[mutter] seat-impl: Destroy libinput objects on input thread on tear down

[Marge Bot <marge-bot src gnome org>]

commit 237cdeef4cafc89567f47dcfc5349baf864e295f
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Jan 7 08:31:22 2021 +0100

    seat-impl: Destroy libinput objects on input thread on tear down
    
    We didn't tear down the libinput objects in the right thread when
    exiting, but did so after the input thread exited.
    
    We also tried to destroy the libinput devices after the libinput context
    was destroyed, which isn't allowed.
    
    Fix these two issues by tearing down the libinput objects in a input
    thread task that when done exits the input thread. This effectively
    "flushes" the input thread tasks while destroying the libinput objects
    just before the thread exits.
    
    While it might fine to tear down libinput objects in an arbitrary (main
    in this case) thread while making sure nothing pokes at it in parallel
    (e.g. the input thread is gone), libinput is by definition single
    threaded, and could theoretically make assumptions about this, and we
    shouldn't cause any possible surprises here, so make sure to destroy it
    all in the right thread.
    
    This fixes an abort() on exit caused by an assert about invalid object
    destruction in libinput.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1663>

 src/backends/native/meta-input-device-native.c |  3 +-
 src/backends/native/meta-seat-impl.c           | 43 +++++++++++++++-----------
 2 files changed, 26 insertions(+), 20 deletions(-)
---
diff --git a/src/backends/native/meta-input-device-native.c b/src/backends/native/meta-input-device-native.c
index 04b34c9fee..fb77a07790 100644
--- a/src/backends/native/meta-input-device-native.c
+++ b/src/backends/native/meta-input-device-native.c
@@ -69,8 +69,7 @@ meta_input_device_native_finalize (GObject *object)
 {
   MetaInputDeviceNative *device_evdev = META_INPUT_DEVICE_NATIVE (object);
 
-  if (device_evdev->libinput_device)
-    libinput_device_unref (device_evdev->libinput_device);
+  g_warn_if_fail (!device_evdev->libinput_device);
 
   clear_slow_keys (device_evdev);
   stop_bounce_keys (device_evdev);
diff --git a/src/backends/native/meta-seat-impl.c b/src/backends/native/meta-seat-impl.c
index e419354e11..9e33f70be9 100644
--- a/src/backends/native/meta-seat-impl.c
+++ b/src/backends/native/meta-seat-impl.c
@@ -2750,18 +2750,23 @@ meta_seat_impl_get_property (GObject    *object,
     }
 }
 
-static void
-meta_seat_impl_dispose (GObject *object)
+static gboolean
+destroy_in_impl (GTask *task)
 {
-  MetaSeatImpl *seat_impl = META_SEAT_IMPL (object);
+  MetaSeatImpl *seat_impl = g_task_get_task_data (task);
 
-  if (seat_impl->libinput)
-    {
-      libinput_unref (seat_impl->libinput);
-      seat_impl->libinput = NULL;
-    }
+  g_slist_foreach (seat_impl->devices,
+                   (GFunc) meta_input_device_native_detach_libinput_in_impl,
+                   NULL);
+  g_slist_free_full (seat_impl->devices, g_object_unref);
+  seat_impl->devices = NULL;
 
-  G_OBJECT_CLASS (meta_seat_impl_parent_class)->dispose (object);
+  g_clear_pointer (&seat_impl->libinput, libinput_unref);
+
+  g_main_loop_quit (seat_impl->input_loop);
+  g_task_return_boolean (task, TRUE);
+
+  return G_SOURCE_REMOVE;
 }
 
 static void
@@ -2769,18 +2774,21 @@ meta_seat_impl_finalize (GObject *object)
 {
   MetaSeatImpl *seat_impl = META_SEAT_IMPL (object);
   gboolean numlock_active;
-  GSList *iter;
 
-  g_main_loop_quit (seat_impl->input_loop);
-  g_thread_join (seat_impl->input_thread);
-
-  for (iter = seat_impl->devices; iter; iter = g_slist_next (iter))
+  if (seat_impl->libinput)
     {
-      ClutterInputDevice *device = iter->data;
+      GTask *task;
 
-      g_object_unref (device);
+      task = g_task_new (seat_impl, NULL, NULL, NULL);
+      g_task_set_task_data (task, seat_impl, NULL);
+      meta_seat_impl_run_input_task (seat_impl, task,
+                                     (GSourceFunc) destroy_in_impl);
+      g_object_unref (task);
+
+      g_thread_join (seat_impl->input_thread);
+      g_assert (!seat_impl->libinput);
     }
-  g_slist_free (seat_impl->devices);
+
   g_clear_pointer (&seat_impl->tools, g_hash_table_unref);
 
   if (seat_impl->touch_states)
@@ -2940,7 +2948,6 @@ meta_seat_impl_class_init (MetaSeatImplClass *klass)
   object_class->constructed = meta_seat_impl_constructed;
   object_class->set_property = meta_seat_impl_set_property;
   object_class->get_property = meta_seat_impl_get_property;
-  object_class->dispose = meta_seat_impl_dispose;
   object_class->finalize = meta_seat_impl_finalize;
 
   props[PROP_SEAT] =