ofono/dbus: detach from signals as appropriate

In the dbus_connect() code path, return the subscription token.

In the Modem class, use this token to disconnect signal callbacks when an
interface is removed.

Generalize the signal connect/disconnect handling: have one tuple defining all
signals and their handler functions, add generalized loop to attach them. Store
all subscription tokens in a dict of lists, any number of signal callbacks per
general interface name. When an interface is announced to be removed from
ofono, detach all signals for that interface implicitly.

So far this only handles the MessageManager interface's IncomingMessage signal,
but others will likely follow soon.

Fixes: OS#2242
Change-Id: I0939ef414bc599ee8742df48da04d8d9569d00ba

src/osmo_gsm_tester/ofono_client.py

@@ -17,7 +17,7 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from . import log, test
+from . import log, test, util
 
 from pydbus import SystemBus, Variant
 import time
@@ -37,7 +37,7 @@ class DeferredHandling:
 
     def __init__(self, dbus_iface, handler):
         self.handler = handler
-        dbus_iface.connect(self.receive_signal)
+        self.subscription_id = dbus_iface.connect(self.receive_signal)
 
     def receive_signal(self, *args, **kwargs):
         DeferredHandling.defer_queue.append((self.handler, args, kwargs))
@@ -55,7 +55,7 @@ def dbus_connect(dbus_iface, handler):
     so that a signal handler is invoked only after the DBus polling is through
     by enlisting signals that should be handled in the
     DeferredHandling.defer_queue.'''
-    DeferredHandling(dbus_iface, handler)
+    return DeferredHandling(dbus_iface, handler).subscription_id
 
 
 def poll():
@@ -85,6 +85,7 @@ class Modem(log.Origin):
         self.set_log_category(log.C_BUS)
         self._dbus_obj = None
         self._interfaces = set()
+        self._connected_signals = util.listdict()
         self.sms_received_list = []
         # init interfaces and connect to signals:
         self.dbus_obj()
@@ -149,24 +150,35 @@ class Modem(log.Origin):
         for iface in additions:
             self._on_interface_enabled(iface)
 
+    def _disconnect(self, interface_name):
+        subscriptions = self._connected_signals.pop(interface_name, [])
+        if subscriptions:
+            self.dbg('Disconnecting', len(subscriptions), 'signals from', interface_name)
+        for subscription in subscriptions:
+            subscription.disconnect()
+
     def _on_interface_enabled(self, interface_name):
         self.dbg('Interface enabled:', interface_name)
-        if interface_name == I_SMS:
-            retries = 3
-            while True:
-                try:
-                    dbus_connect(self.dbus_obj()[I_SMS].IncomingMessage, self._on_incoming_message)
-                    break
-                except KeyError:
-                    self.dbg('Interface not yet available:', I_SMS)
-                    retries -= 1
-                    time.sleep(1)
-                    if retries <= 0:
-                        self.err('Interface enabled by signal, but not available:', I_SMS)
-                        raise
+
+        all_wanted_conns = {
+                I_SMS: ( ('IncomingMessage', self._on_incoming_message), ),
+            }
+
+        want = all_wanted_conns.get(interface_name)
+        if not want:
+            return
+
+        # sanity
+        self._disconnect(interface_name)
+
+        self.dbg('Connecting', len(want), 'signals to', interface_name)
+        for signal, cb in want:
+            dbus_iface = getattr(self.dbus_obj()[interface_name], signal)
+            self._connected_signals.add(interface_name, dbus_connect(dbus_iface, cb))
 
     def _on_interface_disabled(self, interface_name):
         self.dbg('Interface disabled:', interface_name)
+        self._disconnect(interface_name)
 
     def has_interface(self, name):
         return name in self._interfaces