Comment 3 for bug 1589923

Fixed in stable-2.6 branch in

commit 510531ea442a02048b1837fcf574d03559b38c9e
Author: Daniel P. Berrange <email address hidden>
Date: Tue Jun 7 12:27:51 2016 +0100

    io: remove mistaken call to object_ref on QTask

    The QTask struct is just a standalone struct, not a QOM Object,
    so calling object_ref() on it is not appropriate. This results
    in mangling the 'destroy' field in the QTask struct, causing
    the later call to qtask_free() to try to call the function
    at address 0x1, with predictably segfault happy results.

    There is in fact no need for ref counting with QTask, as the
    call to qtask_abort() or qtask_complete() will automatically
    free associated memory.

    This fixes the crash shown in

      https://bugs.launchpad.net/qemu/+bug/1589923

    Reviewed-by: Eric Blake <email address hidden>
    Signed-off-by: Daniel P. Berrange <email address hidden>
    (cherry picked from commit bc35d51077b33e68a0ab10a057f352747214223f)
    Signed-off-by: Michael Roth <email address hidden>