Problem:

As the comment above the calculation of max_pull in the function states, 
there is a need to ensure that negative results of the subtractions do 
not wrap around to large numbers.  This has not been implemented for the 
(max_load - busiest_load_per_task) expression and the possible 
consequences are for undesirable movement of tasks from one group to 
another group. E.g. consider a numa system with two nodes, each
node containing four processors.  If there are two processes in node-0 
and with node-1 being completely idle,  one of those processes will be 
moved to node-1 whereas the desired behavior is to retain those two 
processes in node-0.

Fix:

Make sure that max_load is greater than busiest_load_per_task before 
making the calculation.  If it isn't max_pull will be zero and we skip 
directly to out_balanced.

Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>

-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce