "Connected" property changing, so we need to race against both
# conditions
device_removed_wait_task = asyncio.create_task(
self._wait_removed(device_path)
)
stack.callback(device_removed_wait_task.cancel)

done, _ = await asyncio.wait(
{
services_discovered_wait_task,
device_disconnected_wait_task,
device_removed_wait_task,
},
return_when=asyncio.FIRST_COMPLETED,
)

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if device_disconnected_wait_task in done:
raise BleakError("failed to discover services, device disconnected")
# check for exceptions
for task in done:
task.result()

if not done.isdisjoint(
{device_disconnected_wait_task, device_removed_wait_task}
):
raise BleakError("failed to discover services, device disconnected")

async def _wait_removed(self, device_path: str) -> None:
"""
Waits for the device interface to be removed.

If the device is not present in BlueZ, this returns immediately.

Args:
device_path: The D-Bus object path of a Bluetooth device.
"""
if device_path not in self._properties:
return

event = asyncio.Event()

def callback(_: str):
event.set()

device_removed_callback_and_state = DeviceRemovedCallbackAndState(
callback, self._properties[device_path][defs.DEVICE_INTERFACE]["Adapter"]
)

with contextlib.ExitStack() as stack:
self._device_removed_callbacks.append(device_removed_callback_and_state)
stack.callback(
self._device_removed_callbacks.remove, device_removed_callback_and_state
)
await event.wait()

async def _wait_condition(
self, device_path: str, property_name: str, property_value: Any
Expand All @@ -695,7 +790,12 @@ async def _wait_condition(
device_path: The D-Bus object path of a Bluetooth device.
property_name: The name of the property to test.
property_value: A value to compare the current property value to.

Raises:
BleakError: if the device is not present in BlueZ
"""
self._check_device(device_path)

if (
self._properties[device_path][defs.DEVICE_INTERFACE][property_name]
== property_value
Expand All @@ -711,13 +811,14 @@ def callback():
):
event.set()

self._condition_callbacks.add(callback)
device_callbacks = self._condition_callbacks.setdefault(device_path, set())
device_callbacks.add(callback)

try:
# can be canceled
await event.wait()
finally:
self._condition_callbacks.remove(callback)
device_callbacks.remove(callback)

def _parse_msg(self, message: Message):
"""
Expand Down Expand Up @@ -851,7 +952,9 @@ def _parse_msg(self, message: Message):
)

# handle device condition watchers
for condition_callback in self._condition_callbacks:
for condition_callback in self._condition_callbacks.get(
message.path, ()
):
condition_callback()

# handle device connection change watchers
Expand Down
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