bluetooth: fix race condition in BlueZ5 device disconnection

SW: Pulseaudio 8.0 / BlueZ 5.39

Symptoms:
While disconnecting/reconnecting a paired bluetooth headset (LG HBS750)
audio fails roughly on every other connection.

On a failed connection "pactl list cards" shows the bluetooth device's
card but "Active Profile: off". Issuing "pacmd set-card-profile X
a2dp_sink" makes audio work immediately.

I realized that when this happened, the previous disconnection did not
remove the card, instead it was only configured for "Active Profile:
off" but otherwise left in place.

Upon looking at PA debug logs I saw that the transport for the a2dp_sink
was first set into disconnected state and then into idle state. In
"device_connection_changed_cb()" this causes the
"pa_bluetooth_device_any_transport_connected()" return true and the
module-bluez5-device is not unloaded.

Further investigation shows that this is caused by a race of
module-bluez5-device.c:thread_func() and
MediaPoint1::ClearConfiguration().

When the FD in thread_func() is closed (POLLHUP) an
BLUETOOTH_MESSAGE_STREAM_FD_HUP message is sent into the main thread.
The handler of this message unconditionally sets the transport into IDLE
state. This is a problem if it has already been set into DISCONNECTED
state.

diff --git a/src/modules/bluetooth/module-bluez5-device.c b/src/modules/bluetooth/module-bluez5-device.c
index a05ae8d..0914bfb 100644 (file)
--- a/src/modules/bluetooth/module-bluez5-device.c
+++ b/src/modules/bluetooth/module-bluez5-device.c
@@ -2142,7 +2142,8 @@ static int device_process_msg(pa_msgobject *obj, int code, void *data, int64_t o
             pa_assert_se(pa_card_set_profile(m->card, pa_hashmap_get(m->card->profiles, "off"), false) >= 0);
             break;
         case BLUETOOTH_MESSAGE_STREAM_FD_HUP:
-            pa_bluetooth_transport_set_state(u->transport, PA_BLUETOOTH_TRANSPORT_STATE_IDLE);
+            if (u->transport->state > PA_BLUETOOTH_TRANSPORT_STATE_IDLE)
+                pa_bluetooth_transport_set_state(u->transport, PA_BLUETOOTH_TRANSPORT_STATE_IDLE);
             break;
     }