If this occurs again, please try:
echo 0 | sudo tee /sys/module/spl/parameters/spl_taskq_thread_dynamic
..and see if this stops the issue from repeating.
If this occurs again, please try:
echo 0 | sudo tee /sys/module/ spl/parameters/ spl_taskq_ thread_ dynamic
..and see if this stops the issue from repeating.