Hi,
the DDE models a SMP-like setup, whereas each ddekit_thread is supposed to run on a dedicated CPU. For each IRQ, there is a dedicated ddekit_thread. As far as I understand it, disabling hard IRQs in any other ddekit_thread than the IRQ-handler threads has no effect, because they won't receive IRQs anyway. For an IRQ handler thread, it also has no effect, because it only runs when it is handling an interrupt, and won't receive any further IRQs while handling one.
Best regards,
Dirk.