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gdbus-codegen: Ensure that generated skeletons are MT-safe

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For example, if setting a property on a skeleton from another thread
than where it was constructed, the idle handler responsible for
emitting the PropertiesChanged() signal could run immediately and
clear skeleton->priv->changed_properties_idle_source causing
g_source_unref() to be called with a NULL pointer. This race was
easily be fixed by adding a lock to the skeleton object.

In addition to fixing this race, also move the code for setting up the
idle handler to a class handler for the GObject::notify signal. This
change allows use of g_object_freeze_notify() and g_object_thaw_notify()
to perform atomic property changes from another thread than the one
that the skeleton was created in.

Signed-off-by: David Zeuthen <davidz@redhat.com>
This commit is contained in:
David Zeuthen 2011-05-15 11:45:37 -04:00
parent 2122191595
commit 11e01802ab
2 changed files with 74 additions and 30 deletions
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11
docs/reference/gio/gdbus-codegen.xml
View File

@ -711,12 +711,17 @@ on_handle_hello_world (MyAppFrobber *object,
<para>
To facilitate atomic changesets (multiple properties changing at
the same time), #GObject::notify signals are queued up when
received. The queue is drained in an idle handler and will cause
emissions of the <ulink
received. The queue is drained in an idle handler (which is called from the
<link linkend="g-main-context-push-thread-default">thread-default main loop</link>
of the thread where the skeleton object was
contructed) and will cause emissions of the <ulink
url="http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties">org.freedesktop.DBus.Properties::PropertiesChanged</ulink>
signal with all the properties that have changed. Use
g_dbus_interface_skeleton_flush() or
g_dbus_object_skeleton_flush() to empty the queue immediately.
g_dbus_object_skeleton_flush() to empty the queue
immediately. Use g_object_freeze_notify() and
g_object_thaw_notify() for atomic changesets if on a different
thread.
</para>
</refsect2>
</refsect1>

55
gio/gdbus-codegen/codegen.py
View File

@ -1845,6 +1845,7 @@ class CodeGenerator:
' GList *changed_properties;\n'
' GSource *changed_properties_idle_source;\n'
' GMainContext *context;\n'
' GMutex *lock;\n'
'};\n'
'\n'%i.camel_name)
@ -2054,12 +2055,19 @@ class CodeGenerator:
%(i.name_lower))
if len(i.properties) > 0:
self.c.write(' %sSkeleton *skeleton = %s%s_SKELETON (_skeleton);\n'
' gboolean emit_changed = FALSE;\n'
'\n'
' g_mutex_lock (skeleton->priv->lock);\n'
' if (skeleton->priv->changed_properties_idle_source != NULL)\n'
' {\n'
' g_source_destroy (skeleton->priv->changed_properties_idle_source);\n'
' skeleton->priv->changed_properties_idle_source = NULL;\n'
' _%s_emit_changed (skeleton);\n'
' emit_changed = TRUE;\n'
' }\n'
' g_mutex_unlock (skeleton->priv->lock);\n'
'\n'
' if (emit_changed)\n'
' _%s_emit_changed (skeleton);\n'
%(i.camel_name, i.ns_upper, i.name_upper, i.name_lower))
self.c.write('}\n'
'\n')
@ -2118,11 +2126,13 @@ class CodeGenerator:
self.c.write(' g_source_destroy (skeleton->priv->changed_properties_idle_source);\n')
self.c.write(' if (skeleton->priv->context != NULL)\n')
self.c.write(' g_main_context_unref (skeleton->priv->context);\n')
self.c.write(' g_mutex_free (skeleton->priv->lock);\n')
self.c.write(' G_OBJECT_CLASS (%s_skeleton_parent_class)->finalize (object);\n'
'}\n'
'\n'%(i.name_lower))
# property accessors (TODO: generate PropertiesChanged signals in setter)
if len(i.properties) > 0:
self.c.write('static void\n'
'%s_skeleton_get_property (GObject *object,\n'
' guint prop_id,\n'
@ -2131,11 +2141,13 @@ class CodeGenerator:
'{\n'%(i.name_lower))
self.c.write(' %sSkeleton *skeleton = %s%s_SKELETON (object);\n'
' g_assert (prop_id != 0 && prop_id - 1 < %d);\n'
' g_mutex_lock (skeleton->priv->lock);\n'
' g_value_copy (&skeleton->priv->properties->values[prop_id - 1], value);\n'
' g_mutex_unlock (skeleton->priv->lock);\n'
%(i.camel_name, i.ns_upper, i.name_upper, len(i.properties)))
self.c.write('}\n'
'\n')
if len(i.properties) > 0:
# if property is already scheduled then re-use entry.. though it could be
# that the user did
#
@ -2157,6 +2169,8 @@ class CodeGenerator:
' GVariantBuilder builder;\n'
' GVariantBuilder invalidated_builder;\n'
' guint num_changes;\n'
'\n'
' g_mutex_lock (skeleton->priv->lock);\n'
' g_variant_builder_init (&builder, G_VARIANT_TYPE ("a{sv}"));\n'
' g_variant_builder_init (&invalidated_builder, G_VARIANT_TYPE ("as"));\n'
' for (l = skeleton->priv->changed_properties, num_changes = 0; l != NULL; l = l->next)\n'
@ -2195,9 +2209,11 @@ class CodeGenerator:
self.c.write(' g_list_free (skeleton->priv->changed_properties);\n')
self.c.write(' skeleton->priv->changed_properties = NULL;\n')
self.c.write(' skeleton->priv->changed_properties_idle_source = NULL;\n')
self.c.write(' g_mutex_unlock (skeleton->priv->lock);\n')
self.c.write(' return FALSE;\n'
'}\n'
'\n')
# holding lock while being called
self.c.write('static void\n'
'_%s_schedule_emit_changed (%sSkeleton *skeleton, const _ExtendedGDBusPropertyInfo *info, guint prop_id, const GValue *orig_value)\n'
'{\n'
@ -2223,7 +2239,22 @@ class CodeGenerator:
' g_value_init (&cp->orig_value, G_VALUE_TYPE (orig_value));\n'
' g_value_copy (orig_value, &cp->orig_value);\n'
' }\n'
' if (skeleton->priv->changed_properties_idle_source == NULL)\n'
'}\n'
'\n'
%())
# Postpone setting up the refresh source until the ::notify signal is emitted as
# this allows use of g_object_freeze_notify()/g_object_thaw_notify() ...
# This is useful when updating several properties from another thread than
# where the idle will be emitted from
self.c.write('static void\n'
'%s_skeleton_notify (GObject *object,\n'
' GParamSpec *pspec)\n'
'{\n'
' %sSkeleton *skeleton = %s%s_SKELETON (object);\n'
' g_mutex_lock (skeleton->priv->lock);\n'
' if (skeleton->priv->changed_properties != NULL &&\n'
' skeleton->priv->changed_properties_idle_source == NULL)\n'
' {\n'
' skeleton->priv->changed_properties_idle_source = g_idle_source_new ();\n'
' g_source_set_priority (skeleton->priv->changed_properties_idle_source, G_PRIORITY_DEFAULT);\n'
@ -2231,18 +2262,21 @@ class CodeGenerator:
' g_source_attach (skeleton->priv->changed_properties_idle_source, skeleton->priv->context);\n'
' g_source_unref (skeleton->priv->changed_properties_idle_source);\n'
' }\n'
' g_mutex_unlock (skeleton->priv->lock);\n'
'}\n'
'\n'
%(i.name_lower))
%(i.name_lower, i.camel_name, i.ns_upper, i.name_upper, i.name_lower))
self.c.write('static void\n'
'%s_skeleton_set_property (GObject *object,\n'
' guint prop_id,\n'
' const GValue *value,\n'
' GParamSpec *pspec)\n'
'{\n'%(i.name_lower))
if len(i.properties) > 0:
self.c.write(' %sSkeleton *skeleton = %s%s_SKELETON (object);\n'
' g_assert (prop_id != 0 && prop_id - 1 < %d);\n'
' g_mutex_lock (skeleton->priv->lock);\n'
' g_object_freeze_notify (object);\n'
' if (!_g_value_equal (value, &skeleton->priv->properties->values[prop_id - 1]))\n'
' {\n'
' if (g_dbus_interface_skeleton_get_connection (G_DBUS_INTERFACE_SKELETON (skeleton)) != NULL)\n'
@ -2250,6 +2284,8 @@ class CodeGenerator:
' g_value_copy (value, &skeleton->priv->properties->values[prop_id - 1]);\n'
' g_object_notify_by_pspec (object, pspec);\n'
' }\n'
' g_mutex_unlock (skeleton->priv->lock);\n'
' g_object_thaw_notify (object);\n'
%(i.camel_name, i.ns_upper, i.name_upper, len(i.properties), i.name_lower, i.name_lower))
self.c.write('}\n'
'\n')
@ -2259,6 +2295,7 @@ class CodeGenerator:
'{\n'
' skeleton->priv = G_TYPE_INSTANCE_GET_PRIVATE (skeleton, %sTYPE_%s_SKELETON, %sSkeletonPrivate);\n'
%(i.name_lower, i.camel_name, i.ns_upper, i.name_upper, i.camel_name))
self.c.write(' skeleton->priv->lock = g_mutex_new ();\n')
self.c.write(' skeleton->priv->context = g_main_context_get_thread_default ();\n')
self.c.write(' if (skeleton->priv->context != NULL)\n')
self.c.write(' g_main_context_ref (skeleton->priv->context);\n')
@ -2281,10 +2318,12 @@ class CodeGenerator:
'\n'
' gobject_class = G_OBJECT_CLASS (klass);\n'
' gobject_class->finalize = %s_skeleton_finalize;\n'
' gobject_class->get_property = %s_skeleton_get_property;\n'
' gobject_class->set_property = %s_skeleton_set_property;\n'
'\n'%(i.name_lower, i.camel_name, i.camel_name, i.name_lower, i.name_lower, i.name_lower))
%(i.name_lower, i.camel_name, i.camel_name, i.name_lower))
if len(i.properties) > 0:
self.c.write(' gobject_class->get_property = %s_skeleton_get_property;\n'
' gobject_class->set_property = %s_skeleton_set_property;\n'
' gobject_class->notify = %s_skeleton_notify;\n'
'\n'%(i.name_lower, i.name_lower, i.name_lower))
self.c.write('\n'
' %s_override_properties (gobject_class, 1);\n'%(i.name_lower))
self.c.write('\n'