mbox series

[0/2] Fix test-char reference counting bug

Message ID 20201215224133.3545901-1-ehabkost@redhat.com
Headers show
Series Fix test-char reference counting bug | expand

Message

Eduardo Habkost Dec. 15, 2020, 10:41 p.m. UTC 
This series addresses a bug that seems to be the cause of the
following crash, that is reported by Patchew and other CI systems
once in a while:

  Running test test-char
  Unexpected error in object_property_try_add() at ../qom/object.c:1220: attempt to add duplicate property 'serial-id' to object (type 'container')
  ERROR test-char - too few tests run (expected 38, got 9)
  make: *** [run-test-86] Error 1

This is what seems to be happening:

- char_file_test_internal() creates chr using qemu_chardev_new().
- qemu_chardev_new() automatically assigns ID, adds
  chardev to the QOM tree.
- char_file_test_internal() does _not_ own the reference
  to the created object.
- char_file_test_internal() incorrectly calls object_unref().
- object is freed but, but /containers now has a dangling
  pointer.
- char_serial_test() creates a chardev with ID "serial-id", and
  it ends up being allocated at the same address as the old
  object.
- char_serial_test() correctly calls object_unparent().
- object_property_del_child() looks for the right child property
  in the hashtable, finds the dangling pointer with the same
  address, removes the wrong property, leaves a dangling
  "serial-id" property.
- New object is created by char_serial_test() with ID "serial-id".
- object_property_try_add_child() will fail because of the
  dangling "serial-id" property.

Eduardo Habkost (2):
  test-char: Destroy chardev correctly at char_file_test_internal()
  qom: Assert that objects being destroyed have no parent

 qom/object.c      | 1 +
 tests/test-char.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)