Add lock around handlers list

mattsaxon · Apr 10, 2020 · d8f3508 · d8f3508
1 parent dc570c9
commit d8f3508
Showing 1 changed file with 29 additions and 25 deletions.
diff --git a/zeroconf/__init__.py b/zeroconf/__init__.py
@@ -1384,6 +1384,7 @@ def __init__(
         self.next_time = current_time_millis()
         self.delay = delay
         self._handlers_to_call = []  # type: List[List[Any]]
+        self._handler_lock = threading.Lock()
 
         self._service_state_changed = Signal()
 
@@ -1436,42 +1437,44 @@ def update_record(self, zc: 'Zeroconf', now: float, record: DNSRecord) -> None:
 
         def enqueue_callback(state_change: ServiceStateChange, name: str) -> None:
 
-            if state_change == ServiceStateChange.Updated:
+            with self._handler_lock:
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
-                    return
+                if state_change == ServiceStateChange.Updated:
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
-                    warnings.warn("not adding update as adding", DeprecationWarning)
-                    return
+                    if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
+                        return
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
-                    return
+                    if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
+                        warnings.warn("not adding update as adding", DeprecationWarning)
+                        return
 
-            elif state_change == ServiceStateChange.Added:
+                    if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
+                        return
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
-                    self._handlers_to_call.remove([name, ServiceStateChange.Removed])
+                elif state_change == ServiceStateChange.Added:
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
-                    warnings.warn("removing update as adding", DeprecationWarning)
-                    self._handlers_to_call.remove([name, ServiceStateChange.Updated])
+                    if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
+                        self._handlers_to_call.remove([name, ServiceStateChange.Removed])
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
-                    return
+                    if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
+                        warnings.warn("removing update as adding", DeprecationWarning)
+                        self._handlers_to_call.remove([name, ServiceStateChange.Updated])
 
-            elif state_change == ServiceStateChange.Removed:
+                    if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
+                        return
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
-                    self._handlers_to_call.remove([name, ServiceStateChange.Added])
+                elif state_change == ServiceStateChange.Removed:
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
-                    self._handlers_to_call.remove([name, ServiceStateChange.Updated])
+                    if self._handlers_to_call.count([name, ServiceStateChange.Added]) == 1:
+                        self._handlers_to_call.remove([name, ServiceStateChange.Added])
 
-                if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
-                    return
+                    if self._handlers_to_call.count([name, ServiceStateChange.Updated]) == 1:
+                        self._handlers_to_call.remove([name, ServiceStateChange.Updated])
+
+                    if self._handlers_to_call.count([name, ServiceStateChange.Removed]) == 1:
+                        return
 
-            self._handlers_to_call.append([name, state_change])
+                self._handlers_to_call.append([name, state_change])
 
         if record.type == _TYPE_PTR and record.name == self.type:
             assert isinstance(record, DNSPointer)
@@ -1539,7 +1542,8 @@ def run(self) -> None:
                 self.delay = min(_BROWSER_BACKOFF_LIMIT * 1000, self.delay * 2)
 
             if len(self._handlers_to_call) > 0 and not self.zc.done:
-                handler = self._handlers_to_call.pop(0)
+                with self._handler_lock:
+                    handler = self._handlers_to_call.pop(0)
                 self._service_state_changed.fire(
                     zeroconf=self.zc, service_type=self.type, name=handler[0], state_change=handler[1]
                 )