There is a technique for eliminating the long pauses from rebuilding called "incremental global rebuilding". The big idea is that the new structure is built piece-by-piece, taking a few building steps for each update to the existing structure. The new construction is finished before the existing structure fills up (or empties out, for deletes). Depending on the variant, updates may be applied as the new structure is being built, batched to be applied later, or applied in a secondary "ghost" structure.
It has been used in dozens of data structures, and was, I think, made famous by a series of papers by Overmars and co-authors in the early 80s. He wrote a book about related techniques called "The Design of Dynamic Data Structures".
Does this technique not apply to resizing hash tables in a concurrent kernel?