On Mon, Jul 18, 2022 at 10:00:26PM -0400, Eric Farman wrote: > > + if (!drv->get_available) { > > + if (atomic_dec_and_test(&parent->available_instances)) > > { > > Ah, subtle change between v5 and v6 to use atomics. As vfio-ccw only > has 1 available instance per mdev, this breaks us. Did you mean > atomic_dec_if_positive() ? Yes, this should have been atomic_dec_if_positive. Or just an open coded atomic_dec + atomic_read a the only reason to use an atomic is for the sysfs file that reads it outside the lock.