[pulseaudio-discuss] [PATCH v2] bluez5-util: fix profile waiting logic

[Tanu Kaskinen]

There were two bugs in the old logic. The first one:

If a device has two profiles, the old code would start the wait timer
when the first profile connects, but when the second profile connects,
the timer would not get stopped and the CONNECTION_CHANGED hook would
not get fired, because the code for that was inside an if block that
only gets executed when the first profile connects. As a result,
module-bluez5-device loading would always be delayed until the wait
timeout expires.

The second bug:

A crash was observed in device_start_waiting_for_profiles(). That
function is called whenever the connected profile count changes from 0
to 1. The function also has an assertion that checks that the timer is
not running when the function is called. That assertion crashed in the
following scenario with a headset that supports HSP and A2DP:

1. First HSP gets connected. The timer is started.

2. Then HSP gets disconnected for some reason. The timer is still
running.

3. Then A2DP gets connected. device_start_waiting_for_profiles() is
called, because the connected profile count changed from 0 to 1 again.
The timer is already running, so the assertion fails.

First I thought I'd remove the assertion from
device_start_waiting_for_profiles() and just restart the timer on the
second call, but then I figured that when the device returns to the
"everything disconnected" state in step 2, it would be better to stop
the timer. The purpose of the timer is to delay the notification of the
device becoming connected, but if the device becomes disconnected during
the waiting period, the notification doesn't make sense any more, and
therefore the timer doesn't make sense either.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=100237
---
 src/modules/bluetooth/bluez5-util.c | 49 ++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 14 deletions(-)

Changes in v2:
 - Rewrote the patch so that it also fixes the crash bug.

diff --git a/src/modules/bluetooth/bluez5-util.c b/src/modules/bluetooth/bluez5-util.c
index 7d63f35a0..47973b81c 100644
--- a/src/modules/bluetooth/bluez5-util.c
+++ b/src/modules/bluetooth/bluez5-util.c
@@ -259,6 +259,9 @@ static void device_start_waiting_for_profiles(pa_bluetooth_device *device) {
 
 void pa_bluetooth_transport_set_state(pa_bluetooth_transport *t, pa_bluetooth_transport_state_t state) {
     bool old_any_connected;
+    unsigned n_disconnected_profiles;
+    bool new_device_appeared;
+    bool device_disconnected;
 
     pa_assert(t);
 
@@ -274,26 +277,44 @@ void pa_bluetooth_transport_set_state(pa_bluetooth_transport *t, pa_bluetooth_tr
 
     pa_hook_fire(&t->device->discovery->hooks[PA_BLUETOOTH_HOOK_TRANSPORT_STATE_CHANGED], t);
 
-    if (old_any_connected != pa_bluetooth_device_any_transport_connected(t->device)) {
-        unsigned n_disconnected_profiles;
+    /* If there are profiles that are expected to get connected soon (based
+     * on the UUID list), we wait for a bit before announcing the new
+     * device, so that all profiles have time to get connected before the
+     * card object is created. If we didn't wait, the card would always
+     * have only one profile marked as available in the initial state,
+     * which would prevent module-card-restore from restoring the initial
+     * profile properly. */
 
-        /* If there are profiles that are expected to get connected soon (based
-         * on the UUID list), we wait for a bit before announcing the new
-         * device, so that all profiles have time to get connected before the
-         * card object is created. If we didn't wait, the card would always
-         * have only one profile marked as available in the initial state,
-         * which would prevent module-card-restore from restoring the initial
-         * profile properly. */
+    n_disconnected_profiles = device_count_disconnected_profiles(t->device);
 
-        n_disconnected_profiles = device_count_disconnected_profiles(t->device);
+    new_device_appeared = !old_any_connected && pa_bluetooth_device_any_transport_connected(t->device);
+    device_disconnected = old_any_connected && !pa_bluetooth_device_any_transport_connected(t->device);
 
-        if (n_disconnected_profiles == 0)
-            device_stop_waiting_for_profiles(t->device);
-
-        if (!old_any_connected && n_disconnected_profiles > 0)
+    if (new_device_appeared) {
+        if (n_disconnected_profiles > 0)
             device_start_waiting_for_profiles(t->device);
         else
             pa_hook_fire(&t->device->discovery->hooks[PA_BLUETOOTH_HOOK_DEVICE_CONNECTION_CHANGED], t->device);
+        return;
+    }
+
+    if (device_disconnected) {
+        if (t->device->wait_for_profiles_timer) {
+            /* If the timer is still running when the device disconnects, we
+             * never sent the notification of the device getting connected, so
+             * we don't need to send a notification about the disconnection
+             * either. Let's just stop the timer. */
+            device_stop_waiting_for_profiles(t->device);
+        } else
+            pa_hook_fire(&t->device->discovery->hooks[PA_BLUETOOTH_HOOK_DEVICE_CONNECTION_CHANGED], t->device);
+        return;
+    }
+
+    if (n_disconnected_profiles == 0 && t->device->wait_for_profiles_timer) {
+        /* All profiles are now connected, so we can stop the wait timer and
+         * send a notification of the new device. */
+        device_stop_waiting_for_profiles(t->device);
+        pa_hook_fire(&t->device->discovery->hooks[PA_BLUETOOTH_HOOK_DEVICE_CONNECTION_CHANGED], t->device);
     }
 }
 
-- 
2.11.0