struct task_struct structure contains about 1700 bytes and this is pretty large. Unfortunately any Linux source code can acces any member of this structure via the current macro and nearly all user context related code will do - source code files and interface definitions (headers).
DDE allocates and initializes one process descriptor for each interface thread. It is leaved untouched except for the addition of special per Thread information, e.g. dde_sema. (see linux/sched.h)