[evolution-data-server] ECalBackend: Deliver component change notifications in a dedicated thread

[Milan Crha <mcrha src gnome org>]

commit 565ba70b04cb205698ce5514cf32fdf7a09bc53e
Author: Milan Crha <mcrha redhat com>
Date:   Mon May 10 19:17:36 2021 +0200

    ECalBackend: Deliver component change notifications in a dedicated thread
    
    Two reasons for it:
    1) there could happen deadlock between the ECalBackendSexp lock and
       the ECalMetaBackend's ECache lock when searching for custom timezones
       and doing two operations at the same time, like deleting and event
       and refreshing the content;
    2) the changes had been verified in the main thread, which could block
       the whole calendar factory.

 src/calendar/libedata-cal/e-cal-backend.c | 298 ++++++++++++++++++++++--------
 1 file changed, 226 insertions(+), 72 deletions(-)
---
diff --git a/src/calendar/libedata-cal/e-cal-backend.c b/src/calendar/libedata-cal/e-cal-backend.c
index ac9f8e9d2..59511940c 100644
--- a/src/calendar/libedata-cal/e-cal-backend.c
+++ b/src/calendar/libedata-cal/e-cal-backend.c
@@ -30,6 +30,9 @@
 
 #include "e-cal-backend.h"
 
+#define NOTIFY_CHANGES_THRESHOLD 50
+#define NOTIFY_CHANGES_TIMEOUT   333
+
 typedef struct _AsyncContext AsyncContext;
 typedef struct _DispatchNode DispatchNode;
 typedef struct _SignalClosure SignalClosure;
@@ -50,6 +53,8 @@ struct _ECalBackendPrivate {
        GProxyResolver *proxy_resolver;
        gchar *cache_dir;
        gboolean writable;
+       GPtrArray *notify_changes; /* NotifyChangesData * */
+       guint changes_timeout_id;
 
        ESource *authentication_source;
        gulong auth_source_changed_handler_id;
@@ -197,6 +202,206 @@ signal_closure_free (SignalClosure *signal_closure)
        g_slice_free (SignalClosure, signal_closure);
 }
 
+typedef enum {
+       NOTIFY_CHANGE_KIND_ADD,
+       NOTIFY_CHANGE_KIND_MODIFY,
+       NOTIFY_CHANGE_KIND_REMOVE
+} NotifyChangeKind;
+
+typedef struct _NotifyChangesData {
+       NotifyChangeKind kind;
+       ECalComponent *old_component;
+       ECalComponent *new_component;
+       ECalComponentId *id;
+} NotifyChangesData;
+
+static NotifyChangesData *
+notify_changes_data_new (NotifyChangeKind kind,
+                        ECalComponent *old_component,
+                        ECalComponent *new_component,
+                        const ECalComponentId *id)
+{
+       NotifyChangesData *ncd;
+
+       if (old_component)
+               g_return_val_if_fail (E_IS_CAL_COMPONENT (old_component), NULL);
+       if (new_component)
+               g_return_val_if_fail (E_IS_CAL_COMPONENT (new_component), NULL);
+
+       ncd = g_slice_new (NotifyChangesData);
+       ncd->kind = kind;
+       ncd->old_component = old_component ? g_object_ref (old_component) : NULL;
+       ncd->new_component = new_component ? g_object_ref (new_component) : NULL;
+       ncd->id = id ? e_cal_component_id_copy (id) : NULL;
+
+       return ncd;
+}
+
+static void
+notify_changes_data_free (gpointer ptr)
+{
+       NotifyChangesData *ncd = ptr;
+
+       if (ncd) {
+               g_clear_object (&ncd->old_component);
+               g_clear_object (&ncd->new_component);
+               e_cal_component_id_free (ncd->id);
+               g_slice_free (NotifyChangesData, ncd);
+       }
+}
+
+static void
+match_view_and_notify_component (EDataCalView *view,
+                                 ECalComponent *old_component,
+                                 ECalComponent *new_component)
+{
+       gboolean old_match = FALSE, new_match = FALSE;
+
+       if (old_component)
+               old_match = e_data_cal_view_component_matches (view, old_component);
+
+       new_match = e_data_cal_view_component_matches (view, new_component);
+
+       if (old_match && new_match)
+               e_data_cal_view_notify_components_modified_1 (view, new_component);
+       else if (new_match)
+               e_data_cal_view_notify_components_added_1 (view, new_component);
+       else if (old_match) {
+               ECalComponentId *id = e_cal_component_get_id (old_component);
+
+               e_data_cal_view_notify_objects_removed_1 (view, id);
+
+               e_cal_component_id_free (id);
+       }
+}
+
+static void
+notify_changes_thread (ECalBackend *cal_backend,
+                      gpointer user_data,
+                      GCancellable *cancellable,
+                      GError **error)
+{
+       GPtrArray *changes;
+       GList *views, *link;
+       guint ii;
+
+       g_mutex_lock (&cal_backend->priv->property_lock);
+
+       changes = cal_backend->priv->notify_changes;
+       cal_backend->priv->notify_changes = NULL;
+
+       g_mutex_unlock (&cal_backend->priv->property_lock);
+
+       if (!changes)
+               return;
+
+       views = e_cal_backend_list_views (cal_backend);
+
+       for (ii = 0; ii < changes->len; ii++) {
+               NotifyChangesData *ncd = g_ptr_array_index (changes, ii);
+
+               switch (ncd->kind) {
+               case NOTIFY_CHANGE_KIND_ADD:
+                       for (link = views; link; link = g_list_next (link)) {
+                               EDataCalView *view = E_DATA_CAL_VIEW (link->data);
+
+                               if (e_data_cal_view_component_matches (view, ncd->new_component))
+                                       e_data_cal_view_notify_components_added_1 (view, ncd->new_component);
+                       }
+                       break;
+               case NOTIFY_CHANGE_KIND_MODIFY:
+                       for (link = views; link; link = g_list_next (link)) {
+                               EDataCalView *view = E_DATA_CAL_VIEW (link->data);
+
+                               match_view_and_notify_component (view, ncd->old_component, 
ncd->new_component);
+                       }
+                       break;
+               case NOTIFY_CHANGE_KIND_REMOVE:
+                       for (link = views; link; link = g_list_next (link)) {
+                               EDataCalView *view = E_DATA_CAL_VIEW (link->data);
+
+                               if (ncd->new_component)
+                                       match_view_and_notify_component (view, ncd->old_component, 
ncd->new_component);
+                               else if (!ncd->old_component)
+                                       e_data_cal_view_notify_objects_removed_1 (view, ncd->id);
+                               else if (e_data_cal_view_component_matches (view, ncd->old_component))
+                                       e_data_cal_view_notify_objects_removed_1 (view, ncd->id);
+                       }
+                       break;
+               }
+       }
+
+       g_list_free_full (views, g_object_unref);
+       g_ptr_array_unref (changes);
+}
+
+static void
+schedule_notify_changes_thread_locked (ECalBackend *cal_backend)
+{
+       e_cal_backend_schedule_custom_operation (cal_backend, NULL,
+               notify_changes_thread, NULL, NULL);
+}
+
+static gboolean
+notify_changes_timeout_cb (gpointer user_data)
+{
+       GWeakRef *weak_ref = user_data;
+       ECalBackend *backend;
+
+       if (g_source_is_destroyed (g_main_current_source ()))
+               return FALSE;
+
+       backend = g_weak_ref_get (weak_ref);
+       if (backend) {
+               g_mutex_lock (&backend->priv->property_lock);
+
+               if (g_source_get_id (g_main_current_source ()) == backend->priv->changes_timeout_id) {
+                       backend->priv->changes_timeout_id = 0;
+                       schedule_notify_changes_thread_locked (backend);
+               }
+
+               g_mutex_unlock (&backend->priv->property_lock);
+
+               g_object_unref (backend);
+       }
+
+       return FALSE;
+}
+
+static void
+schedule_notify_changes (ECalBackend *backend,
+                        NotifyChangeKind kind,
+                        ECalComponent *old_component,
+                        ECalComponent *new_component,
+                        const ECalComponentId *id)
+{
+       NotifyChangesData *ncd;
+
+       ncd = notify_changes_data_new (kind, old_component, new_component, id);
+       g_return_if_fail (ncd != NULL);
+
+       g_mutex_lock (&backend->priv->property_lock);
+
+       if (!backend->priv->notify_changes)
+               backend->priv->notify_changes = g_ptr_array_new_full (NOTIFY_CHANGES_THRESHOLD, 
notify_changes_data_free);
+
+       g_ptr_array_add (backend->priv->notify_changes, ncd);
+
+       if (backend->priv->changes_timeout_id) {
+               if (backend->priv->notify_changes->len > NOTIFY_CHANGES_THRESHOLD) {
+                       g_source_remove (backend->priv->changes_timeout_id);
+                       backend->priv->changes_timeout_id = 0;
+
+                       schedule_notify_changes_thread_locked (backend);
+               }
+       } else {
+               backend->priv->changes_timeout_id = e_named_timeout_add_full (G_PRIORITY_DEFAULT, 
NOTIFY_CHANGES_TIMEOUT,
+                       notify_changes_timeout_cb, e_weak_ref_new (backend), (GDestroyNotify) 
e_weak_ref_free);
+       }
+
+       g_mutex_unlock (&backend->priv->property_lock);
+}
+
 static void
 cal_backend_push_operation (ECalBackend *backend,
                             GSimpleAsyncResult *simple,
@@ -641,6 +846,17 @@ cal_backend_dispose (GObject *object)
                priv->auth_source_changed_handler_id = 0;
        }
 
+       g_mutex_lock (&priv->property_lock);
+       if (priv->changes_timeout_id) {
+               g_source_remove (priv->changes_timeout_id);
+               priv->changes_timeout_id = 0;
+       }
+       if (priv->notify_changes) {
+               g_ptr_array_unref (priv->notify_changes);
+               priv->notify_changes = NULL;
+       }
+       g_mutex_unlock (&priv->property_lock);
+
        g_clear_object (&priv->registry);
        g_clear_object (&priv->data_cal);
        g_clear_object (&priv->proxy_resolver);
@@ -651,7 +867,9 @@ cal_backend_dispose (GObject *object)
        priv->views = NULL;
        g_mutex_unlock (&priv->views_mutex);
 
+       g_mutex_lock (&priv->operation_lock);
        g_hash_table_remove_all (priv->operation_ids);
+       g_mutex_unlock (&priv->operation_lock);
 
        while (!g_queue_is_empty (&priv->pending_operations))
                dispatch_node_free (g_queue_pop_head (&priv->pending_operations));
@@ -672,6 +890,11 @@ cal_backend_finalize (GObject *object)
        g_mutex_clear (&priv->views_mutex);
        g_mutex_clear (&priv->property_lock);
 
+       if (priv->notify_changes) {
+               g_ptr_array_unref (priv->notify_changes);
+               priv->notify_changes = NULL;
+       }
+
        g_free (priv->cache_dir);
 
        g_hash_table_destroy (priv->zone_cache);
@@ -4491,46 +4714,10 @@ void
 e_cal_backend_notify_component_created (ECalBackend *backend,
                                         ECalComponent *component)
 {
-       GList *list, *link;
-
        g_return_if_fail (E_IS_CAL_BACKEND (backend));
        g_return_if_fail (E_IS_CAL_COMPONENT (component));
 
-       list = e_cal_backend_list_views (backend);
-
-       for (link = list; link != NULL; link = g_list_next (link)) {
-               EDataCalView *view = E_DATA_CAL_VIEW (link->data);
-
-               if (e_data_cal_view_component_matches (view, component))
-                       e_data_cal_view_notify_components_added_1 (view, component);
-       }
-
-       g_list_free_full (list, (GDestroyNotify) g_object_unref);
-}
-
-static void
-match_view_and_notify_component (EDataCalView *view,
-                                 ECalComponent *old_component,
-                                 ECalComponent *new_component)
-{
-       gboolean old_match = FALSE, new_match = FALSE;
-
-       if (old_component)
-               old_match = e_data_cal_view_component_matches (view, old_component);
-
-       new_match = e_data_cal_view_component_matches (view, new_component);
-
-       if (old_match && new_match)
-               e_data_cal_view_notify_components_modified_1 (view, new_component);
-       else if (new_match)
-               e_data_cal_view_notify_components_added_1 (view, new_component);
-       else if (old_match) {
-               ECalComponentId *id = e_cal_component_get_id (old_component);
-
-               e_data_cal_view_notify_objects_removed_1 (view, id);
-
-               e_cal_component_id_free (id);
-       }
+       schedule_notify_changes (backend, NOTIFY_CHANGE_KIND_ADD, NULL, component, NULL);
 }
 
 /**
@@ -4551,20 +4738,11 @@ e_cal_backend_notify_component_modified (ECalBackend *backend,
                                          ECalComponent *old_component,
                                          ECalComponent *new_component)
 {
-       GList *list, *link;
-
        g_return_if_fail (E_IS_CAL_BACKEND (backend));
        g_return_if_fail (!old_component || E_IS_CAL_COMPONENT (old_component));
        g_return_if_fail (E_IS_CAL_COMPONENT (new_component));
 
-       list = e_cal_backend_list_views (backend);
-
-       for (link = list; link != NULL; link = g_list_next (link))
-               match_view_and_notify_component (
-                       E_DATA_CAL_VIEW (link->data),
-                       old_component, new_component);
-
-       g_list_free_full (list, (GDestroyNotify) g_object_unref);
+       schedule_notify_changes (backend, NOTIFY_CHANGE_KIND_MODIFY, old_component, new_component, NULL);
 }
 
 /**
@@ -4589,34 +4767,10 @@ e_cal_backend_notify_component_removed (ECalBackend *backend,
                                         ECalComponent *old_component,
                                         ECalComponent *new_component)
 {
-       GList *list, *link;
-
        g_return_if_fail (E_IS_CAL_BACKEND (backend));
        g_return_if_fail (id != NULL);
 
-       if (old_component != NULL)
-               g_return_if_fail (E_IS_CAL_COMPONENT (old_component));
-
-       if (new_component != NULL)
-               g_return_if_fail (E_IS_CAL_COMPONENT (new_component));
-
-       list = e_cal_backend_list_views (backend);
-
-       for (link = list; link != NULL; link = g_list_next (link)) {
-               EDataCalView *view = E_DATA_CAL_VIEW (link->data);
-
-               if (new_component != NULL)
-                       match_view_and_notify_component (
-                               view, old_component, new_component);
-
-               else if (old_component == NULL)
-                       e_data_cal_view_notify_objects_removed_1 (view, id);
-
-               else if (e_data_cal_view_component_matches (view, old_component))
-                       e_data_cal_view_notify_objects_removed_1 (view, id);
-       }
-
-       g_list_free_full (list, (GDestroyNotify) g_object_unref);
+       schedule_notify_changes (backend, NOTIFY_CHANGE_KIND_REMOVE, old_component, new_component, id);
 }
 
 /**