Fixed #21217 -- Avoid connecting `(pre|post)_init` signals to abstract senders.

2 files changed, 7 insertions, 5 deletions

diff --git a/django/contrib/contenttypes/generic.py b/django/contrib/contenttypes/generic.py
index b34847b81d..1fdb1f1894 100644
--- a/django/contrib/contenttypes/generic.py
+++ b/django/contrib/contenttypes/generic.py
@@ -14,7 +14,7 @@ from django.db.models.fields.related import ForeignObject, ForeignObjectRel
 from django.db.models.related import PathInfo
 from django.db.models.sql.where import Constraint
 from django.forms import ModelForm, ALL_FIELDS
-from django.forms.models import (BaseModelFormSet, modelformset_factory, save_instance,
+from django.forms.models import (BaseModelFormSet, modelformset_factory,
     modelform_defines_fields)
 from django.contrib.admin.options import InlineModelAdmin, flatten_fieldsets
 from django.contrib.contenttypes.models import ContentType
@@ -46,10 +46,10 @@ class GenericForeignKey(six.with_metaclass(RenameGenericForeignKeyMethods)):
         self.cache_attr = "_%s_cache" % name
         cls._meta.add_virtual_field(self)
 
-        # For some reason I don't totally understand, using weakrefs here doesn't work.
-        signals.pre_init.connect(self.instance_pre_init, sender=cls, weak=False)
+        # Only run pre-initialization field assignment on non-abstract models
+        if not cls._meta.abstract:
+            signals.pre_init.connect(self.instance_pre_init, sender=cls)
 
-        # Connect myself as the descriptor for this field
         setattr(cls, name, self)
 
     def instance_pre_init(self, signal, sender, args, kwargs, **_kwargs):
diff --git a/django/db/models/fields/files.py b/django/db/models/fields/files.py
index 61e3eebf49..557ec6ec8a 100644
--- a/django/db/models/fields/files.py
+++ b/django/db/models/fields/files.py
@@ -358,7 +358,9 @@ class ImageField(FileField):
         # Attach update_dimension_fields so that dimension fields declared
         # after their corresponding image field don't stay cleared by
         # Model.__init__, see bug #11196.
-        signals.post_init.connect(self.update_dimension_fields, sender=cls)
+        # Only run post-initialization dimension update on non-abstract models
+        if not cls._meta.abstract:
+            signals.post_init.connect(self.update_dimension_fields, sender=cls)
 
     def update_dimension_fields(self, instance, force=False, *args, **kwargs):
         """