It is possible to have parallel attach operations to the same cpuset in
progress. To avoid possible corruption of single set of DL BW data in
the cpuset structure, we have to disallow parallel attach operations if
DL tasks are present. Attach operations can still proceed in parallel
as long as no DL tasks are involved.
This patch also stores the CPU where DL BW is allocated and free that BW
back to the same CPU in case cpuset_can_attach() is called.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>