as though holding a red pen and a lock stamp

Found two bugs in peripheral code around cgroup_attach_task while trying to finish up my older project, which is to add cgroup_attach_proc. More on the actual project later; for now:

1. Earlier this year, cpuset was changed to use NODEMASK_ALLOC, to avoid stack-allocating a structure which can be huge on NUMA systems. However, the present usage is rather cavalier in functions that aren't allowed to fail!
2. Last month, the locking order in memcontrol was changed to avoid a potential deadlock... introducing a bit of foot-stepping between it and cpuset.
   

Fortunately, none of these are design-level blockers to the patch series I'm trying to finalize. But the solutions could prove "interesting"...